58 results on '"Salata JJ"'
Search Results
2. Halide ion effects on human Ether-à-go-go related gene potassium channel properties.
- Author
-
Zeng H, Balasubramanian B, Penniman JR, Kinose F, Salata JJ, and Lagrutta A
- Subjects
- Animals, CHO Cells, Cricetinae, Cricetulus, Drug Evaluation, Preclinical methods, ERG1 Potassium Channel, Flow Cytometry methods, Flow Injection Analysis methods, Ion Channel Gating drug effects, Ions, Membrane Potentials drug effects, Ether-A-Go-Go Potassium Channels antagonists & inhibitors, Ether-A-Go-Go Potassium Channels physiology, Halogens pharmacology, Ion Channel Gating physiology, Membrane Potentials physiology, Patch-Clamp Techniques methods, Potassium Channel Blockers pharmacology
- Abstract
The human Ether-à-go-go related gene (hERG) potassium channel has been widely used to counter screen potential pharmaceuticals as a biomarker to predict clinical QT prolongation. Thus, higher throughput assays of hERG are valuable for early in vitro screening of drug candidates to minimize failure in later-stage drug development due to this potentially adverse cardiac risk. We have developed a novel method utilizing potassium fluoride to improve throughput of hERG counter screening with an automated patch clamp system, PatchXpress 7000A. In that method, ∼50% substitution of internal Cl(-) with F(-) greatly increases success rate without substantially altering the biophysical properties of the hERG channel or compromising data quality. However, effect of F(-) or other halide ions on hERG channel properties has not been studied in detail. In this study, we examined effects of complete replacement of Cl(-) in internal solution with halide ions, F(-), or Br(-). We found that (1) F(-) slightly shifts the voltage dependence of hERG channel activation to more positive voltages, while Br(-) shifts it to more negative voltages; (2) Br(-) shifts to more positive voltages both the inactivation-voltage relationship and the peak position of channel full activation of hERG; (3) F(-) slows hERG activation, while both F(-) and Br(-) make the channel close faster; (4) neither F(-) nor Br(-) have any effect on hERG inactivation kinetics. In conclusion, compared to Cl(-), F(-) has subtle effect on hERG activation, while Br(-) has distinct effects on certain, but not all biophysical properties of hERG channel.
- Published
- 2013
- Full Text
- View/download PDF
3. The anesthetized guinea pig: an effective early cardiovascular derisking and lead optimization model.
- Author
-
Morissette P, Nishida M, Trepakova E, Imredy J, Lagrutta A, Chaves A, Hoagland K, Hoe CM, Zrada MM, Travis JJ, Zingaro GJ, Gerenser P, Friedrichs G, and Salata JJ
- Subjects
- Anesthesia, Animals, Electrocardiography, Guinea Pigs, Humans, Ion Channels metabolism, Male, Models, Animal, Predictive Value of Tests, Reproducibility of Results, Sensitivity and Specificity, Telemetry, Toxicity Tests methods, Drug Design, Ion Channels drug effects, Long QT Syndrome chemically induced
- Abstract
Introduction: In recent years, the anesthetized guinea pig has been used increasingly to evaluate the cardiovascular effects of drug-candidate molecules during lead optimization prior to conducting longer, more resource intensive safety pharmacology and toxicology studies. The aim of these studies was to evaluate the correlations between pharmacologically-induced ECG changes in the anesthetized cardiovascular guinea pig (CVGP) with ECG changes in conscious non-rodent telemetry models, human clinical studies and effects on key cardiac ion channels., Methods: We compared the effects of 38 agents on ion channel inhibition to their ECG effects in the CVGP. 26 of these agents were also evaluated in non-rodent telemetry and compared to the results in the CVGP., Results: The CVGP was highly sensitive for detecting QTc, PR and QRS interval prolongation mediated by inhibition of hERG, hCav1.2 and hNav1.5, respectively. There were robust correlations between ion channel inhibitory potencies and the free plasma concentrations (Cu) producing prolongation of the QTc, PR or QRS interval. Further evaluation showed that ECG changes in the CVGP were predictive of their effects on the QTc, PR and QRS intervals in non-rodent telemetry models with 92%, 92% and 100% accuracy, respectively. The CVGP proved to be 100% specific and 88%, 75% and 100% sensitive for QTc, PR and QRS interval prolongation, respectively. Similarly, the Cu that prolonged the QTc, PR and QRS in CVGP and humans correlated well., Discussion: The CVGP is a sensitive model for assessing QTc, PR and QRS prolongation elicited by effects on hERG, hCav1.2 and hNav1.5, respectively. ECG changes in the CVGP are predictive of changes in non-rodent telemetry models and in humans (QTc). ECG parameters can be reliably evaluated with the CVGP model which increases the efficiency of CV derisking. Importantly, the design and implementation of this model is consistent with the "3Rs" for animal research., (Copyright © 2013 Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
4. Assessing use-dependent inhibition of the cardiac Na(+/-) current (I(Na)) in the PatchXpress automated patch clamp.
- Author
-
Penniman JR, Kim DC, Salata JJ, and Imredy JP
- Subjects
- Action Potentials drug effects, Animals, Dose-Response Relationship, Drug, Flecainide pharmacology, Guinea Pigs, HEK293 Cells, Humans, Lidocaine pharmacology, Mexiletine pharmacology, Muscle Proteins metabolism, Myocytes, Cardiac drug effects, NAV1.5 Voltage-Gated Sodium Channel, Sodium Channels metabolism, Muscle Proteins antagonists & inhibitors, Myocardium metabolism, Myocytes, Cardiac physiology, Patch-Clamp Techniques, Sodium Channel Blockers pharmacology
- Abstract
Introduction: The cardiac Na+ current (I(Na)) underlies the rapid depolarization of the cardiac myocyte, and block of the current slows cardiac conduction and increases the risk of ventricular arrhythmia. A feature of Na+ channel block termed use-dependence is important to the assessment of blocking potency. We developed a robust automated patch clamp assay to rapidly and routinely assess the use-dependent block of I(Na) by drug candidates. The assay clarifies whether drug candidates block more potently at increased heart rates and provides a quantitative score of use-dependence., Methods: A use-dependent cardiac I(Na) assay was implemented on the PatchXpress 7000A, an automated whole-cell patch clamp device, using a HEK cell line stably expressing the human cardiac Na+ channel, Na(V)1.5. Stable recordings lasting up to 30 minutes were achieved by selection of holding potential (-100 mV) as well as an appropriate osmotic gradient to prevent time-dependent loss of cell capacitance and current. The final protocol allows evaluation of I(Na) inhibition at three pulsing rates at three test concentrations for each recorded cell., Results: IC(50) values obtained for three standard I(Na) blockers lidocaine, mexiletine, and flecainide, at pulsing frequencies of 0.2 Hz, 1 Hz, and 3 Hz, were compared to IC(50) values obtained with conventional pipette patch clamp of the Na(V)1.5 cell line and of guinea pig cardiac myocytes using matched voltage protocols and pulsing rates. Absolute potencies were well correlated only under conditions of matched holding potential and fell within an approximately three-fold window. While absolute potencies could vary widely with holding potential, the fold increases in potency with increases in pulsing rates were less prone to variation of the holding potential., Discussion: Use-dependence of cardiac Na+ channel block can be rapidly assessed in the PatchXpress platform and quantified at early stages of drug development to guide lead optimization., (2010. Published by Elsevier Inc.)
- Published
- 2010
- Full Text
- View/download PDF
5. Discovery of triarylethanolamine inhibitors of the Kv1.5 potassium channel.
- Author
-
Beshore DC, Liverton NJ, McIntyre CJ, Claiborne CF, Libby B, Culberson JC, Salata JJ, Regan CP, Lynch JJ, Kiss L, Spencer RH, Kane SA, White RB, Yeh S, Hartman GD, and Dinsmore CJ
- Subjects
- Animals, Dose-Response Relationship, Drug, Drug Discovery, Drug Evaluation, Preclinical, Ethanolamines chemistry, Humans, Potassium Channel Blockers chemistry, Structure-Activity Relationship, Ethanolamines pharmacology, Potassium Channel Blockers pharmacology, Potassium Channels, Voltage-Gated antagonists & inhibitors
- Abstract
A series of triarylethanolamine inhibitors of the Kv1.5 potassium channel have been prepared and evaluated for their effects in vitro and in vivo. The structure-activity relationship (SAR) studies described herein led to the development of potent, selective and orally active inhibitors of Kv1.5., (Copyright 2010 Elsevier Ltd. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
6. Optimization of Ca(v)1.2 screening with an automated planar patch clamp platform.
- Author
-
Balasubramanian B, Imredy JP, Kim D, Penniman J, Lagrutta A, and Salata JJ
- Subjects
- Animals, Barium metabolism, Cell Line, Collagenases pharmacology, Dose-Response Relationship, Drug, Electrophysiology, Guinea Pigs, Heart Ventricles cytology, Humans, Inhibitory Concentration 50, Kidney cytology, Male, Myocytes, Cardiac drug effects, Patch-Clamp Techniques methods, Peptide Hydrolases pharmacology, Temperature, Time Factors, Transfection, Trypsin pharmacology, 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester pharmacology, Calcium Channel Agonists pharmacology, Calcium Channel Blockers pharmacology, Calcium Channels, L-Type drug effects, Drug Evaluation, Preclinical instrumentation, Nifedipine pharmacology, Patch-Clamp Techniques instrumentation
- Abstract
Introduction: Ca(v)1.2 channels play an important role in shaping the cardiac action potential. Screening pharmaceutical compounds for Ca(v)1.2 block is very important in developing drugs without cardiac liability. Ca(v)1.2 screening has been traditionally done using fluorescence assays, but these assays have some limitations. Patch clamping is considered the gold standard for ion channel studies, but is very labor intensive. The purpose of this study was to develop a robust medium throughput Ca(v)1.2 screening assay in PatchXpress 7000A by optimizing cell isolation conditions, recording solutions and experimental parameters. Under the conditions established, structurally different standard Ca(v)1.2 antagonists and an agonist were tested., Methods: HEK-293 cells stably transfected with hCa(v)1.2 L-type Ca channel were used. For experiments, cells were isolated using 0.05% Trypsin. Currents were recorded in the presence of 30 mM extracellular Ba2+ and low magnesium intracellular recording solution to minimize rundown. Ca(v)1.2 currents were elicited from a holding potential of -60 mV at 0.05 Hz to increase pharmacological sensitivity and minimize rundown. Test compounds were applied at increasing concentrations for 5 min followed by a brief washout., Results: Averaged peak Ca(v)1.2 current amplitudes were increased from 10 pA/pF to 15 pA/pF by shortening cell incubation and trypsin exposure time from 2.5 min at 37 degrees C to 1 min at room temperature and adding 0.2 mM cAMP to the intracellular solution. Rundown was minimized from 2%/min to 0.5%/min by reducing the intracellular free Mg2+ from 2.7 mM to 0.2 mM and adding 100 nM Ca2+. Under the established conditions, we tested 8 structurally different antagonists and an agonist. The IC(50) values obtained ranked well against published values and results obtained using traditional clamp experiments performed in parallel using the expressed cell line and native myocytes., Discussion: This assay can be used as a reliable pharmacological screening tool for Ca(v)1.2 block to assess compounds for cardiac liability during lead optimization.
- Published
- 2009
- Full Text
- View/download PDF
7. Modeling of the adrenergic response of the human IKs current (hKCNQ1/hKCNE1) stably expressed in HEK-293 cells.
- Author
-
Imredy JP, Penniman JR, Dech SJ, Irving WD, and Salata JJ
- Subjects
- Adenylyl Cyclases metabolism, Adrenergic beta-Agonists pharmacology, Cell Line, Colforsin pharmacology, Cyclic AMP analogs & derivatives, Cyclic AMP metabolism, Cyclic AMP pharmacology, Enzyme Activators pharmacology, Humans, Isoproterenol pharmacology, KCNQ1 Potassium Channel drug effects, KCNQ1 Potassium Channel genetics, Kinetics, Membrane Potentials, Models, Cardiovascular, Potassium metabolism, Potassium Channels, Voltage-Gated drug effects, Potassium Channels, Voltage-Gated genetics, Receptors, Adrenergic, beta drug effects, Recombinant Proteins metabolism, Temperature, Thionucleotides pharmacology, Transfection, Ion Channel Gating drug effects, KCNQ1 Potassium Channel metabolism, Potassium Channels, Voltage-Gated metabolism, Receptors, Adrenergic, beta metabolism
- Abstract
Stable coexpression of human (h)KCNQ1 and hKCNE1 in human embryonic kidney (HEK)-293 cells reconstitutes a nativelike slowly activating delayed rectifier K+ current (HEK-I(Ks)), allowing beta-adrenergic modulation of the current by stimulation of endogenous receptors in the host cell line. HEK-I(Ks) was enhanced two- to fourfold by isoproterenol (EC50 = 13 nM), forskolin (10 microM), or 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (50 microM), indicating an intact cAMP-dependent ion channel-regulating pathway analogous to the PKA-dependent regulation observed in native cardiac myocytes. Activation kinetics of HEK-I(Ks) were accurately fit with a novel modified second-order Hodgkin-Huxley (H-H) gating model incorporating a fast and a slow gate, each independent of each other in scale and adrenergic response, or a "heterodimer" model. Macroscopically, beta-adrenergic enhancement shifted the current activation threshold to more negative potentials and accelerated activation kinetics while leaving deactivation kinetics relatively unaffected. Modeling of the current response using the H-H model indicated that observed changes in gating could be explained by modulation of the opening rate of the fast gate. Under control conditions at nearly physiological temperatures (35 degrees C), rate-dependent accumulation of HEK-I(Ks) was observed only at pulse frequencies exceeding 3 Hz. Rate-dependent accumulation of I(Ks) at high pulsing rate had two phases, an initial staircaselike effect followed by a slower, incremental accumulation phase. These phases are readily interpreted in the context of a heterodimeric H-H model with two independent gates with differing closing rates. In the presence of isoproterenol after normalizing for its tonic effects, rate-dependent accumulation of HEK-I(Ks) appeared at lower pulse frequencies and was slightly enhanced (approximately 25%) over control.
- Published
- 2008
- Full Text
- View/download PDF
8. Scientific review and recommendations on preclinical cardiovascular safety evaluation of biologics.
- Author
-
Vargas HM, Bass AS, Breidenbach A, Feldman HS, Gintant GA, Harmer AR, Heath B, Hoffmann P, Lagrutta A, Leishman D, McMahon N, Mittelstadt S, Polonchuk L, Pugsley MK, Salata JJ, and Valentin JP
- Subjects
- Humans, Biological Products adverse effects, Cardiovascular Diseases chemically induced, Drug Evaluation, Preclinical methods
- Abstract
Biological therapeutic agents (biologicals), such as monoclonal antibodies (mAbs), are increasingly important in the treatment of human disease, and many types of biologicals are in clinical development. During preclinical drug development, cardiovascular safety pharmacology studies are performed to assess cardiac safety in accord with the ICH S7A and S7B regulations that guide these studies. The question arises, however, whether or not it is appropriate to apply these guidelines, which were devised primarily to standardize small molecule drug testing, to the cardiovascular evaluation of biologicals. We examined the scientific literature and formed a consensus of scientific opinion to determine if there is a rational basis for conducting an in vitro hERG assay as part of routine preclinical cardiovascular safety testing for biologicals. We conclude that mAb therapeutics have very low potential to interact with the extracellular or intracellular (pore) domains on hERG channel and, therefore, are highly unlikely to inhibit hERG channel activity based on their targeted, specific binding properties. Furthermore, mAb are large molecules (>140,000 Da) that cannot cross plasma membranes and therefore would be unable to access and block the promiscuous inner pore of the hERG channel, in contrast with typical small molecule drugs. Consequently, we recommend that it is not appropriate to conduct an in vitro hERG assay as part of a preclinical strategy for assessing the heart rate corrected QT interval (QTc) prolongation risk of mAbs and other types of biologicals. It is more appropriate to assess QTc risk by integrating cardiovascular endpoints into repeat-dose general toxicology studies performed in an appropriate non-rodent species. These recommendations should help shape future regulatory strategy and discussions for the cardiovascular safety pharmacology testing of mAbs as well as other biologicals and provide guidance for the preclinical cardiovascular evaluation of such agents.
- Published
- 2008
- Full Text
- View/download PDF
9. Improved throughput of PatchXpress hERG assay using intracellular potassium fluoride.
- Author
-
Zeng H, Penniman JR, Kinose F, Kim D, Trepakova ES, Malik MG, Dech SJ, Balasubramanian B, and Salata JJ
- Subjects
- Animals, CHO Cells, Cell Membrane drug effects, Cricetinae, Cricetulus, Data Interpretation, Statistical, Electrophysiology, Drug Evaluation, Preclinical methods, Ether-A-Go-Go Potassium Channels drug effects, Fluorides, Patch-Clamp Techniques methods, Potassium Channel Blockers pharmacology, Potassium Compounds
- Abstract
Blockade of the human ether-a-go-go-related gene (hERG) potassium channel, with a consequent possibility of QT prolongation and increased susceptibility to a characteristic polymorphic ventricular arrhythmia, torsade de pointes, is an important cause of withdrawal of drugs from the market. In the aftermath of recent drug withdrawals, regulatory agencies now require in vitro hERG screening of all pharmaceutical compounds that are targeted for human use. To minimize the potential for failure in later-stage drug development, many pharmaceutical and biotechnology companies have begun to use automated patch clamp systems with higher throughput than conventional manual patch-clamp techniques to conduct routine functional hERG screening during drug discovery and early development. We have optimized an automated patch-clamp hERG screening method for the PatchXpress 7000A system (Molecular Devices, Sunnyvale, CA) using potassium fluoride (KF) in the internal recording solution. In this study we show that (1) the biophysical and pharmacological properties of hERG current recorded with KF are similar to those with standard potassium chloride solutions, (2) use of KF significantly improves the success rate of hERG screening using PatchXpress without compromising data quality, and (3) utilization of KF can significantly increase the throughput of hERG screening with PatchXpress.
- Published
- 2008
- Full Text
- View/download PDF
10. The hERG channel and risk of drug-acquired cardiac arrhythmia: an overview.
- Author
-
Lagrutta AA, Trepakova ES, and Salata JJ
- Subjects
- Animals, Arrhythmias, Cardiac genetics, Arrhythmias, Cardiac physiopathology, Electrocardiography, Ether-A-Go-Go Potassium Channels chemistry, Ether-A-Go-Go Potassium Channels genetics, Humans, Risk Factors, Structure-Activity Relationship, Arrhythmias, Cardiac drug therapy, Arrhythmias, Cardiac metabolism, Drug Evaluation, Preclinical, Ether-A-Go-Go Potassium Channels metabolism
- Abstract
This review summarizes current knowledge of the cardiac rapidly activating delayed rectifier potassium current (I(Kr)), and its connection to drug-acquired QT prolongation and the associated risk of ventricular arrhythmia and fibrillation. The molecular characterization of hERG as the structural correlate of I(Kr) and the link between inherited long QT and the KCNH2 gene (hERG), have facilitated mechanistic studies of drug-acquired QT prolongation. The development of high throughput assays to evaluate drug effects on hERG has provided an avenue to determine structure activity relations (SAR) within chemical series. More than 10 years of collective data and structural considerations support the notion that hERG is an unusually promiscuous target among potassium channels, but that defining SAR within a chemical series is a viable strategy to reduce or eliminate hERG activity. Despite a critical need to minimize drug effects on hERG, one should always keep in mind that hERG is not the only structural correlate of QT prolongation, and that QT prolongation is a sub-optimal biomarker for ventricular arrhythmia and fibrillation.
- Published
- 2008
- Full Text
- View/download PDF
11. Kinesin spindle protein (KSP) inhibitors. Part 7: Design and synthesis of 3,3-disubstituted dihydropyrazolobenzoxazines as potent inhibitors of the mitotic kinesin KSP.
- Author
-
Garbaccio RM, Tasber ES, Neilson LA, Coleman PJ, Fraley ME, Olson C, Bergman J, Torrent M, Buser CA, Rickert K, Walsh ES, Hamilton K, Lobell RB, Tao W, South VJ, Diehl RE, Davide JP, Yan Y, Kuo LC, Li C, Prueksaritanont T, Fernandez-Metzler C, Mahan EA, Slaughter DE, Salata JJ, Kohl NE, Huber HE, and Hartman GD
- Subjects
- Animals, Benzoxazines chemical synthesis, Benzoxazines pharmacokinetics, Cell Line, Dogs, Humans, Hydrogen chemistry, Molecular Structure, Structure-Activity Relationship, Benzoxazines chemistry, Benzoxazines pharmacology, Drug Design, Kinesins antagonists & inhibitors, Kinesins metabolism, Mitosis drug effects, Pyrazoles chemistry
- Abstract
Observations from two structurally related series of KSP inhibitors led to the proposal and discovery of dihydropyrazolobenzoxazines that possess ideal properties for cancer drug development. The synthesis and characterization of this class of inhibitors along with relevant pharmacokinetic and in vivo data are presented. The synthesis is highlighted by a key [3+2] cycloaddition to form the pyrazolobenzoxazine core followed by diastereospecific installation of a quaternary center.
- Published
- 2007
- Full Text
- View/download PDF
12. Application of PatchXpress planar patch clamp technology to the screening of new drug candidates for cardiac KCNQ1/KCNE1 (I Ks) activity.
- Author
-
Trepakova ES, Malik MG, Imredy JP, Penniman JR, Dech SJ, and Salata JJ
- Subjects
- Animals, CHO Cells, Cell Line, Chemistry, Pharmaceutical, Cricetinae, Cricetulus, Data Interpretation, Statistical, Electrophysiology, Ether-A-Go-Go Potassium Channels drug effects, Guinea Pigs, Humans, In Vitro Techniques, Myocytes, Cardiac drug effects, Cardiovascular Agents pharmacology, Drug Evaluation, Preclinical instrumentation, KCNQ1 Potassium Channel drug effects, Patch-Clamp Techniques instrumentation, Potassium Channels, Voltage-Gated drug effects
- Abstract
A cardiac safety concern for QT prolongation and potential for pro-arrhythmia exists due to inhibition of the cardiac slowly activating delayed rectifier potassium current, I(Ks). Selective inhibitors of I Ks have been shown to prolong the QT interval in animal models. On the other hand, I Ks has been considered as a target for anti-arrhythmic therapy due to certain biophysical and pharmacological properties and its expression pattern in the heart. Consequently, we have developed a method utilizing a human embryonic kidney (HEK)-293 cell line expressing KCNQ1/KCNE1 (genes that encode for the I Ks channel) as a model for screening of new compounds for I Ks activity. This study was designed (1) to establish and optimize the experimental conditions for measurement of I Ks using PatchXpress() 7000A (Molecular Devices Corporation, Sunnyvale, CA) and (2) to test the effects of I Ks inhibitors and compare the 50% inhibitory concentration (IC50) values determined with PatchXpress versus conventional patch clamp in order to validate the PatchXpress approach for higher-throughput I Ks screening. Biophysical properties of HEK/I Ks recorded with PatchXpress were similar to those recorded with conventional patch-clamp and reported in the literature. The IC50 values for I Ks block determined with PatchXpress correlated well with conventional patch-clamp values from HEK-293 cells as well as from native cardiac myocytes for the majority of compounds tested. Electrophysiological recording of I Ks expressed in HEK-293 cells with the PatchXpress is of acceptable quality for screening purposes. This approach can be utilized for functional prescreening of development compounds for I Ks inhibition either for optimizing lead anti-arrhythmic or other therapeutic candidates or to exclude compounds with the potential to prolong QT.
- Published
- 2007
- Full Text
- View/download PDF
13. Kinesin spindle protein (KSP) inhibitors. Part 6: Design and synthesis of 3,5-diaryl-4,5-dihydropyrazole amides as potent inhibitors of the mitotic kinesin KSP.
- Author
-
Coleman PJ, Schreier JD, Cox CD, Fraley ME, Garbaccio RM, Buser CA, Walsh ES, Hamilton K, Lobell RB, Rickert K, Tao W, Diehl RE, South VJ, Davide JP, Kohl NE, Yan Y, Kuo L, Prueksaritanont T, Li C, Mahan EA, Fernandez-Metzler C, Salata JJ, and Hartman GD
- Subjects
- ATP Binding Cassette Transporter, Subfamily B, Member 1 antagonists & inhibitors, Antineoplastic Agents chemical synthesis, Antineoplastic Agents pharmacology, Cell Line, Tumor, Chemical Phenomena, Chemistry, Physical, Drug Design, Drug Resistance, Neoplasm, Genes, MDR drug effects, Humans, Indicators and Reagents, Solubility, Stereoisomerism, Structure-Activity Relationship, Amides chemical synthesis, Amides pharmacology, Antimitotic Agents chemical synthesis, Antimitotic Agents pharmacology, Kinesins antagonists & inhibitors, Mitosis drug effects, Pyrazoles chemical synthesis, Pyrazoles pharmacology
- Abstract
3,5-diaryl-4,5-dihydropyrazoles were discovered to be potent KSP inhibitors with excellent in vivo potency. These enzyme inhibitors possess desirable physical properties that can be readily modified by incorporation of a weakly basic amine. Careful adjustment of amine basicity was essential for preserving cellular potency in a multidrug resistant cell line while maintaining good aqueous solubility.
- Published
- 2007
- Full Text
- View/download PDF
14. Novel, potent inhibitors of human Kv1.5 K+ channels and ultrarapidly activating delayed rectifier potassium current.
- Author
-
Lagrutta A, Wang J, Fermini B, and Salata JJ
- Subjects
- Animals, Biphenyl Compounds chemistry, CHO Cells, Cricetinae, Cricetulus, Dose-Response Relationship, Drug, Guinea Pigs, Humans, Myocytes, Cardiac metabolism, Oocytes metabolism, Organophosphorus Compounds chemistry, Potassium Channel Blockers chemistry, Transfection, Xenopus laevis, Action Potentials drug effects, Biphenyl Compounds pharmacology, Kv1.5 Potassium Channel antagonists & inhibitors, Myocytes, Cardiac drug effects, Oocytes drug effects, Organophosphorus Compounds pharmacology, Potassium Channel Blockers pharmacology
- Abstract
We have identified a series of diphenyl phosphine oxide (DPO) compounds that are potent frequency-dependent inhibitors of cloned human Kv1.5 (hKv1.5) channels. DPO inhibited hKv1.5 expressed in Chinese hamster ovary cells in a concentration-dependent manner preferentially during channel activation and slowed the deactivating tail current, consistent with a predominant open-channel blocking mechanism. Varying kinetics of DPO interaction with Kv1.5 channels resulted in differing potencies and frequency dependencies of inhibition that were comparable for both expressed hKv1.5 current and native ultrarapidly activating delayed rectifier potassium current (IKur) in human atrial myocytes. Selectivity of DPO versus other cardiac K+ channels was demonstrated in human atrial myocytes (IKur versus transient outward potassium current) and guinea pig ventricular myocytes [IKur versus rapidly activating delayed rectifier potassium current (IKr), slowly activating delayed rectifier potassium current (IKs) and inward rectifier potassium current (IK1), and one compound (DPO-1) was shown to be 15-fold more selective for Kv1.5 versus Kv3.1 channels expressed in Xenopus oocytes. DPO-1 also prolonged action potentials of isolated human atrial but not ventricular myocytes, in contrast to the effect of a selective IKr blocker. The selectivity and kinetics of inhibition hKv1.5 and IKur by DPO and the resulting selective prolongation of atrial repolarization could provide an effective profile for treatment of supraventricular arrhythmias.
- Published
- 2006
- Full Text
- View/download PDF
15. Flunarizine is a highly potent inhibitor of cardiac hERG potassium current.
- Author
-
Trepakova ES, Dech SJ, and Salata JJ
- Subjects
- Animals, CHO Cells, Calcium Channel Blockers chemistry, Cell Culture Techniques, Cell Line, Cricetinae, Dose-Response Relationship, Drug, ERG1 Potassium Channel, Electrophysiologic Techniques, Cardiac, Ether-A-Go-Go Potassium Channels genetics, Ether-A-Go-Go Potassium Channels physiology, Flunarizine chemistry, Heart drug effects, Humans, Molecular Structure, Patch-Clamp Techniques, Potassium metabolism, Potassium Channels, Voltage-Gated genetics, Potassium Channels, Voltage-Gated physiology, Calcium Channel Blockers pharmacology, Ether-A-Go-Go Potassium Channels drug effects, Flunarizine pharmacology, Heart physiology, Potassium Channels, Voltage-Gated antagonists & inhibitors
- Abstract
Flunarizine has been widely used for the management of a variety of disorders such as peripheral vascular diseases, migraine, and epilepsy. The majority of its beneficial effects have been attributed to its ability to inhibit voltage-gated Ca2+ channels in the low micromolar range, albeit non-selectively, as flunarizine has been shown to inhibit a variety of ion channels. We examined the effects of flunarizine on potassium currents through cardiac channels encoded by the human ether-a-go-go related gene (hERG) stably expressed in CHO cells. In this study, we have characterized the effect of flunarizine on biophysical properties of hERG potassium currents with standard whole-cell voltage-clamp techniques. Notably, flunarizine is a highly potent inhibitor of hERG current with an IC50 value of 5.7 nM. The effect of flunarizine on hERG potassium current is concentration and time dependent, and displays voltage dependence over the voltage range between -40 and 0 mV. At concentrations near or above the IC50, flunarizine causes a negative shift in the voltage dependence of hERG current activation and accelerates tail current deactivation. Flunarizine preferentially blocks the activated state of the channel and displays weak frequency dependence of inhibition. Flunarizine also inhibits KCNQ1/KCNE1 channel current with an IC50 of 0.76 microM.
- Published
- 2006
- Full Text
- View/download PDF
16. Functional expression of L- and T-type Ca2+ channels in murine HL-1 cells.
- Author
-
Xia M, Salata JJ, Figueroa DJ, Lawlor AM, Liang HA, Liu Y, and Connolly TM
- Subjects
- Animals, Calcium pharmacology, Calcium Channels, L-Type genetics, Calcium Channels, T-Type genetics, Cell Line, Electric Conductivity, Heart Atria cytology, Ion Transport drug effects, Mibefradil pharmacology, Mice, Myocytes, Cardiac drug effects, Nimodipine pharmacology, Patch-Clamp Techniques, Pimozide pharmacology, Potassium pharmacology, Verapamil pharmacology, Calcium metabolism, Calcium Channels, L-Type metabolism, Calcium Channels, T-Type metabolism, Myocytes, Cardiac metabolism
- Abstract
In the search for a readily available source of native cardiac cells, we investigated the molecular and pharmacological properties of the immortalized cardiac atrial myocyte cell line, HL-1 cells. This work focused on the expression pattern of voltage-gated Ca2+ channels (VGCC). Reverse transcription-polymerase chain reaction analysis revealed that HL-1 cells have mRNA for several types of Ca2+ channels including the L-types, alpha1C and alpha1D, as well as T-types, alpha1H and alpha1G, but are lacking N-type, alpha1B and the T-type, alpha1I. Western blot analysis demonstrated significant alpha1C protein subunit expression, with less alpha1D subunit apparent, while alpha1A, alpha1B and alpha1E subunit expression was undetectable. Immunocytochemical staining showed that the alpha1C protein subunit is expressed predominantly on the cell surface, whereas the alpha1D protein is expressed mostly intracellularly. Whole-cell patch-clamp measurements demonstrated the presence of low (ICa,T) and high (ICa,L) voltage-activated Ca2+ currents, with preferential sensitivity to mibefradil and nimodipine, respectively. Addition of increasing external Ca2+ concentrations, [Ca2+]o, resulted in Ca2+ influx measured by fluorometric imaging with an EC50 of 0.8 mM [Ca2+]o. At a fixed [Ca2+]o of 0.125 mM, Ca2+ influx was also triggered by increasing the extracellular K+ concentration, [K+]o, with an EC50 of 3.7 mM [K+]o. As increasing [K+]o depolarizes the cell, this latter result is consistent with Ca2+ influx through a voltage-dependent mechanism. L-type (nimodipine and verapamil) and T-type (mibefradil and pimozide) Ca2+ channel blockers inhibited Ca2+ influx with IC50s of 1, 2, 0.4 and 0.2 microM, respectively. Antagonists of N-type (omega-conotoxins GVIA) and P/Q-type (MVIIC or omega-agatoxin IVA) did not inhibit Ca2+ influx, consistent with the lack of expression of N-, P-, or Q-type channels observed in the molecular studies. Taken together, these findings indicate that HL-1 cells express L- and T-subtypes of VGCC and are a unique in vitro model system for the study of native, mammalian cardiac Ca2+ channels.
- Published
- 2004
- Full Text
- View/download PDF
17. In vivo canine cardiac electrophysiologic profile of 1,4-benzodiazepine IKs blockers.
- Author
-
Stump GL, Smith GR, Tebben AJ, Jahansouz H, Salata JJ, Selnick HG, Claremon DA, and Lynch JJ Jr
- Subjects
- Animals, Atrioventricular Node drug effects, Benzodiazepines chemistry, Bundle of His drug effects, Dogs, Electrocardiography, Electrophysiologic Techniques, Cardiac, Female, Heart Rate drug effects, Injections, Intravenous, Male, Molecular Structure, Potassium Channel Blockers chemistry, Action Potentials drug effects, Benzodiazepines pharmacology, Heart Conduction System drug effects, Potassium Channel Blockers pharmacology
- Abstract
Previous cardiac electrophysiologic studies of blockers of the slowly activating delayed rectifier (IKs) current have focused primarily on ventricular repolarization. This report summarizes an extensive in vivo cardiac electrophysiologic profile of four 1,4-benzodiazepine IKs blocker analogues (L-761334, L-763540, L-761710, and L-768673) in dogs. At 3.0 mg/kg intravenously, all four analogues elicited 14.5%-21.4% increases in ventricular refractoriness and 19.2%-22.6% increases in QTc interval. Concomitant 11.1%-13.5% increases in atrial refractoriness were noted with all four analogues. Decreases in sinus heart rate of 8.4%-17.3% were noted with all four compounds. No effects on atrial, His Purkinje, ventricular conduction or atrial and ventricular excitation were observed. One analogue, L-761710, significantly delayed atrioventricular (AV) nodal conduction (40.7+/-17.4% increase in atrial-to-His interval) and increased the AV conduction system functional refractory period 19.9+/-6.2%. The lack of effect of the other three 1,4-benzodiazepine IKs blockers on AV nodal function at dosages producing comparable effects on atrial and ventricular refractoriness suggest that the AV nodal effects of L-761710 were unrelated to IKs blockade. These findings indicate IKs plays important roles in both atrial and ventricular refractoriness as well as pacemaker function in the dog heart, suggesting potential utility for IKs blockers in the treatment of atrial and ventricular arrhythmias.
- Published
- 2003
- Full Text
- View/download PDF
18. Saxitoxin is a gating modifier of HERG K+ channels.
- Author
-
Wang J, Salata JJ, and Bennett PB
- Subjects
- Cell Line, ERG1 Potassium Channel, Ether-A-Go-Go Potassium Channels, Gene Expression Regulation, Heart physiology, Humans, Kinetics, Long QT Syndrome physiopathology, Membrane Potentials physiology, Transcriptional Regulator ERG, Cation Transport Proteins, DNA-Binding Proteins, Models, Theoretical, Potassium Channels drug effects, Potassium Channels physiology, Potassium Channels, Voltage-Gated, Saxitoxin pharmacology, Trans-Activators
- Abstract
Potassium (K+) channels mediate numerous electrical events in excitable cells, including cellular membrane potential repolarization. The hERG K+ channel plays an important role in myocardial repolarization, and inhibition of these K+ channels is associated with long QT syndromes that can cause fatal cardiac arrhythmias. In this study, we identify saxitoxin (STX) as a hERG channel modifier and investigate the mechanism using heterologous expression of the recombinant channel in HEK293 cells. In the presence of STX, channels opened slower during strong depolarizations, and they closed much faster upon repolarization, suggesting that toxin-bound channels can still open but are modified, and that STX does not simply block the ion conduction pore. STX decreased hERG K+ currents by stabilizing closed channel states visualized as shifts in the voltage dependence of channel opening to more depolarized membrane potentials. The concentration dependence for steady-state modification as well as the kinetics of onset and recovery indicate that multiple STX molecules bind to the channel. Rapid application of STX revealed an apparent "agonist-like" effect in which K+ currents were transiently increased. The mechanism of this effect was found to be an effect on the channel voltage-inactivation relationship. Because the kinetics of inactivation are rapid relative to activation for this channel, the increase in K+ current appeared quickly and could be subverted by a decrease in K+ currents due to the shift in the voltage-activation relationship at some membrane potentials. The results are consistent with a simple model in which STX binds to the hERG K+ channel at multiple sites and alters the energetics of channel gating by shifting both the voltage-inactivation and voltage-activation processes. The results suggest a novel extracellular mechanism for pharmacological manipulation of this channel through allosteric coupling to channel gating.
- Published
- 2003
- Full Text
- View/download PDF
19. Novel 5-cyclopropyl-1,4-benzodiazepin-2-ones as potent and selective I(Ks)-blocking class III antiarrhythmic agents.
- Author
-
Butcher JW, Liverton NJ, Claremon DA, Freidinger RM, Jurkiewicz NK, Lynch JJ, Salata JJ, Wang J, Dieckhaus CM, Slaughter DE, and Vyas K
- Subjects
- Animals, Anti-Arrhythmia Agents metabolism, Benzodiazepines metabolism, Delayed Rectifier Potassium Channels, Dogs, Dose-Response Relationship, Drug, Guinea Pigs, Heart Rate drug effects, Hemodynamics drug effects, Humans, In Vitro Techniques, Microsomes, Liver metabolism, Patch-Clamp Techniques, Potassium Channel Blockers metabolism, Refractory Period, Electrophysiological drug effects, Structure-Activity Relationship, Anti-Arrhythmia Agents chemical synthesis, Anti-Arrhythmia Agents pharmacology, Benzodiazepines chemical synthesis, Benzodiazepines pharmacology, Potassium Channel Blockers chemical synthesis, Potassium Channel Blockers pharmacology, Potassium Channels drug effects, Potassium Channels, Voltage-Gated
- Abstract
Novel 5-cyclopropyl-1,4-benzodiazepin-2-ones having various N-l substituents were identified as potent and selective blockers of the slowly activating cardiac delayed rectifier potassium current (I(Ks)). Compound 11 is the most potent I(Ks) channel blocker reported to date.
- Published
- 2003
- Full Text
- View/download PDF
20. Functional and pharmacological properties of canine ERG potassium channels.
- Author
-
Wang J, Della Penna K, Wang H, Karczewski J, Connolly TM, Koblan KS, Bennett PB, and Salata JJ
- Subjects
- Animals, Benzopyrans metabolism, Benzopyrans pharmacology, Binding, Competitive, Blotting, Western, Cell Line, ERG1 Potassium Channel, Electric Conductivity, Ether-A-Go-Go Potassium Channels, Humans, Immunologic Techniques, Ion Channel Gating, Kinetics, Patch-Clamp Techniques, Piperidines metabolism, Piperidines pharmacology, Potassium metabolism, Staining and Labeling, Temperature, Dogs physiology, Potassium Channel Blockers pharmacology, Potassium Channels drug effects, Potassium Channels physiology, Potassium Channels, Voltage-Gated
- Abstract
We established HEK-293 cell lines that stably express functional canine ether-à-go-go-related gene (cERG) K(+) channels and examined their biophysical and pharmacological properties with whole cell patch clamp and (35)S-labeled MK-499 ([(35)S]MK-499) binding displacement. Functionally, cERG current had the hallmarks of cardiac delayed rectifier K(+) current (I(Kr)). Channel opening was time- and voltage dependent with threshold near -40 mV. The half-maximum activation voltage was -7.8 +/- 2.4 mV at 23 degrees C, shifting to -31.9 +/- 1.2 mV at 36 degrees C. Channels activated with a time constant of 13 +/- 1 ms at +20 mV, showed prominent inward rectification at depolarized potentials, were highly K(+) selective (Na(+)-to-K(+) permeability ratio = 0.007), and were potently inhibited by I(Kr) blockers. Astemizole, terfenadine, cisapride, and MK-499 inhibited cERG and human ERG (hERG) currents with IC(50) values of 1.3, 13, 19, and 15 nM and 1.2, 9, 14, and 21 nM, respectively, and competitively displaced [(35)S]MK-499 binding from cERG and hERG with IC(50) values of 0.4, 12, 35, and 0.6 nM and 0.8, 5, 47, and 0.7 nM, respectively. cERG channels had biophysical properties appropriate for canine action potential repolarization and were pharmacologically sensitive to agents known to prolong QT. A novel MK-499 binding assay provides a new tool to detect agents affecting ERG channels.
- Published
- 2003
- Full Text
- View/download PDF
21. Increasing I(Ks) corrects abnormal repolarization in rabbit models of acquired LQT2 and ventricular hypertrophy.
- Author
-
Xu X, Salata JJ, Wang J, Wu Y, Yan GX, Liu T, Marinchak RA, and Kowey PR
- Subjects
- Action Potentials drug effects, Animals, Benzodiazepines pharmacology, Delayed Rectifier Potassium Channels, Electrophysiology, Long QT Syndrome classification, Male, Potassium Channels drug effects, Rabbits, Reaction Time drug effects, Hypertrophy, Left Ventricular physiopathology, Long QT Syndrome physiopathology, Potassium Channels metabolism, Potassium Channels, Voltage-Gated
- Abstract
Excessive action potential (AP) prolongation and early afterdepolarizations (EAD) are triggers of malignant ventricular arrhythmias. A slowly activating delayed rectifier K+ current (I(Ks)) is important for repolarization of ventricular AP. We examined the effects of I(Ks) activation by a new benzodiazepine (L3) on the AP of control, dofetilide-treated, and hypertrophied rabbit ventricular myocytes. In both control and hypertrophied myocytes, L3 activated I(Ks) via a negative shift in the voltage dependence of activation and a slowing of deactivation. L3 had no effect on L-type Ca(2+) current or other cardiac K+ currents tested. L3 shortened AP of control, dofetilide-treated, and hypertrophied myocytes more at 0.5 than 2 Hz. Selective activation of I(Ks) by L3 attenuates prolonged AP and eliminated EAD induced by rapidly activating delayed rectifier K+ current inhibition in control myocytes at 0.5 Hz and spontaneous EAD in hypertrophied myocytes at 0.2 Hz. Pharmacological activation of I(Ks) is a promising new strategy to suppress arrhythmias resulting from excessive AP prolongation in patients with certain forms of long QT syndrome or cardiac hypertrophy and failure.
- Published
- 2002
- Full Text
- View/download PDF
22. Antiarrhythmic efficacy of combined I(Ks) and beta-adrenergic receptor blockade.
- Author
-
Lynch JJ Jr, Salata JJ, Wallace AA, Stump GL, Gilberto DB, Jahansouz H, Liverton NJ, Selnick HG, and Claremon DA
- Subjects
- Adrenergic beta-Agonists pharmacology, Animals, Dogs, Electric Stimulation, Electrophysiology, Female, Heart drug effects, Heart Rate drug effects, Heart Ventricles drug effects, In Vitro Techniques, Isoproterenol pharmacology, Male, Myocardial Infarction pathology, Myocardial Ischemia pathology, Timolol pharmacology, Ventricular Function, Acetamides pharmacology, Adrenergic beta-Antagonists pharmacology, Anti-Arrhythmia Agents, Benzodiazepinones pharmacology, Potassium Channel Blockers
- Abstract
Suppression of malignant ventricular arrhythmias by selective blockade of the cardiac slowly activating delayed rectifier current (I(Ks)) has been demonstrated with the benzodiazepine L-768673 [(R)-2-(2,4-trifluoromethyl-phenyl)-N-[2-oxo-5-phenyl-1-(2,2,2-trifluoro-ethyl)-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl]acetamide] in canine models of recent and healed myocardial infarction. The present study extends the initial antiarrhythmic assessment of I(Ks) blockade by demonstrating prevention of ischemic malignant arrhythmias in dogs with recent (8.0 +/- 0.4 days) anterior myocardial infarction with the coadministration of a subeffective dose of L-768673 and a subeffective, minimally beta-adrenergic blocking dose of timolol. Administered individually, neither 0.3 microg/kg i.v. L-768673 nor 1.0 microg/kg i.v. timolol prevented the induction of ventricular tachyarrhythmia (VT) by programmed ventricular stimulation (PVS) or the development of malignant ventricular arrhythmia in response to acute coronary artery thrombosis. In contrast, coadministration of 0.3 microg/kg i.v. L-768673 + 1.0 microg/kg i.v. timolol suppressed the induction of VT by PVS (8/10, 80% rendered noninducible versus 1/10, 10% noninducible in vehicle group; p < 0.01) and prevented the development of acute ischemic lethal arrhythmias (3/10, 30% incidence versus 8/10, 80% incidence in vehicle group; p < 0.05). Concomitant administration of low-dose L-768673 + timolol produced modest increases in QTc and paced QT intervals (4.5 +/- 1.2 and 5.5 +/- 1.4%; both p < 0.01), increases in noninfarct zone relative and effective refractory periods (7.0 +/- 1.7 and 12.3 +/- 3.0%; both p < 0.01), and lesser increases in infarct zone relative and effective refractory periods (5.3 +/- 1.6 and 5.8 +/- 1.4%; both p < 0.01). These findings suggest that concomitant low-dose I(Ks) and beta-adrenergic blockade may constitute a potential pharmacologic strategy for prevention of malignant ischemic ventricular arrhythmias.
- Published
- 2002
- Full Text
- View/download PDF
23. Left ventricular hypertrophy decreases slowly but not rapidly activating delayed rectifier potassium currents of epicardial and endocardial myocytes in rabbits.
- Author
-
Xu X, Rials SJ, Wu Y, Salata JJ, Liu T, Bharucha DB, Marinchak RA, and Kowey PR
- Subjects
- Animals, Delayed Rectifier Potassium Channels, Electrophysiology, Male, Myocardium metabolism, Rabbits, Action Potentials physiology, Endocardium physiopathology, Hypertrophy, Left Ventricular physiopathology, Pericardium physiopathology, Potassium Channels metabolism, Potassium Channels, Voltage-Gated
- Abstract
Background: Delayed rectifier K(+) currents are critical to action potential (AP) repolarization. The present study examines the effects of left ventricular hypertrophy (LVH) on delayed rectifier K(+) currents and their contribution to AP repolarization in both epicardial (Epi) and endocardial (Endo) myocytes., Methods and Results: VH was induced in rabbits by a 1-kidney removal, 1-kidney vascular clamping method. Slowly (I(Ks)) and rapidly (I(Kr)) activating delayed rectifier K(+) currents were recorded by the whole-cell patch-clamp technique, and APs were recorded by the microelectrode technique. In normal rabbit left ventricular myocytes, I(Ks) densities were larger in Epi than in Endo (1.1+/-0.1 versus 0.43+/-0.07 pA/pF), whereas I(Kr) density was similar between Epi and Endo (0.31+/-0.05 versus 0.36+/-0.07 pA/pF) at 20 mV. LVH reduced I(Ks) density to a similar extent (approximately 40%) in both Epi and Endo but had no significant effect on I(Kr) in either Epi or Endo. Consequently, I(Kr) was expected to contribute more to AP repolarization in LVH than in control. This was confirmed by specific I(Kr) block with dofetilide, which prolonged AP significantly more in LVH than in control (31+/-3% versus 18+/-2% in Epi; 53+/-6% versus 32+/-4% in Endo at 2 Hz). In contrast, L-768,673 (a specific I(Ks) blocker) prolonged AP less in LVH than in control. The very small I(Ks) density in Endo with LVH is consistent with the greater incidence of early afterdepolarizations induced in this region by dofetilide., Conclusions: LVH induces a decrease in I(Ks) density and increases the propensity to develop early afterdepolarizations, especially in Endo.
- Published
- 2001
- Full Text
- View/download PDF
24. Synthesis and class III type antiarrhythmic activity of 4-aroyl (and aryl)-l-aralkylpiperazines.
- Author
-
Kanojia RM, Salata JJ, and Kauffman J
- Subjects
- Animals, Anti-Arrhythmia Agents pharmacology, Biological Assay, Ferrets, In Vitro Techniques, Isometric Contraction drug effects, Male, Papillary Muscles drug effects, Papillary Muscles physiology, Piperazines chemical synthesis, Piperidines chemical synthesis, Piperidines pharmacology, Structure-Activity Relationship, Anti-Arrhythmia Agents chemical synthesis, Piperazines pharmacology
- Abstract
The synthesis and in vitro Class III antiarrhythmic activity of several 4-aroyl (and aryl)-1-aralkylpiperazine and piperidine derivatives are described. Among several potent compounds identified in the series, RWJ-28810 (3), with its EC20 of 3 nM, ranks as one of the most potent (in vitro) compounds reported.
- Published
- 2000
- Full Text
- View/download PDF
25. Modification of cardiac Na(+) current by RWJ 24517 and its enantiomers in guinea pig ventricular myocytes.
- Author
-
Tsushima RG, Kelly JE, Salata JJ, Liberty KN, and Wasserstrom JA
- Subjects
- Animals, Dose-Response Relationship, Drug, Guinea Pigs, In Vitro Techniques, Mercaptopurine pharmacology, Muscle Contraction drug effects, Patch-Clamp Techniques, Potassium metabolism, Sodium metabolism, Stereoisomerism, Time Factors, Action Potentials drug effects, Cardiotonic Agents pharmacology, Heart Ventricles drug effects, Mercaptopurine analogs & derivatives, Piperazines pharmacology
- Abstract
We examined the effects of the cardiotonic agent RWJ 24517 (Carsatrin, racemate) and its (S)- and (R)-enantiomers on action potential duration, Na(+) current (I(Na)), and delayed rectifier K(+) current (I(K)) of guinea pig ventricular myocytes. RWJ 24517 (0. 1 and 1 microM) prolongation of action potential duration could not be accounted for by suppression of either the rapid (I(Kr)) or slow (I(Ks),) component of I(K), although RWJ 24517 did reduce I(Kr) at concentrations of 1 microM. A more dramatic effect of RWJ 24517 (0.1-1 microM) and the (S)-enantiomer of RWJ 24517 (0.1-3 microM) was an increase in peak I(Na) and slowing of the rate of I(Na) decay, eliciting a large steady-state current. Neither RWJ 24517 nor the (S)-enantiomer affected the fast time constant for I(Na) decay, but both significantly increased the slow time constant, in addition to increasing the proportion of I(Na) decaying at the slow rate. Both agents elicited a use-dependent decrease of peak I(Na) (3-10 microM), which probably resulted from a slowing of both fast and slow rates of recovery from inactivation. In contrast, the (R)-enantiomer of RWJ 24517 did not induce a steady-state component I(Na) or increase peak I(Na) up to 10 microM, but it decreased peak I(Na) at 30 microM. The (R)-enantiomer displayed little use-dependent reduction of I(Na) during trains of repetitive pulses and had no effect on rates of inactivation or recovery from inactivation. These actions of the racemate and the (S)-stereoisomer to slow inactivation and to prolong both Na(+) influx and action potential duration may contribute to the positive inotropic actions of these agents because the resulting accumulation of intracellular Na(+) would increase intracellular Ca(2+) via Na(+)/Ca(2+) exchange.
- Published
- 1999
26. A novel benzodiazepine that activates cardiac slow delayed rectifier K+ currents.
- Author
-
Salata JJ, Jurkiewicz NK, Wang J, Evans BE, Orme HT, and Sanguinetti MC
- Subjects
- Action Potentials drug effects, Animals, Delayed Rectifier Potassium Channels, Guinea Pigs, Heart physiology, Heart Ventricles drug effects, Humans, Ion Channels drug effects, KCNQ Potassium Channels, KCNQ1 Potassium Channel, Potassium Channels metabolism, Receptors, Adrenergic, beta drug effects, Receptors, Adrenergic, beta metabolism, Ventricular Function, Xenopus laevis genetics, Benzodiazepines pharmacology, Heart drug effects, Potassium Channels drug effects, Potassium Channels, Voltage-Gated
- Abstract
The slowly activating delayed rectifier K+ current, IKs, is an important modulator of cardiac action potential repolarization. Here, we describe a novel benzodiazepine, [L-364,373 [(3-R)-1, 3-dihydro-5-(2-fluorophenyl)-3-(1H-indol-3-ylmethyl)-1-methyl-2H- 1,4-benzodiazepin-2-one] (R-L3), that activates IKs and shortens action potentials in guinea pig cardiac myocytes. These effects were additive to isoproterenol, indicating that channel activation by R-L3 was independent of beta-adrenergic receptor stimulation. The increase of IKs by R-L3 was stereospecific; the S-enantiomer, S-L3, blocked IKs at all concentrations examined. The increase in IKs by R-L3 was greatest at voltages near the threshold for normal channel activation, caused by a shift in the voltage dependence of IKs activation. R-L3 slowed the rate of IKs deactivation and shifted the half-point of the isochronal (7.5 sec) activation curve for IKs by -16 mV at 0.1 microM and -24 mV at 1 microM. R-L3 had similar effects on cloned KvLQT1 channels expressed in Xenopus laevis oocytes but did not affect channels formed by coassembly of KvLQT1 and hminK subunits. These findings indicate that the association of minK with KvLQT1 interferes with the binding of R-L3 or prevents its action once bound to KvLQT1 subunits.
- Published
- 1998
- Full Text
- View/download PDF
27. Blockade of HERG channels by the class III antiarrhythmic azimilide: mode of action.
- Author
-
Busch AE, Eigenberger B, Jurkiewicz NK, Salata JJ, Pica A, Suessbrich H, and Lang F
- Subjects
- Animals, Cell Line, ERG1 Potassium Channel, Electric Stimulation, Ether-A-Go-Go Potassium Channels, Guinea Pigs, Hydantoins, Membrane Potentials physiology, Oocytes drug effects, Oocytes metabolism, Patch-Clamp Techniques, Potassium pharmacology, Potassium Channels metabolism, RNA, Messenger biosynthesis, Xenopus, Anti-Arrhythmia Agents pharmacology, Cation Transport Proteins, DNA-Binding Proteins, Imidazoles pharmacology, Imidazolidines, Piperazines pharmacology, Potassium Channel Blockers, Potassium Channels, Voltage-Gated, Trans-Activators
- Abstract
1. The class III antiarrhythmic azimilide has previously been shown to inhibit I(Ks) and I(Kr) in guinea-pig cardiac myocytes and I(Ks) (minK) channels expressed in Xenopus oocytes. Because HERG channels underly the conductance I(Kr), in human heart, the effects of azimilide on HERG channels expressed in Xenopus oocytes were the focus of the present study. 2. In contrast to other well characterized HERG channel blockers, azimilide blockade was reverse use-dependent, i.e., the relative block and apparent affinity of azimilide decreased with an increase in channel activation frequency. Azimilide blocked HERG channels at 0.1 and 1 Hz with IC50s of 1.4 microM and 5.2 microM respectively. 3. In an envelope of tail test, HERG channel blockade increased with increasing channel activation, indicating binding of azimilide to open channels. 4. Azimilide blockade of HERG channels expressed in Xenopus oocytes and I(Kr) in mouse AT-1 cells was decreased under conditions of high [K+]e, whereas block of slowly activating I(Ks) channels was not affected by changes in [K+]e. 5. In summary, azimilide is a blocker of cardiac delayed rectifier channels, I(Ks) and HERG. Because of the distinct effects of stimulation frequency and [K+]e on azimilide block of I(Kr) and I(Ks) channels, we conclude that the relative contribution of block of each of these cardiac delayed rectifier channels depends on heart frequency. [K+]e and regulatory status of the respective channels.
- Published
- 1998
- Full Text
- View/download PDF
28. Class III antiarrhythmic activity in vivo by selective blockade of the slowly activating cardiac delayed rectifier potassium current IKs by (R)-2-(2,4-trifluoromethyl)-N-[2-oxo-5-phenyl-1-(2,2,2-trifluoroethyl)- 2, 3-dihydro-1H-benzo[e][1,4]diazepin-3-yl]acetamide.
- Author
-
Selnick HG, Liverton NJ, Baldwin JJ, Butcher JW, Claremon DA, Elliott JM, Freidinger RM, King SA, Libby BE, McIntyre CJ, Pribush DA, Remy DC, Smith GR, Tebben AJ, Jurkiewicz NK, Lynch JJ, Salata JJ, Sanguinetti MC, Siegl PK, Slaughter DE, and Vyas K
- Subjects
- Administration, Oral, Animals, Cells, Cultured, Dogs, Electrocardiography, Ambulatory drug effects, Guinea Pigs, Heart physiology, Humans, Myocardium cytology, Potassium Channels physiology, Xenopus, Acetamides chemical synthesis, Acetamides pharmacology, Anti-Arrhythmia Agents chemical synthesis, Anti-Arrhythmia Agents pharmacology, Benzodiazepinones chemical synthesis, Benzodiazepinones pharmacology, Heart drug effects, Potassium Channel Blockers
- Published
- 1997
- Full Text
- View/download PDF
29. IK of rabbit ventricle is composed of two currents: evidence for IKs.
- Author
-
Salata JJ, Jurkiewicz NK, Jow B, Folander K, Guinosso PJ Jr, Raynor B, Swanson R, and Fermini B
- Subjects
- Adrenergic beta-Agonists pharmacology, Amino Acid Sequence, Animals, Anti-Arrhythmia Agents pharmacology, Electric Conductivity, Electrophysiology, Gene Expression, Guinea Pigs, Heart physiology, Humans, Hydantoins, Imidazoles pharmacology, Isoproterenol pharmacology, Mice, Molecular Sequence Data, Mutation, Oocytes metabolism, Piperazines pharmacology, Potassium Channels genetics, Rabbits, Rats, Xenopus laevis, Imidazolidines, Potassium Channels physiology, Ventricular Function
- Abstract
The delayed rectifier K+ current (IK) in rabbit heart has long been thought to consist of only a single, rapidly activating, dofetilide-sensitive current, IKr. However, we find that IK of rabbit ventricular myocytes actually consists of both rapid and slow components, IKr and IKs, respectively, that can be isolated pharmacologically. Thus, after complete blockade of IKr with dofetilide, the remaining current, IKs, is homogeneous as judged by an envelope of tails test. IKs activates and deactivates slowly, continues to activate during sustained depolarizations, has a half-activation potential of 7.0 +/- 0.8 mV and slope factor of 11.0 +/- 0.7 mV, reverses at -77.2 +/- 1.3 mV (extracellular K+ concentration = 4 mM), is increased by removing extracellular K+, and is enhanced by isoproterenol and stocked by azimilide. Northern analysis demonstrates that the minK (IsK) gene, which encodes a subunit of the channel that underlies the IKs current, is expressed in rabbit heart. Expression of the rabbit protein in Xenopus oocytes elicits a slowly activating, voltage-dependent current, IsK, similar to those expressed previously from mouse, rat, guinea pig, and human genes. The results demonstrate that IKs is present in rabbit ventricle and therefore contributes to cardiac repolarization in this species.
- Published
- 1996
- Full Text
- View/download PDF
30. Mechanism of action potential prolongation by RP 58866 and its active enantiomer, terikalant. Block of the rapidly activating delayed rectifier K+ current, IKr.
- Author
-
Jurkiewicz NK, Wang J, Fermini B, Sanguinetti MC, and Salata JJ
- Subjects
- Action Potentials, Animals, ERG1 Potassium Channel, Electric Conductivity, Ether-A-Go-Go Potassium Channels, Guinea Pigs, Mice, Myocardium cytology, Oocytes metabolism, Osmolar Concentration, Patch-Clamp Techniques, Potassium physiology, Potassium Channels physiology, Reaction Time drug effects, Stereoisomerism, Xenopus, Anti-Arrhythmia Agents pharmacology, Cation Transport Proteins, Chromans pharmacology, DNA-Binding Proteins, Heart drug effects, Heart physiology, Piperidines pharmacology, Potassium antagonists & inhibitors, Potassium Channels, Voltage-Gated, Trans-Activators
- Abstract
Background: The class III antiarrhythmic agent RP 58866 and its active enantiomer, terikalant, are reported to selectively block the inward rectifier K+ current, IK1. These drugs have demonstrated efficacy in animal models of cardiac arrhythmias, suggesting that block of IK1 may be a useful antiarrhythmic mechanism. The symmetrical action potential (AP)-prolonging and bradycardic effects of these drugs, however, are inconsistent with a sole effect on IK1., Methods and Results: We studied the effects of RP 58866 and terikalant on AP and outward K+ currents in guinea pig ventricular myocytes. RP 58866 and terikalant potently blocked the rapidly activating delayed rectifier K+ current, IKr, with IC50S of 22 and 31 nmol/L, respectively. Block of IK1 was approximately 250-fold less potent; IC50S were 8 and 6 mumol/L, respectively. No significant block of the slowly activating delayed rectifier, IK1, was observed at < or = 10 mumol/L. The phenotypical IKr currents in mouse AT-1 cells and Xenopus oocytes expressing HERG were also blocked 50% by 200 to 250 nmol/L RP 58866 or terikalant, providing further conclusive evidence for potent block of IKr. RP 58866 < or = 1 mumol/L and dofetilide increased AP duration symmetrically, consistent with selective block of IKr. Only higher concentrations (> or = 10 mumol/L) of RP 58866 slowed the rate of AP repolarization and decreased resting membrane potential, consistent with an additional but substantially less potent block of IK1., Conclusions: These data demonstrate that RP 58866 and terikalant are potent blockers of IKr and prompt a reinterpretation of previous studies that assumed specific block of IK1 by these drugs.
- Published
- 1996
- Full Text
- View/download PDF
31. Use-dependent effects of the class III antiarrhythmic agent NE-10064 (azimilide) on cardiac repolarization: block of delayed rectifier potassium and L-type calcium currents.
- Author
-
Fermini B, Jurkiewicz NK, Jow B, Guinosso PJ Jr, Baskin EP, Lynch JJ Jr, and Salata JJ
- Subjects
- Action Potentials drug effects, Animals, Calcium metabolism, Dose-Response Relationship, Drug, Ferrets, Guinea Pigs, Heart physiology, Hydantoins, In Vitro Techniques, Male, Refractory Period, Electrophysiological drug effects, Anti-Arrhythmia Agents pharmacology, Calcium Channel Blockers pharmacology, Heart drug effects, Imidazoles pharmacology, Imidazolidines, Piperazines pharmacology, Potassium Channel Blockers
- Abstract
We studied the effects of NE-10064 (azimilide), a new antiarrhythmic agent reported to be a selective blocker of the slowly activating component of the delayed rectifier, IKs. In ferret papillary muscles, NE-10064 increased effective refractory period (ERP) and decreased isometric twitch tension in a concentration-dependent manner (0.3-30 microM). Increases in ERP showed reverse use-dependence, and were greater at 1 than at 3 Hz. In contrast, changes in tension were use dependent, with larger decreases observed at 3 than at 1 Hz. In guinea pig ventricular myocytes, NE-10064 (0.3-3 microM) significantly prolonged action potential duration (APD) at 1 Hz. At 3 Hz, NE-10064 (0.3-1 microM) increased APD only slightly, and at 10 microM decreased APD and the plateau potential. NE-10064 potently blocked the rapidly activating component of the delayed rectifier, IKr (IC50 0.4 microM), and inhibited IKs (IC50 3 microM) with nearly 10-fold less potency. NE-10064 (10 microM) did not block the inward rectifier potassium current (IKl). NE-10064 (10 microM) blocked the L-type calcium current (ICa) in a use-dependent manner; block was greater at 3 than at 1 Hz. We conclude that (a) NE-10064's block of potassium currents is relatively selective for IKr over IKs, (b) NE-10064 inhibits ICa in a use-dependent fashion, and (c) NE-10064's effects on ERP and tension in papillary muscle as well as APD and action potential plateau level in myocytes may be explained by its potassium and calcium channel blocking properties.
- Published
- 1995
- Full Text
- View/download PDF
32. Comparison of binding to rapidly activating delayed rectifier K+ channel, IKr, and effects on myocardial refractoriness for class III antiarrhythmic agents.
- Author
-
Lynch JJ Jr, Baskin EP, Nutt EM, Guinosso PJ Jr, Hamill T, Salata JJ, and Woods CM
- Subjects
- Animals, Anti-Arrhythmia Agents metabolism, Binding, Competitive drug effects, Chromans metabolism, Chromans pharmacology, Electrophysiology, Guinea Pigs, Heart Ventricles cytology, Heart Ventricles drug effects, Heart Ventricles metabolism, Papillary Muscles drug effects, Papillary Muscles metabolism, Phenethylamines metabolism, Phenethylamines pharmacology, Piperidines metabolism, Piperidines pharmacology, Potassium Channels metabolism, Procainamide analogs & derivatives, Procainamide metabolism, Procainamide pharmacology, Pyridines metabolism, Pyridines pharmacology, Sotalol metabolism, Sotalol pharmacology, Structure-Activity Relationship, Sulfonamides metabolism, Sulfonamides pharmacology, Tritium metabolism, Anti-Arrhythmia Agents pharmacology, Potassium Channel Blockers
- Abstract
Saturation binding studies in guinea pig ventricular myocytes with 3H-dofetilide, a radioligand for the cardiac rapidly activating delayed rectifier K+ IKr channel, indicated specific high-affinity binding with a Kd of 83 nM and a Bmax of 0.18 pmol/mg cellular protein (1.36 x 10(6) sites/cell). Using displacement of high-affinity 3H-dofetilide binding as a measure of interaction with the IKr channel, potencies (Ki values) for binding to the IKr channel in guinea pig myocytes for six class III antiarrhythmic agents were characterized and compared to indices of functional electrophysiologic activity in isolated guinea pig papillary muscles [EC25 values, concentration required to increase effective refractory period (ERP) 25% above baseline]. Dofetilide, E-4031, sematilide, and d-sotalol, which have been characterized previously as selective IKr blockers, displayed good agreement between Ki values for displacement of 3H-dofetilide binding (47 +/- 7 nM, 38 +/- 8 nM, 12 +/- 5 microM, and approximately 100 microM, respectively) and EC25 values for increasing ERP in papillary muscles (45.0 nM, 76.9 nM, 20.2 microM and 63.5 microM, respectively). Ibutilide and RP58866, which have been reported to act via mechanisms other than IKr block, had Ki values for displacement of 3H-dofetilide binding (16 +/- 7 nM and 17 +/- 2 nM, respectively) that were approximately 10-fold lower than EC25 values for increasing ERP in papillary muscles (185.8 nM and 223.5 nM, respectively). The potent displacement of high-affinity 3H-dofetilide binding by ibutilide and RP58866 strongly suggest a role for interaction with IKr in their actions.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1995
- Full Text
- View/download PDF
33. Cardiac electrophysiological actions of the histamine H1-receptor antagonists astemizole and terfenadine compared with chlorpheniramine and pyrilamine.
- Author
-
Salata JJ, Jurkiewicz NK, Wallace AA, Stupienski RF 3rd, Guinosso PJ Jr, and Lynch JJ Jr
- Subjects
- Action Potentials drug effects, Animals, Dose-Response Relationship, Drug, Electrocardiography, Guinea Pigs, Heart physiology, In Vitro Techniques, Potassium Channels drug effects, Refractory Period, Electrophysiological drug effects, Astemizole pharmacology, Chlorpheniramine pharmacology, Heart drug effects, Pyrilamine pharmacology, Terfenadine pharmacology
- Abstract
We compared the cardiac electrophysiological actions of two types of H1-receptor antagonists--the piperidines, astemizole and terfenadine, and the nonpiperidines, chlorpheniramine and pyrilamine-in vitro in guinea pig ventricular myocytes and in vivo in chloralose-anesthetized dogs. Astemizole and terfenadine significantly increased action potential duration of guinea pig myocytes. This concentration-dependent prolongation of action potential duration was reverse frequency dependent and led to development of early afterdepolarizations, which occurred more frequently at higher concentrations and slower pacing frequencies. Astemizole and terfenadine potently blocked the rapidly activating component of the delayed rectifier, IKr, with IC50 values of 1.5 and 50 nmol/L, respectively. At 10 mumol/L, terfenadine but not astemizole blocked the slowly activating component of the delayed rectifier, IKs (58.4 +/- 3.1%), and the inward rectifier, IK1 (20.5 +/- 3.4%). Chlorpheniramine and pyrilamine blocked IKr relatively weakly (IC50 = 1.6 and 1.1 mumol/L, respectively) and IKs and IK1 less than 20% at 10 mumol/L. Astemizole and terfenadine (1.0 to 3.0 mg/kg IV) significantly prolonged the QTc interval and ventricular effective refractory period in vivo. Chlorpheniramine and pyrilamine (< or = 3.0 mg/kg) did not significantly affect these parameters. Block of repolarizing K+ currents, particularly IK1, by astemizole and terfenadine produces reverse rate-dependent prolongation of action potential duration and development of early afterdepolarizations, delays ventricular repolarization, and may underlie the development of torsade de pointes ventricular arrhythmias observed with the use and abuse of these agents.
- Published
- 1995
- Full Text
- View/download PDF
34. Cardiac electrophysiologic and antiarrhythmic actions of two long-acting spirobenzopyran piperidine class III agents, L-702,958 and L-706,000 [MK-499].
- Author
-
Lynch JJ Jr, Wallace AA, Stupienski RF 3rd, Baskin EP, Beare CM, Appleby SD, Salata JJ, Jurkiewicz NK, Sanguinetti MC, and Stein RB
- Subjects
- Animals, Dogs, Electrocardiography drug effects, Female, Ferrets, Guinea Pigs, Heart physiology, Hemodynamics drug effects, In Vitro Techniques, Male, Molecular Structure, Myocardial Ischemia physiopathology, Anti-Arrhythmia Agents pharmacology, Benzopyrans pharmacology, Heart drug effects, Piperidines pharmacology
- Abstract
The cardiac electrophysiologic and antiarrhythmic actions of two Class III ketone- and alcohol-containing spirobenzopyran piperidine analogs, L-702,958 and L-706,000 [MK-499], respectively, were assessed in vitro and in vivo. L-702,958 and L-706,000 [MK-499] selectively blocked the rapidly activating component of the delayed rectifier K+ current in guinea pig isolated ventricular myocytes (IC50 values, 14.6 and 43.9 nM, respectively), and prolonged effective refractory period in ferret isolated papillary muscles (EC25 values, 10.5 and 53.8 nM, respectively). In anesthetized dogs, L-702,958 and L-706,000 [MK-499] increased ventricular refractory periods (ED20 values, 3.3 and 9.2 micrograms/kg i.v., respectively) and concomitantly increased ECG QT interval and left ventricular+dP/dt. Cumulative i.v. administrations of up to 100 micrograms/kg of L-702,958 and 300 micrograms/kg L-706,000 [MK-499] in anesthetized dogs increased atrial and ventricular refractoriness and prolonged the ECG QT interval, but did not alter atrial, atrioventricular nodal, His-Purkinje or ventricular conduction indices. In anesthetized dogs studied chronically (9.2 +/- 1.1 days) after anterior myocardial infarction, the cumulative i.v. administrations of 100 micrograms/kg of L-702,958 and 300 of micrograms/kg L-706,000 [MK-499] suppressed the induction of ventricular tachyarrhythmia by programmed ventricular stimulation (suppression rates: 8 of 10, 80% and 9 of 11, 82%, respectively) and reduced the incidence of lethal ventricular arrhythmias (incidence of lethal ischemic arrhythmias: 4 of 10, 40% and 1 of 11 9%, respectively, compared to 34 of 40, 85%, in vehicle controls. L-702,958 and L-706,000 [MK-499] (cumulative 100 and 300 micrograms/kg i.v., respectively) did not facilitate the induction of arrhythmias by programmed ventricular stimulation in postinfarction dogs. After equivalently effective p.o. doses in conscious dogs, L-702,958 (10 micrograms/kg) and L-706,000 [MK-499] (30 micrograms/kg) increased ECG QT interval with long durations of action of approximately 9 and 14 hr, respectively. L-706,000 [MK-499] elicited a more consistent and sustained prolongation of the QT interval than L-702,958. These findings show that both L-702,958 and L-706,000 [MK-499] are potentially useful agents for the prevention of malignant ventricular arrhythmias in the setting of myocardial ischemic injury.
- Published
- 1994
35. K+ currents expressed from the guinea pig cardiac IsK protein are enhanced by activators of protein kinase C.
- Author
-
Zhang ZJ, Jurkiewicz NK, Folander K, Lazarides E, Salata JJ, and Swanson R
- Subjects
- Amino Acid Sequence, Animals, Base Sequence, Cloning, Molecular, DNA, Complementary genetics, Enzyme Activation, Female, Guinea Pigs, Humans, Ion Channels metabolism, Membrane Proteins genetics, Mice, Molecular Sequence Data, Mutagenesis, Site-Directed, Oocytes metabolism, Rats, Xenopus, Membrane Proteins metabolism, Myocardium metabolism, Potassium metabolism, Potassium Channels, Potassium Channels, Voltage-Gated, Protein Kinase C metabolism
- Abstract
We have isolated cardiac cDNA and genomic clones encoding the guinea pig IsK protein. The deduced amino acid sequence is approximately 78% identical to the rat, mouse, and human variants of this channel, and the structure of the gene encoding the protein is also similar to that in other species. For example, the gene is present only once in the haploid genome, the protein-coding sequence is present on a single uninterrupted exon, an intron exists in the 5' untranslated domain, and multiple alternative polyadenylation sites are used in processing the transcript. Expression of the guinea pig protein in Xenopus oocytes results in a slowly activating, voltage-dependent K+ current, IsK, similar to those expressed previously from the rat, mouse, and human genes. However, in sharp contrast to the rat and mouse currents, activation of protein kinase C with phorbol esters increases the amplitude of the guinea pig IsK current, analogous to its effects on the endogenous IKs current in guinea pig cardiac myocytes. Mutagenesis of the guinea pig cDNA to alter four cytoplasmic amino acid residues alters the phenotype of the current response to protein kinase C from enhancement to inhibition, mimicking that of rat and mouse IsK currents. This mutation is consistent with reports that phosphorylation of Ser-102 by protein kinase C decreases the current amplitude. These data explain previously reported differences in the regulatory properties between recombinant rat or mouse IsK channels and native guinea pig IKs channels and provide further evidence that the IsK protein forms the channels that underlie the IKs current in the heart.
- Published
- 1994
- Full Text
- View/download PDF
36. Species variants of the IsK protein: differences in kinetics, voltage dependence, and La3+ block of the currents expressed in Xenopus oocytes.
- Author
-
Hice RE, Folander K, Salata JJ, Smith JS, Sanguinetti MC, and Swanson R
- Subjects
- Animals, Electric Conductivity, Female, Humans, In Vitro Techniques, Kinetics, Lanthanum pharmacology, Membrane Potentials, Mice, Oocytes drug effects, Oocytes metabolism, Potassium Channels drug effects, Potassium Channels metabolism, Rats, Species Specificity, Xenopus laevis, Membrane Proteins metabolism, Potassium Channels, Voltage-Gated
- Abstract
We have compared the slowly activating K+ currents (IsK) resulting from the expression of the human, mouse, or rat IsK proteins in Xenopus oocytes, utilizing natural, species-dependent sequence variations to initiate structure-function studies of this channel. Differences were found between the human and rodent currents in their voltage dependence, kinetics, and sensitivity to external La3+. The current/voltage relationships of the human and rat IsK currents differed significantly, with greater depolarizations required for activation of the human channel. The first 30 s of activation during depolarizations to potentials between -10 and +40 mV was best described by a triexponential function for each of the three species variants. The activation rates were, however, significantly faster for the human current than for either of the rodent forms. Similarly, deactivation kinetics were best described as a biexponential decay for each of the species variants but the human currents deactivated more rapidly than the rodent currents. The human and the rodent forms of IsK were also differentially affected by external La3+. Low concentrations (10, 50 microM) rapidly and reversibly reduced the magnitude of the mouse and rat currents during a test depolarization and increased the deactivation rates of the tail currents. In contrast, the magnitude and deactivation rates of the human IsK currents were unaffected by 50 microM La3+.
- Published
- 1994
- Full Text
- View/download PDF
37. RWJ 26629, a new potassium channel opener and vascular smooth muscle relaxant: a potential antihypertensive and antianginal agent.
- Author
-
Katz LB, Giardino EC, Salata JJ, Moore JB Jr, and Falotico R
- Subjects
- Angina Pectoris drug therapy, Animals, Benzopyrans pharmacology, Bronchoconstriction drug effects, Calcium Channel Blockers pharmacology, Cromakalim, Dogs, Dose-Response Relationship, Drug, Female, Ferrets, Gastrointestinal Motility drug effects, Guinea Pigs, Heart Atria drug effects, Macaca mulatta, Male, Mice, Mice, Inbred Strains, Muscle, Smooth, Vascular physiology, Nitrendipine metabolism, Papillary Muscles drug effects, Pilocarpine pharmacology, Pyrroles pharmacology, Rabbits, Rats, Rats, Inbred SHR, Rats, Sprague-Dawley, Rubidium pharmacokinetics, Rubidium Radioisotopes, Vasodilator Agents pharmacology, Antihypertensive Agents pharmacology, Muscle Relaxation drug effects, Muscle, Smooth, Vascular drug effects, Potassium Channels drug effects, Pyrans pharmacology, Thiophenes pharmacology
- Abstract
The effects of trans-5,6-dihydro-6-hydroxy-5,5-dimethyl-2-nitro-7-(2-oxopiperidin -1-yl)-7H- thieno[3,2-b]pyran (RWJ 26629) were compared with those of the standard potassium channel opener cromakalim and several standard calcium channel blockers. RWJ 26629 lowered the mean arterial blood pressure in conscious spontaneously hypertensive (ED30 = 10 micrograms/kg p.o. or 8 micrograms/kg i.v.) and renal hypertensive (15 micrograms/kg p.o.) rats, conscious renal hypertensive (ED20 = 4 micrograms/kg p.o.) and normotensive (ED20 = 5 micrograms/kg p.o. or 2 micrograms/kg i.v.) dogs and anesthetized rhesus monkeys (ED20 = 6 micrograms/kg i.v.). RWJ 26629 was more potent than cromakalim and had a maximal activity greater than the calcium channel blockers. At antihypertensive doses, RWJ 26629 had no significant effect on cardiac force, cardiac output, stroke volume or stroke work in dogs and had little or no effect on renal, carotid or femoral blood flow or vascular resistance. RWJ 26629 was also selective for antihypertensive activity in rats compared with its ability to inhibit intestinal motility. However, RWJ 26629 did relax contracted pulmonary smooth muscle in vivo at antihypertensive doses. All compounds tested caused reflex tachycardia in conscious dogs, although this effect was lowest for RWJ 26629. Most importantly, RWJ 26629 potently and selectively increased coronary blood flow with a potency and duration of action greater than that of cromakalim or nifedipine without affecting contractile force. In vitro, RWJ 26629 selectively relaxed precontracted coronary arteries compared with its effect on femoral arteries.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1993
38. In vivo cardiac electrophysiologic effects of RWJ 29009, a new potassium-channel activator, in comparison to cromakalim and nicardipine.
- Author
-
Damiano BP, Stump GL, Cheung WM, and Salata JJ
- Subjects
- Animals, Antihypertensive Agents pharmacology, Benzopyrans pharmacology, Cromakalim, Dogs, Female, Male, Nicardipine pharmacology, Pyrroles pharmacology, Electrocardiography drug effects, Heart Conduction System drug effects, Piperidones pharmacology, Potassium Channels drug effects, Pyrans, Thiophenes, Vasodilator Agents pharmacology
- Abstract
RWJ 29009 is a new potassium channel activator with prominent coronary and peripheral vasodilating actions. Because of the potential direct cardiac electrophysiologic actions of increased potassium conductance in myocardium, we evaluated the effects of RWJ 29009 on cardiac conduction and refractoriness in comparison to its vasodilator activity in anesthetized, open-chest dogs. We assessed effects during both intrinsic sinus rhythm and during constant atrial pacing. RWJ 29009 markedly increased coronary blood flow and decreased mean arterial blood pressure (MAP) dose dependently (0.3-10 micrograms/kg intravenously, i.v.). RWJ 29009 had no effect on PR interval but decreased AV-nodal conduction time (AH) and Wenkebach cycle length slightly. RWJ 29009 decreased QT interval, left ventricular (LV) monophasic action potential duration (APD), and ventricular and atrial refractory period. These effects were consistent with shortening of cardiac repolarization. RWJ 29009 had no effect on QRS or His-Purkinje conduction time. Cromakalim had a qualitatively similar profile but was much less potent (3-300 micrograms/kg i.v.). In addition, the effects of cromakalim on repolarization parameters were somewhat less marked than those of RWJ 29009. Nicardipine also markedly increased coronary blood flow and decreased arterial pressure (10-300 micrograms/kg i.v.). Unlike the potassium channel activators, nicardipine (100-300 micrograms/kg), did not affect cardiac repolarization, but increased PR and AH interval, and Wenkebach cycle length (WENK) and reduced heart rate (HR) consistent with calcium channel blockade. These results indicate that RWJ 29009, like cromakalim, increases coronary blood flow at low doses without substantial electrophysiologic effects. Electrophysiologic effects observed at higher doses indicated a shortening of repolarization, expectedly produced by potassium channel activation in cardiac tissue.
- Published
- 1993
- Full Text
- View/download PDF
39. Synthesis and SAR of 6-substituted purine derivatives as novel selective positive inotropes.
- Author
-
Press JB, Falotico R, Hajos ZG, Sawyers RA, Kanojia RM, Williams L, Haertlein B, Kauffman JA, Lakas-Weiss C, and Salata JJ
- Subjects
- Animals, Blood Pressure drug effects, Dogs, Ferrets, Heart Rate drug effects, Male, Mercaptopurine chemical synthesis, Mercaptopurine pharmacology, Molecular Structure, Papillary Muscles drug effects, Papillary Muscles physiology, Piperazines pharmacology, Sodium Channels drug effects, Sodium Channels physiology, Stimulation, Chemical, Structure-Activity Relationship, Cardiotonic Agents chemical synthesis, Cardiotonic Agents pharmacology, Mercaptopurine analogs & derivatives, Myocardial Contraction drug effects, Piperazines chemical synthesis, Purines chemical synthesis, Purines pharmacology
- Abstract
A series of purine derivatives was prepared and examined for selective inotropic activity in vitro and in vivo. Thioether-linked derivatives were superior to their oxygen and nitrogen isosteres. Substitution of electron-withdrawing groups on the benzhydryl moiety of these agents increased potency. The best compound of the study, 17 (carsatrin), was examined further and demonstrated selective oral activity as a positive inotrope. These compounds are presumed to act by affecting the kinetics of the cardiac sodium channel by analogy to the prototypic agent DPI 201106 (1). Their high selectivity for increasing contractile force and dP/dt without affecting blood pressure or heart rate is consistent with this mechanism. Carsatrin (17) was selected as a potential development candidate.
- Published
- 1992
- Full Text
- View/download PDF
40. Basis for tetrodotoxin and lidocaine effects on action potentials in dog ventricular myocytes.
- Author
-
Wasserstrom JA and Salata JJ
- Subjects
- Action Potentials drug effects, Animals, Dogs, Drug Interactions, Heart Ventricles drug effects, In Vitro Techniques, Ion Channels drug effects, Ion Channels physiology, Kinetics, Microelectrodes, Sodium metabolism, Ventricular Function, Heart physiology, Lidocaine pharmacology, Tetrodotoxin pharmacology
- Abstract
We studied the effects of tetrodotoxin (TTX) and lidocaine on transmembrane action potentials and ionic currents in dog isolated ventricular myocytes. TTX (0.1-1 x 10(-5) M) and lidocaine (0.5-2 x 10(-5) M) decreased action potential duration, but only TTX decreased the maximum rate of depolarization (Vmax). Both TTX (1-2 x 10(-5) M) and lidocaine (2-5 x 10(-5) M) blocked a slowly inactivating toward current in the plateau voltage range. The voltage- and time-dependent characteristics of this current are virtually identical to those described in Purkinje fibers for the slowly inactivating inward Na+ current. In addition, TTX abolished the outward shift in net current at plateau potentials caused by lidocaine alone. Lidocaine had no detectable effect on the slow inward Ca2+ current and the inward K+ current rectifier, Ia. Our results indicate that 1) there is a slowly inactivating inward Na+ current in ventricular cells similar in time, voltage, and TTX sensitivity to that described in Purkinje fibers; 2) both TTX and lidocaine shorten ventricular action potentials by reducing this slowly inactivating Na+ current; 3) lidocaine has no additional actions on other ionic currents that contribute to its ability to abbreviate ventricular action potentials; and 4) although both agents shorten the action potential by the same mechanism, only TTX reduces Vmax. This last point suggests that TTX produces tonic block of Na+ current, whereas lidocaine may produce state-dependent Na+ channel block, namely, blockade of Na+ current only after Na+ channels have already been opened (inactivated-state block).
- Published
- 1988
- Full Text
- View/download PDF
41. In vivo acetylcholine turnover in rat heart.
- Author
-
Brown OM and Salata JJ
- Subjects
- Acetylcholine analysis, Animals, Choline analysis, Choline metabolism, Gas Chromatography-Mass Spectrometry, Male, Myocardium analysis, Postmortem Changes, Rats, Rats, Inbred Strains, Acetylcholine biosynthesis, Myocardium metabolism
- Abstract
The in vivo uptake of choline (Ch) and synthesis of acetylcholine (ACh) in rat heart were studied using a pyrolysis mass fragmentography (PMF) method. Deuterium labeled Ch was pulse injected (i.v.) into anesthetized rats. Labeled and unlabeled Ch and ACh were measured by PMF in hearts at various times following injection. From these data we calculated the specific activities of Ch and ACh, rate constants for ACh and turnover rates of ACh. After an initial equilibration period of approximately 2 min, the specific activities of Ch and ACh decayed in a parallel manner with half-times of 28.2 and 28.8 min respectively. Between 2 and 60 min the calculated ACh turnover rate was 0.144 nmol/g/min. Unlike brain Ch, heart Ch levels are very stable with time following sacrifice. No advantage was found in using microwave irradiation to stabilize heart ACh and Ch content.
- Published
- 1983
- Full Text
- View/download PDF
42. Effects of sympathetic tone on vagally induced phasic changes in heart rate and atrioventricular node conduction in the anesthetized dog.
- Author
-
Salata JJ, Gill RM, Gilmour RF Jr, and Zipes DP
- Subjects
- Animals, Cardiac Pacing, Artificial, Dogs, Electric Stimulation, Female, Male, Myocardial Contraction, Neural Conduction, Reaction Time physiology, Stellate Ganglion physiology, Time Factors, Atrioventricular Node physiology, Heart Conduction System physiology, Heart Rate, Sympathetic Nervous System physiology, Vagus Nerve physiology
- Abstract
We examined the effects of stellate ganglia stimulation on the phase-dependent chronotropic and dromotropic responses to brief vagal bursts in open-chest anesthetized dogs. Stellate stimulation affected the phasic vagal effects on heart rate by shortening the latent period, shifting the phase at which maximum decrease in heart rate occurred to earlier phases, and reducing the maximum decrease in heart rate. These effects were due primarily to an increase in the basic heart rate. No significant sympathetic-parasympathetic interaction occurred for heart rate, indicating that accentuated antagonism did not occur with brief vagal bursts. Stellate stimulation primarily decreased the amplitude of the phasic vagal effects on atrioventricular nodal conduction, regardless of the underlying heart rate, and a significant sympathetic-parasympathetic interaction was associated with this effect. The peak of the phase-dependent vagal effects on heart rate and atrioventricular nodal conduction were phase-shifted with one another. From these findings, we postulate the small changes in sympathetic tone might shift the predominant phase-dependent vagal effect from one on heart rate to one on atrioventricular nodal conduction. Furthermore, our results suggest that dynamic vagal control of heart rate and atrioventricular node conduction involves both phase-dependent and phase-independent factors. Sympathetic activity appears to affect only the phase-independent factor(s) in the control of heart rate, whereas it affects both phase-dependent and phase-independent factors in the control of atrioventricular node conduction.
- Published
- 1986
- Full Text
- View/download PDF
43. Positive inotropic and hemodynamic properties of flosequinan, a new vasodilator, and a sulfone metabolite.
- Author
-
Falotico R, Haertlein BJ, Lakas-Weiss CS, Salata JJ, and Tobia AJ
- Subjects
- Amrinone pharmacology, Anesthesia, Animals, Ferrets, Heart Failure drug therapy, Heart Failure physiopathology, Heart Rate drug effects, In Vitro Techniques, Infusions, Intravenous, Male, Milrinone, Papillary Muscles drug effects, Pentobarbital, Pyridones pharmacology, Hemodynamics drug effects, Myocardial Contraction drug effects, Quinolines pharmacology, Vasodilator Agents pharmacology
- Abstract
Flosequinan, a new orally active vasodilator, and its sulfone metabolite were evaluated for inotropic activity in isolated ferret papillary muscles and pentobarbital anesthetized open-chest dogs. In vitro, flosequinan and its sulfone derivative increased tension development in a concentration-dependent manner (1-50 microM) in electrically stimulated papillary muscles pretreated with the beta-adrenergic blocking agent atenolol (2 microM). Peak increases in tension of 75 +/- 17%, and 111 +/- 46% with potencies (EC50) of 15 and 10 microM were observed for flosequinan and its metabolite, respectively. In vivo, flosequinan increased left ventricular dP/dtmax (74 +/- 12%) and right ventricular contractile force (CF) (104 +/- 10%) after administration of 1.875 mg/kg, i.v. Inotropic activity was dose-dependent and remained elevated for at least 60 min postinfusion. Flosequinan also increased heart rate (HR) (14 +/- 2%) and reduced mean arterial pressure (-9 +/- 3%). The i.v. potency of flosequinan (ED50 = 0.45 mg/kg) and its metabolite (ED50 = 0.38 mg/kg) were similar to that of the inotropic vasodilator amrinone (ED50 = 0.38 mg/kg). Inotropic activity was not significantly altered by pretreatment with propranolol (0.5 mg/kg) and atropine (1.0 mg/kg), further supporting the in vitro data indicating that flosequinan can directly stimulate myocardial contractility independent of beta-adrenergic receptor activation. Additional hemodynamic studies were conducted in an acute heart failure model produced by an overdose of propranolol. Flosequinan (2 mg/kg, i.v.) increased cardiac output (CO) (50 +/- 9%) and stroke volume (SV) (29 +/- 8%) while reducing total peripheral vascular resistance (TPR) (-36 +/- 4%), right atrial pressure (-62 +/- 5%), and left ventricular end-diastolic pressure (LVEDP) (-41 +/- 2%).(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1989
- Full Text
- View/download PDF
44. Effects of 4-aminopyridine on rate-related depression of cardiac action potentials.
- Author
-
Gilmour RF Jr, Salata JJ, and Davis JR
- Subjects
- 4-Aminopyridine, Action Potentials drug effects, Animals, Caffeine pharmacology, Cats, Cesium pharmacology, Dogs, Female, Heart Atria, Isoproterenol pharmacology, Male, Papillary Muscles drug effects, Purkinje Fibers drug effects, Rats, Rats, Inbred Strains, Aminopyridines pharmacology, Chlorides, Heart drug effects
- Abstract
Canine cardiac Purkinje fibers and atrial trabeculae and rat and cat papillary muscles superfused with a hyperkalemic, hypoxic, and acidotic Tyrode solution were depolarized to membrane potentials (-70 to -60 mV) at which action potential amplitude declined as the coupling intervals of pacing stimuli were prolonged from 500 to 4,500 ms. The rate-related decline of action potential amplitude appeared to be due to time-dependent recovery of the early outward current rather than to a decrease in inward calcium current, since it was prevented by 4-aminopyridine (1.0 mM), but not by isoproterenol (1.0 microM), caffeine (5.0 mM), or CsCl (5-20 mM) and it was accompanied by an exponential increase of developed tension. Experiments using Purkinje fibers mounted in a single sucrose gap chamber demonstrated that the rate-related decline of action potential amplitude was maximal at membrane potentials between -70 and -40 mV and was negligible at less negative or more negative membrane potentials. These results may pertain to the mechanism for deceleration-dependent bundle branch block.
- Published
- 1986
- Full Text
- View/download PDF
45. Dynamic vagal control of pacemaker activity in the mammalian sinoatrial node.
- Author
-
Jalife J, Slenter VA, Salata JJ, and Michaels DC
- Subjects
- Acetylcholine physiology, Animals, Cats, Electric Stimulation, Electrophysiology, Membrane Potentials, Propranolol pharmacology, Rabbits, Sheep, Time Factors, Heart Rate, Sinoatrial Node physiology, Vagus Nerve physiology
- Abstract
Dynamic heart rate control by parasympathetic nervous input involves feedback mechanisms and reflex bursting of efferent cardiac vagal fibers. Periodic vagal bursting induces phasic changes in sinoatrial cycle length and can entrain the pacemaker to beat at periods that may be identical to those of the vagal burst. We investigated the electrophysiological basis of these phenomena in isolated sinus node preparations (rabbit, cat, and sheep). In the presence of propranolol (3.9 X 10(-6)M), relatively brief (50-150 msec) trains of stimuli, applied onto the endocardial surface of the preparation, activated postganglionic vagal terminals and induced a brief hyperpolarization of sinoatrial pacemaker cells. This vagally mediated hyperpolarization could alter the pacemaker rhythm by an amount that depended on its duration and its position in the cycle, as well as on the duration of the free-running pacemaker period. When the free-running period was sufficiently long and the hyperpolarization was induced sufficiently early in the spontaneous cycle, a "paradoxical" acceleration of the pacemaker rhythm ensued. Phasic changes were plotted on phase-response curves, constructed by scanning systematically the sinoatrial pacemaker period with single or repetitive vagal trains. These phase-response curves enabled us to predict the entrainment characteristics and the levels of synchronization of the pacemaker to the vagal periodicity. The overall data explain the cellular mechanisms involved in the phasic effects of brief vagal discharges on sinoatrial periodicity, and provide conclusive evidence for the prediction that repetitive vagal input is capable of forcing the cardiac pacemaker to beat at rates that can be faster or slower than the intrinsic pacemaker rate. These data should improve our knowledge of the dynamic control of heart rate by neural reflexes and aid in our understanding of rhythm disturbances generated by the interaction of the cardiac pacemaker with vagal activity.
- Published
- 1983
- Full Text
- View/download PDF
46. Amantadine-induced diastolic depolarization and automaticity in ventricular muscle.
- Author
-
Salata JJ, Jalife J, Megna JL, and Alperovich G
- Subjects
- Action Potentials drug effects, Animals, Catecholamines metabolism, Cats, Diastole, Dogs, Electrophysiology, Heart physiology, Lidocaine pharmacology, Membrane Potentials drug effects, Rabbits, Rana pipiens, Tetrodotoxin pharmacology, Verapamil pharmacology, Amantadine pharmacology, Ventricular Function
- Abstract
We studied the cardiac effects of amantadine, an antiviral and anti-Parkinson drug. Amantadine hydrochloride (100--800 microM) produced significant changes in the electrophysiological properties of isolated ventricular muscle preparations from frog, rabbit, cat, dog, and calf. At relatively low concentrations (100--300 microM), the drug increased action potential duration, decreased action potential amplitude and maximum diastolic potential, and induced phase 4 depolarization. Amantadine also caused subthreshold diastolic depolarizations, apparent upon cessation of stimulation in all preparations studied. The amplitude of the diastolic depolarizations increased as a function of time and/or concentration of drug, eventually reached threshold, and spontaneous activity ensued. In the steady state, amantadine-induced spontaneous activity was rather stable, and the rate was dependent upon the amantadine and external potassium concentrations, as well as the membrane potential. In the absence of stimulation, amantadine-induced spontaneous activity occurred abruptly or could be triggered by a single stimulus, often occurring in a "bursting" fashion that appeared to originate from multiple discrete foci. All actions of amantadine were rapidly reversed upon washout. Propranolol had no effect on the actions of the drug. Amantadine-induced spontaneous activity was unaffected by lidocaine, diminished by TTX, and reduced or abolished by verapamil. The results indicate that amantadine can directly alter the membrane properties of ventricular muscle, possibly due to an effect on potassium conductance. Furthermore, amantadine can be used as a tool to study the ionic basis of ventricular automaticity and to model cellular mechanisms of ventricular rhythm disturbances.
- Published
- 1982
- Full Text
- View/download PDF
47. Rate-related suppression and facilitation of conduction in isolated canine cardiac Purkinje fibers.
- Author
-
Gilmour RF Jr, Salata JJ, and Zipes DP
- Subjects
- Animals, Bundle of His physiopathology, Cardiac Pacing, Artificial, Diastole, Dogs, Female, Male, Bundle-Branch Block physiopathology, Electrocardiography, Heart Conduction System physiopathology, Heart Rate, Purkinje Fibers physiopathology
- Abstract
Previous studies have shown that antegrade conduction through damaged His Purkinje tissue may be suppressed following rapid ventricular pacing (overdrive suppression of conduction). We studied this phenomenon using isolated Purkinje fibers placed in a three-chamber bath. Superfusates for the left, middle, and right segments of the fiber were altered to produce action potentials that resembled those of normal bundle branch, damaged His bundle, and normal His bundle, respectively. To produce anisotropic conduction, the left segment of the fiber was adjusted to be three to four times longer than the right segment. Pacing the right segment at intermediate rates produced maximal action potential amplitude in the middle segment and 1:1 right-to-left conduction, whereas pacing at faster or slower rates reduced action potential amplitude and produced block. Pacing the left segment at fast or slow rates also reduced action potential amplitude in the middle segment, but conduction was maintained (anisotropy). After rapid or slow left segment pacing, action potential amplitude in the middle segment remained low during subsequent right segment pacing at intermediate rates, and transient block occurred (overdrive or underdrive suppression of conduction). With time, action potential amplitude normalized and conduction resumed. In other more severely depressed preparations, conduction block occurred even at intermediate right segment pacing rates prior to left segment pacing. Under these conditions, pacing the left segment at intermediate rates increased action potential amplitude in the middle segment and temporarily permitted 1:1 conduction at intermediate right segment pacing rates (overdrive facilitation of conduction).(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1985
- Full Text
- View/download PDF
48. Dantrolene sodium: effects on isolated cardiac tissues.
- Author
-
Salata JJ, Wasserstrom JA, and Jalife J
- Subjects
- Action Potentials drug effects, Animals, Cats, Dogs, Stimulation, Chemical, Time Factors, Dantrolene pharmacology, Heart drug effects, Myocardial Contraction drug effects
- Abstract
The effects of dantrolene sodium on dog Purkinje fibers, cat atrial and ventricular muscles were studied. Action potential duration was significantly increased and contractility was significantly decreased by dantrolene in all three types of tissue. The plateau phase of Purkinje fiber and occasionally atrial action potential was slightly depressed. Dantrolene sodium had no significant effect on resting membrane potential, action potential amplitude or upstroke velocity of phase 6. The negative inotropic effects were most pronounced in Purkinje fibers, followed by atrial muscle while papillary muscles were least sensitive. Contractile force of Purkinje fibers was decreased by relatively the same amount at all frequencies of stimulation. At faster rates, atrial and ventricular muscle contractility was depressed relatively more than at slower rates. Slow response action potentials in cat papillary muscle were diminished slightly, but this effect was not significant. All drug effects took 10 to 15 min to develop, reached a steady state after 30 to 40 min, and were irreversible upon washout. Increasing the extracellular calcium concentration reversed the dantrolene-induced changes. These findings suggest that effects of dantrolene are mediated in part by a decrease in the intracellular free calcium concentration in cardiac tissue.
- Published
- 1983
- Full Text
- View/download PDF
49. "Fade" of hyperpolarizing responses to vagal stimulation at the sinoatrial and atrioventricular nodes of the rabbit heart.
- Author
-
Salata JJ and Jalife J
- Subjects
- Animals, Atrioventricular Node metabolism, Cardiac Pacing, Artificial, Electrophysiology, In Vitro Techniques, Membrane Potentials, Rabbits, Receptors, Muscarinic metabolism, Sinoatrial Node metabolism, Time Factors, Atrioventricular Node physiology, Electric Stimulation, Heart Conduction System physiology, Sinoatrial Node physiology, Vagus Nerve physiology
- Abstract
Previous studies have suggested that maintained vagal stimulation or acetylcholine infusion results in a fade of responses in the sinoatrial node but not in the atrioventricular node, implying different muscarinic receptor subtypes in the two regions. We investigated this hypothesis in 23 isolated rabbit atrial preparations made quiescent by continuous superfusion with verapamil (1 microgram/ml). Transmembrane potentials were recorded simultaneously from cells in the sinoatrial pacemaker region and from the "N" region of the atrioventricular node. Postganglionic vagal stimulation was achieved by the application of trains of pulses (50-150 microseconds; 10-20 V; 200 Hz). Simultaneous application of long-lasting (1-10 sec) vagal trains produced hyperpolarizations which were nearly identical for both nodal regions. Maximal hyperpolarizations (approximately or equal to 24 mV for sinoatrial node; 26 mV for atrioventricular node) were reached about 500 msec after initiation of the vagal train. Thereafter, hyperpolarizations faded, following a biphasic time course, and thus displaying two different time constants, one fast (tau fast = 580 msec for sinoatrial node; 550 msec for atrioventricular node), and one slow (tau slow = 9.2 sec for both sinoatrial and atrioventricular nodes). Hyperpolarizations during brief (200-msec) but repetitive vagal trains also faded biphasically, but approached a steady state much more rapidly than responses to long-lasting trains. Recovery from hyperpolarization decay occurred rather slowly and was linear. Our results demonstrate that the membrane potential responses to vagal stimulation in the atrioventricular node are indistinguishable from those in the sinoatrial node, and suggest that similar muscarinic receptors are operative in both regions. These phenomena may play an important role in the response of the cardiac conducting system to direct or reflexly mediated vagal input.
- Published
- 1985
- Full Text
- View/download PDF
50. Effects of dantrolene sodium on the electrophysiological properties of canine cardiac Purkinje fibers.
- Author
-
Salata JJ and Jalife J
- Subjects
- Action Potentials drug effects, Animals, Anti-Arrhythmia Agents, Calcium pharmacology, Dogs, Electric Stimulation, Female, In Vitro Techniques, Male, Membrane Potentials drug effects, Myocardial Contraction drug effects, Osmolar Concentration, Time Factors, Dantrolene pharmacology, Heart Conduction System drug effects, Purkinje Fibers drug effects
- Abstract
Dantrolene sodium at concentrations between 8.8 and 35.1 microM produced rather selective changes in the electrophysiological properties of isolated dog Purkinje fibers. The action potential duration at 90% repolarization and effective refractory period of normally polarized fibers were increased in a dose- and frequency-dependent fashion. The plateau phase of the action potential was significantly depressed and this effect coincided with a marked decrease in the strength of contraction. Dantrolene sodium had no significant effect on resting membrane potential, upstroke velocity of phase O, conduction velocity or pacemaker activity of Purkinje fibers. Dantrolene diminished or abolished "slow response" action potentials produced by superfusion with 18 mM K+ Tyrode's solution containing 10(-7) M isoproterenol. Drug effects took 10 to 15 min to become apparent, reached a steady-state after 45 to 60 min and were not reversible even after 2 hr of washout with drug-free Tyrode's solution. In contrast, increasing the [Ca++]0 produced nearly a complete reversal of the dantrolene-induced changes. These results suggest that dantrolene produces its effects by interfering with the slow inward current. Thus, dantrolene may be similar in action to other slow channel blocking agents, such as verapamil, and may be useful as an antiarrhythmic agent.
- Published
- 1982
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.