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Even though rodents are accessible model animals, their electrophysiological properties are deeply different from those of humans, making the translation of rat studies to humans rather difficult. We compared the mechanisms of ventricular repolarization in various animal models to those of humans by measuring cardiac ventricular action potentials from ventricular papillary muscle preparations using conventional microelectrodes and applying selective inhibitors of various potassium transmembrane ion currents. Inhibition of the [I.sub.K1] current (10 [micro]mol/L barium chloride) significantly prolonged rat ventricular repolarization, but only slightly prolonged it in dogs, and did not affect it in humans. On the contrary, [I.sub.Kr] inhibition (50 nmol/L dofetilide) significantly prolonged repolarization in humans, rabbits, and dogs, but not in rats. Inhibition of the [I.sub.Kur] current (1 [micro]mol/L XEN-D0101) only prolonged rat ventricular repolarization and had no effect in humans or dogs. Inhibition of the [I.sub.Ks] (500 nmol/L HMR-1556) and [I.sub.to] currents (100 [micro]mol/L chromanol-293B) elicited similar effects in all investigated species. We conclude that dog ventricular preparations have the strongest translational value and rat ventricular preparations have the weakest translational value in cardiac electrophysiological experiments. Key words: action potential duration, ion currents, human, comparison Les rongeurs constituent des modeles chez les animaux bien accessibles, mais leurs proprietes electrophysiologiques sont bien differentes de celles des humains, ce qui rend l'application des etudes chez le rat a l'humain plutot difficile. Nous avons compare les modes d'action de la repolarisation ventriculaire dans divers modeles chez les animaux a ceux des humains par l'enregistrement de potentiels d'action dans des preparations de muscle papillaire ventriculaire a l'aide de microelectrodes classiques, de meme que de l'application d'inhibiteurs selectifs de divers canaux potassiques transmembranaires. L'inhibition du courant [I.sub.K1] (chlorure de baryum a 10 [micro]M) entrainait une prolongationmarquee de la repolarisation ventriculaire chez le rat, mais seulement une legere prolongation chez le chien, sans effet sur ce parametre chez l'humain. Inversement, l'inhibition du courant [I.sub.Kr] (dofetilide a 50 nM) entrainait une prolongation marquee chez l'humain, le lapin et le chien, mais pas chez le rat. L'inhibition du courant [I.sub.Kur] (XEN-D0101 a 1 [micro]M) prolongeait la repolarisation ventriculaire uniquement chez le rat, sans effet chez l'humain ni chez le chien. L'inhibition des courants [I.sub.Ks] (HMR-1556 a 500 nM) et [I.sub.to] (chromanol-293B a 100 [micro]M) entrainait des effets similaires chez toutes les especes etudiees. Nous en arrivons a la conclusion que les preparations canines de ventricule permettent de realiser les experiences d'electrophysiologie cardiaque les plus robustes quant a leur application chez l'humain, alors que les moins robustes sur ce plan sont celles qui sont realisees a l'aide de preparations de ventricule de rat. [Traduit par la Redaction] Mots-cles : duree du potentiel d'action, courants ioniques, humain, comparaison, Introduction The translational value of electrophysiological experiments can be largely dependent on the animal model used (Varro et al. 1993), and some mammalian hearts are more similar to the human [...]

Aims: Atrial fibrillation (AF) is the most common chronic/recurrent arrhythmia, which significantly impairs quality of life and increases cardiovascular morbidity and mortality. Therefore, the aim of the present study was to investigate the properties of three repolarizing potassium currents which were shown to contribute to AF-induced electrical remodeling, i.e., the transient outward (Ito), inward rectifier (IK1) and acetylcholine-sensitive (IK,ACh) potassium currents in isolated atrial myocytes obtained from dogs either with sinus rhythm (SR) or following chronic atrial tachypacing (400/min)-induced AF. Methods: Atrial remodeling and AF were induced by chronic (4–6 weeks of) right atrial tachypacing (400/min) in dogs. Transmembrane ionic currents were measured by applying the whole-cell patch-clamp technique at 37 °C. Results: The Ito current was slightly downregulated in AF cells when compared with that recorded in SR cells. This downregulation was also associated with slowed inactivation kinetics. The IK1 current was found to be larger in AF cells; however, this upregulation was not statistically significant in the voltage range corresponding with atrial action potential (−80 mV to 0 mV). IK,ACh was activated by the cholinergic agonist carbachol (CCh; 2 µM). In SR, CCh activated a large current either in inward or outward directions. The selective IK,ACh inhibitor tertiapin (10 nM) blocked the outward CCh-induced current by 61%. In atrial cardiomyocytes isolated from dogs with AF, the presence of a constitutively active IK,ACh was observed, blocked by 59% with 10 nM tertiapin. However, in "AF atrial myocytes", CCh activated an additional, significant ligand-dependent and tertiapin-sensitive IK,ACh current. Conclusions: In our dog AF model, Ito unlike in humans was downregulated only in a slight manner. Due to its slow inactivation kinetics, it seems that Ito may play a more significant role in atrial repolarization than in ventricular working muscle myocytes. The presence of the constitutively active IK,ACh in atrial myocytes from AF dogs shows that electrical remodeling truly developed in this model. The IK,ACh current (both ligand-dependent and constitutively active) seems to play a significant role in canine atrial electrical remodeling and may be a promising atrial selective drug target for suppressing AF. [ABSTRACT FROM AUTHOR]

To understand the large inter-species variations in drug effects on repolarization, the properties of the rapid (IKr) and the slow (IKs) components of the delayed rectifier potassium currents were compared in myocytes isolated from undiseased human donor (HM), dog (DM), rabbit (RM) and guinea pig (GM) ventricles by applying the patch clamp and conventional microelectrode techniques at 37 °C. The amplitude of the E-4031-sensitive IKr tail current measured at −40 mV after a 1 s long test pulse of 20 mV, which was very similar in HM and DM but significant larger in RM and GM. The L-735,821-sensitive IKs tail current was considerably larger in GM than in RM. In HM, the IKs tail was even smaller than in DM. At 30 mV, the IKr component was activated extremely rapidly and monoexponentially in each studied species. The deactivation of the IKr component in HM, DM, and RM measured at −40 mV. After a 30 mV pulse, it was slow and biexponential, while in GM, the IKr tail current was best fitted triexponentially. At 30 mV, the IKs component activated slowly and had an apparent monoxponential time course in HM, DM, and RM. In contrast, in GM, the activation was clearly biexponential. In HM, DM, and RM, IKs component deactivation measured at −40 mV was fast and monoexponential, while in GM, in addition to the fast component, another slower component was also revealed. These results suggest that the IK in HM resembles that measured in DM and RM and considerably differs from that observed in GM. These findings suggest that the dog and rabbit are more appropriate species than the guinea pig for preclinical evaluation of new potential drugs expected to affect cardiac repolarization. [ABSTRACT FROM AUTHOR]

The addition of alloying elements is a crucial factor in improving the mechanical properties of pure copper, particularly in terms of enhancing its yield strength and hardness. This study examines the influence of scandium additions (up to 0.27 wt.%) on low-alloyed copper. Following the casting and solution-annealing processes, the alloys were quenched in water to maintain a supersaturated state. The mechanical properties were evaluated by tensile tests to measure the yield strength and the dynamic resonance method to determine the modulus of rigidity. Additionally, X-ray diffraction was utilized to analyze changes in lattice parameters, elucidating the structural modifications induced by scandium. This study dissects the parelastic and dielastic effects underlying the solid solution hardening mechanism, providing insights into how scandium alters copper's mechanical properties. The findings align with the solid solution hardening theories proposed by Fleischer and Labusch, providing a comprehensive understanding of the observed phenomena. [ABSTRACT FROM AUTHOR]

Activation of the parasympathetic nervous system has been reported to have an antiarrhythmic role during ischemiareperfusion injury by decreasing the arrhythmia triggers. Furthermore, it was reported that the parasympathetic neurotransmitter acetylcholine is able to modulate the ATP-dependent potassium current ([I.sub.K-ATP]), a crucial current activated during hypoxia. However, the possible significance of this current modulation in the antiarrhythmic mechanism is not fully clarified. Action potentials were measured using the conventional microelectrode technique from canine left ventricular papillary muscle and free-running Purkinje fibers, under normal and hypoxic conditions. Ionic currents were measured using the whole-cell configuration of the patch-clamp method. Acetylcholine at 5 [micro]mol/L did not influence the action potential duration (APD) either in Purkinje fibers or in papillary muscle preparations. In contrast, it significantly lengthened the APD and suppressed the Purkinje-ventricle APD dispersion when it was administered after 5 [micro]mol/L pinacidil application. Carbachol at 3 [micro]mol/L reduced the pinacidil-activated [I.sub.K-ATP] under voltage-clamp conditions. Acetylcholine lengthened the ventricular action potential under simulated ischemia condition. In this study, we found that acetylcholine inhibits the [I.sub.K-ATP] and thus suppresses the ventricle-Purkinje APD dispersion. We conclude that parasympathetic tone may reduce the arrhythmogenic substrate exerting a complex antiarrhythmic mechanism during hypoxic conditions. Key words: acetylcholine, Purkinje fibers, papillary muscles, hypoxia. On a rapporte que l'activation du systeme nerveux parasympathique joue un role antiarythmique pendant l'ischemie reperfusion par l'inhibition des declencheurs des arythmies. En outre, on a rapporte que l'acetylcholine, neurotransmetteur parasympathique, est en mesure de moduler le courant potassique ATP dependant ([I.sub.K-ATP]), un courant essentiel qui est active pendant l'hypoxie. Cependant, la signification eventuelle de la modulation de ce courant dans le mode d'action antiarythmique n'a pas ete entierement clarifie. Nous avons mesure des potentiels d'action a l'aide de la technique de microelectrode classique dans le muscle papillaire et des fibres de Purkinje libres de ventricule gauche, en situations normale et hypoxique chez le chien. Nous avons mesure les courants ioniques a l'aide de la configuration sur cellules entieres de la methode de << patch clamp >>. L'acetylcholine a 5 [micro]mol/L n'avait pas d'influence sur la duree du potentiel d'action (DPA), tant dans les preparations de fibres de Purkinje que dans le muscle papillaire. Cependant, elle entrainait un allongement de la DPA et une inhibition complete de la dispersion de la DPA entre le Purkinje et le muscle quand elle etait administree apres l'administration de pinacidil a 5 [micro]mol/L. Le carbachol a 3 [micro]mol/L entrainait une diminution du courant [I.sub.K-ATP] active par le pinacidil sous clampage du voltage. L'acetylcholine entrainait un allongement de la DPA ventriculaire en situation d'ischemie reperfusion. Dans cette etude, nous avons observe que l'acetylcholine entraine une inhibition du courant [I.sub.K-ATP] et consequemment une inhibition complete de la dispersion de la DPA entre le muscle et le Purkinje. Nous en arrivons a la conclusion que le tonus parasympathique pourrait permettre d'attenuer le substrat arythmogene exerqant un mode d'action antiarythmique complexe en situation d'hypoxie. [Traduit par la Redaction] Mots-cles: acetylcholine, fibres de Purkinje, muscles papillaires, hypoxie., Introduction The parasympathetic nervous system has a crucial role in controlling the actual heart rate and impulse propagation by influencing the sinoatrial and atrioventricular nodes (Higgins et al. 1973). The [...]

Ibuprofen is a widely used nonsteroidal anti-inflammatory drug, which has recently been associated with increased cardiovascular risk, but its electrophysiological effects have not yet been properly studied in isolated cardiac preparations. We studied the effects of ibuprofen on action potential characteristics and several transmembrane ionic currents using the conventional microelectrode technique and the whole-cell configuration of the patch-clamp technique on cardiac preparations and enzymatically isolated ventricular myocytes. In dog (200 [micro]M; n = 6) and rabbit (100 [micro]M; n = 7) papillary muscles, ibuprofen moderately but significantly prolonged repolarization at 1 Hz stimulation frequency. In dog Purkinje fibers, repolarization was abbreviated and maximal rate of depolarization was depressed in a frequency-dependent manner. Levofloxacin (40 [micro]M) alone did not alter repolarization, but augmented the ibuprofen-evoked repolarization lengthening in rabbit preparations (n = 7). In dog myocytes, ibuprofen (250 [micro]M) did not significantly influence [I.sub.K1], but decreased the amplitude of [I.sub.to] and [I.sub.Kr] potassium currents by 28.2% (60 mV) and 15.2% (20 mV), respectively. Ibuprofen also depressed [I.sub.NaL] and [I.sub.Ca] currents by 19.9% and 16.4%, respectively. We conclude that ibuprofen seems to be free from effects on action potential parameters at lower concentrations. However, at higher concentrations it may alter repolarization reserve, contributing to the observed proarrhythmic risk in patients. Key words: ibuprofen, levofloxacin, repolarization reserve. L'ibuprofene est un anti-inflammatoire non steroidien largement utilise, qui a recemment ete associe avec un accroissement du risque cardiovasculaire, mais ses effets electrophysiologiques n'ont pas encore ete etudies adequatement dans des preparations de coeur isole. A l'aide de la technique de microelectrode classique et de la technique de << patch-clamp >> avec configuration sur cellules entieres, nous avons etudie les effets de l'ibuprofene sur les caracteristiques du potentiel d'action ainsi que sur plusieurs courants ioniques transmembranaires dans des preparations de coeur et de myocytes ventriculaires isoles enzymatiquement. Dans le muscle papillaire de chien (200 [micro]M; n = 6) et de lapin (100 [micro]M; n = 7) stimule a une frequence de 1 Hz, l'ibuprofene entrainait une prolongation de la repolarisation notable, bien que moderee. Dans les fibres de Purkinje canines, la duree et la vitesse maximale de la repolarisation diminuaient de maniere frequence-dependante. Chez le lapin (n = 7), la levofloxacine (40 [micro]M) administree seule n'entrainait pas de modification de la repolarisation, mais bien une augmentation du prolongement de la repolarisation obtenu avec l'ibuprofene. Dans les myocytes canins, l'ibuprofene (250 [micro]M) n'avait pas d'influence marquee sur [I.sub.K1], mais entrainait une diminution de l'amplitude des courants potassiques Ito et [I.sub.Kr] de 28,2 (60 mV) et de 15,2 % (20 mV), respectivement. L'ibuprofene entrainait aussi une depression des courants [I.sub.NaL] et [I.sub.Ca] de 19,9 et de 16,4 %, respectivement. Nous en arrivons a la conclusion que l'ibuprofene ne semble pas avoir d'effet sur les parametres du potentiel d'action a de faibles concentrations. Cependant, a des concentrations plus elevees, il pourrait porter atteinte a la reserve de repolarisation, participant ainsi au risque proarythmique observe chez les patients. [Traduit par la Redaction] Mots-cles : ibuprofene, levofloxacine, reserve de repolarisation., Introduction Ibuprofen is one of the most widely used nonsteroidal antiinflammatory drugs (NSAIDs) (Rainsford 2009). However, a recent Danish nationwide case-time-control study (Sondergaard et al. 2017) found that short-term therapy [...]

Cardiovascular diseases are the leading causes of mortality. Sudden cardiac death is most commonly caused by ventricular fibrillation (VF). Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and a major cause of stroke and heart failure. Pharmacological management of VF and AF remains suboptimal due to limited efficacy of antiarrhythmic drugs and their ventricular proarrhythmic adverse effects. In this study, the antiarrhythmic and cardiac cellular electrophysiological effects of SZV-270, a novel compound, were investigated in rabbit and canine models. SZV-270 significantly reduced the incidence of VF in rabbits subjected to coronary artery occlusion/reperfusion and reduced the incidence of burst-induced AF in a tachypaced conscious canine model of AF. SZV-270 prolonged the frequency-corrected QT interval, lengthened action potential duration and effective refractory period in ventricular and atrial preparations, blocked [I.sub.Kr] in isolated cardiomyocytes (Class III effects), and reduced the maximum rate of depolarization ([V.sub.max]) at cycle lengths smaller than 1000 ms in ventricular preparations (Class I/B effect). Importantly, SZV-270 did not provoke Torsades de Pointes arrhythmia in an anesthetized rabbit proarrhythmia model characterized by impaired repolarization reserve. In conclusion, SZV-270 with its combined Class I/B and III effects can prevent reentry arrhythmias with reduced risk of provoking drug-induced Torsades de Pointes. Key words: action potential duration, atrial fibrillation, combined Class I/B and Class III effects, ventricular fibrillation, Torsades de Pointes. Les maladies cardiovasculaires sont les premieres causes de mortalite. La mort subite cardiaque est le plus souvent causee par une fibrillation ventriculaire (FV). La fibrillation auriculaire (FA) est la plus frequente cause d'arythmie cardiaque et une des plus importantes causes d'AVC et d'insuffisance cardiaque. La prise en charge pharmacologique de la FV et de la FA demeure suboptimale en raison de l'efficacite limitee des medicaments antiarythmiques, ainsi que de leurs effets indesirables proarythmiques sur les ventricules. Cette etude portait sur les effets antiarythmiques et sur l'electrophysiologie cardiaque cellulaire du SZV-270, un nouveau compose, dans des modeles chez le lapin et le chien. Le SZV-270 entrainait une diminution marquee de la frequence d'apparition de la FV chez des lapins apres l'occlusion d'une artere coronaire suivie d'une reperfusion, ainsi que de la FA induite par salves de stimulations dans un modele de FA chez le chien conscient avec pacing rapide. Le SZV-270 entrainait un prolongement de l'intervalle QT corrige pour la frequence, de la duree du potentiel d'action et de la periode refractaire effective dans des preparations de ventricule et d'auricule, ainsi qu'une inhibition du courant [I.sub.Kr] dans des cardiomyocytes isoles (effet de classe III). Il entrainait aussi une diminution de la vitesse maximale de la depolarisation ([V.sub.max]) a des durees de cycle inferieures a 1000 ms dans des preparations de ventricule (effet de classe I/B). Il est important de noter que le SZV-270 n'entrainait pas de torsades de pointes dans un modele de proarythmie chez le lapin anesthesie caracterise par une reserve de repolarisation diminuee. En conclusion, avec ses effets de classe I/b et de classe III combines, le SZV-270 peut permettre de prevenir les arythmies par reentree avec une decroissance du risque de provoquer des torsades de pointes induites par les medicaments. [Traduit par la Redaction] Mots-cles : duree du potentiel d'action, fibrillation auriculaire, effets de classe I/B et de classe III combines, fibrillation ventriculaire, torsades de pointes., Introduction Cardiovascular diseases remain the leading causes of mortality in the developed world. Approximately 18 million lives are lost annually due to sudden cardiac death, most commonly caused by severe [...]

The present study was designed to test the hypothesis that the selectivity of blocking the late Na+ current (INaL) over the peak Na+ current (INaP) is related to the fast offset kinetics of the Na+ channel inhibitor. Therefore, the effects of 1 µM GS967 (INaL inhibitor), 20 µM mexiletine (I/B antiarrhythmic) and 10 µM quinidine (I/A antiarrhythmic) on INaL and INaP were compared in canine ventricular myocardium. INaP was estimated as the maximum velocity of action potential upstroke (V+max). Equal amounts of INaL were dissected by the applied drug concentrations under APVC conditions. The inhibition of INaL by mexiletine and quinidine was comparable under a conventional voltage clamp, while both were smaller than the inhibitory effect of GS967. Under steady-state conditions, the V+max block at the physiological cycle length of 700 ms was 2.3% for GS967, 11.4% for mexiletine and 26.2% for quinidine. The respective offset time constants were 110 ± 6 ms, 456 ± 284 ms and 7.2 ± 0.9 s. These results reveal an inverse relationship between the offset time constant and the selectivity of INaL over INaP inhibition without any influence of the onset rate constant. It is concluded that the selective inhibition of INaL over INaP is related to the fast offset kinetics of the Na+ channel inhibitor. [ABSTRACT FROM AUTHOR]

A substantial body of evidence indicates that pharmacological activation of mitochondrial ATP-sensitive potassium channels (m[K.sub.ATP]) in the heart is protective in conditions associated with ischemia/reperfusion injury. Several mechanisms have been postulated to be responsible for cardioprotection, including the modulation of mitochondrial respiratory function. The aim of the present study was to characterize the dose-dependent effects of novel synthetic benzopyran analogues, derived from a BMS-191095, a selective m[K.sub.ATP] opener, on mitochondrial respiration and reactive oxygen species (ROS) production in isolated rat heart mitochondria. Mitochondrial respiratory function was assessed by high-resolution respirometry, and [H.sub.2][O.sub.2] production was measured by the Amplex Red fluorescence assay. Four compounds, namely KL-1487, KL-1492, KL-1495, and KL-1507, applied in increasing concentrations (50, 75, 100, and 150 µmol/L, respectively) were investigated. When added in the last two concentrations, all compounds significantly increased State 2 and 4 respiratory rates, an effect that was not abolished by 5-hydroxydecanoate (5-HD, 100 µmol/L), the classic m[K.sub.ATP] inhibitor. The highest concentration also elicited an important decrease of the oxidative phosphorylation in a [K.sup.+] independent manner. Both concentrations of 100 and 150 µmol/L for KL-1487, KL-1492, and KL-1495, and the concentration of 150 µmol/L for KL-1507, respectively, mitigated the mitochondrial [H.sub.2][O.sub.2] release. In isolated rat heart mitochondria, the novel benzopyran analogues act as protonophoric uncouplers of oxidative phosphorylation and decrease the generation of reactive oxygen species in a dose-dependent manner. Key words: rat heart mitochondria, benzopyran analogues, protonophores, uncoupling, hydrogen peroxide. De plus en plus de donnees indiquent que l'activation pharmacologique des canaux potassiques sensibles a l'ATP de la mitochondrie (m[K.sub.ATP]) du coeur le protege lorsqu'il est expose a des conditions associees au dommage d'ischemie/reperfusion. Plusieurs mecanismes pourraient etre responsables de la cardioprotection incluant la modulation de la fonction respiratoire mitochondriale. Le but de l'etude presente etait de caracteriser les effets lies a la dose de nouveaux analogues synthetiques du benzopyrane, derives du BMS-191095, un compose qui ouvre selectivement les m[K.sub.ATP], sur la respiration mitochondriale et la production d'especes reactives d'oxygene (ERO) dans les mitochondries isolees du coeur de rat et ce. La fonction respiratoire mitochondriale a ete evaluee par respirometrie a haute resolution et la production de [H.sub.2][O.sub.2] a ete mesuree par un dosage en fluorescence a l'aide de la trousse Amplex Red. Quatre composes, a savoir KL-1487, KL-1492, KL-1495 et KL-1507, ajoutes en concentrations croissantes (50,75,100 et 150 µmol/L, respectivement), ont ete examines. Lorsqu'ajoutes aux deux concentrations les plus elevees, tous les composes accroissaient significativement les taux respiratoires aux etats 2 et 4, effet qui n'etait pas aboli par le 5-hydroxydecanoate (5-HD, 100 µmol/L), l'inhibiteur classique des m[K.sub.ATP]. La plus forte concentration induisait aussi une diminution importante de la phosphorylation oxydative de maniere independante du [K.sup.+]. Les deux concentrations de 100 µmol/L et 150 µmol/L de KL-1487, KL-1492 et KL-1495, et la concentration de 150 µmol/L de KL-1507 diminuaient respectivement la liberation de [H.sub.2][O.sub.2] de la mitochondrie. Les nouveaux analogues du benzopyrane agissent comme decouplants protonophores de la phosphorylation oxydative dans les mitochondries isolees du coeur de rat, et diminuent la generation d'especes reactives d'oxygene en fonction de leur concentration. [Traduit par la Redaction] Mots-cles : mitochondries du coeur de rat, analogues du benzopyrane, protonophores, effet decouplant, peroxyde d'hydrogene., Introduction In the past decades mitochondria have emerged as major contributors to the pathogenesis of myocardial ischemia/reperfusion (I/R) injury as well as important therapeutic targets in cardioprotection (Camara et al. [...]

Data obtained from canine cardiac electrophysiology studies are often extrapolated to the human heart. However, it has been previously demonstrated that because of the lower density of its [K.sup.+] currents, the human ventricular action potential has a less extensive repolarization reserve. Since the relevance of canine data to the human heart has not yet been fully clarified, the aim of the present study was to determine for the first time the action potentials of undiseased human Purkinje fibres (PFs) and to compare them directly with those of dog PFs. All measurements were performed at 37°C using the conventional microelectrode technique. At a stimulation rate of 1 Hz, the plateau potential of human PFs is more positive (8.0 ± 1.8 vs 8.6 ± 3.4 mV, n = 7), while the amplitude of the spike is less pronounced. The maximal rate of depolarization is significantly lower in human PKs than in canine PFs (406.7 ± 62 vs 643 ± 36 V/s, respectively, n = 7). We assume that the appreciable difference in the protein expression profiles of the 2 species may underlie these important disparities. Therefore, caution is advised when canine PF data are extrapolated to humans, and further experiments are required to investigate the characteristics of human PF repolarization and its possible role in arrhythmogenesis. Key words: human, dog, heart, Purkinje fibre, ventricle, action potential, electrophysiology. Les donnees recueillies d'etudes en electrophysiologie cardiaque chez le chien sont souvent extrapolees a l'humain. Cependant, il a ete demontre precedemment que, en consequence de la densite plus faible de ses courants [K.sup.+], le potentiel d'action ventriculaire humain possede une reserve de repolarisation moins importante. Puisque la pertinence des donnees chez le chien au coeur humain n'a pas encore ete pleinement clarifiee, le but de l'etude presente etait d'etablir pour la premiere fois les potentiels d'action des fibres de Purkinje (FP) humaines saines et de les comparer directement a ceux du chien. Toutes les mesures ont ete realisees a 37°C a l'aide d'une methode conventionnelle par microelectrode. A un taux de stimulation de 1 Hz, le potentiel plateau des FP humaines est davantage positif (8,0 ± 1,8 vs 8,6 ± 3,4 mV, n = 7), alors que l'amplitude de la pointe est moins prononcee. Le taux maximal de depolarisation est significativement plus faible chez les FP humaines comparativement a celles du chien (406,7 ± 62 vs 643 ± 36 V/s, n = 7). Les auteurs assument que la difference appreciable des profiles d'expression proteique entre les deux especes peut sous-tendre ces disparites importantes. La prudence est ainsi de mise lorsque des donnees obtenues dans les FP de chien sont extrapolees aux humains, et des experiences plus approfondies sont requises afin d'examiner les caracteristiques de la repolarisation des FP humaines et leur role possible dans l'arythmogenese. [Traduit par la Redaction] Mots-cles: humain, chien, coeur, fibre de Purkinje, ventricule, potentiel d'action, electrophysiologie., Introduction The cardiac Purkinje fibre (PF) system plays an important role in impulse propagation and in the generation of cardiac arrhythmias (Aiello et al. 2002; Han et al. 2002a). It [...]

Loss-of-function mutations of the KCNJ2 gene encoding for the inward rectifier potassium channel subunit Kir2.1 cause Andersen-Tawil Syndrome (ATS), a rare genetic disorder characterised by periodic paralysis, ventricular arrhythmias, and dysmorphic features. Clinical manifestations of the disease appear to vary greatly with the nature of mutation, therefore, functional characterisation of ATS-causing mutations is of clinical importance. In this study, we describe the identification and functional analysis of a novel KCNJ2 mutation, Val302del, identified in a patient with ATS. Heterologously expressed wild type (WT) and Val302del mutant alleles showed similar subcellular distribution of the Kir2.1 protein with high intensity labelling from the membrane region, demonstrating normal membrane trafficking of the Val302del Kir2.1 variant. Cells transfected with the WT allele displayed a robust current with strong inward rectification, while no current above background was detected in cells expressing the Val302del Kir2.1 subunit. Co-transfection of CHO cells with the WT and the Val302del Kir2.1 revealed a dose-dependent inhibitory effect of the Val302del Kir2.1 mutant subunit on WT Kir2.1 currents. These observations indicate that the WT and the Val302del mutant subunits co-assemble in the cell membrane and that the mutation affects potassium conductivity and (or) gating of the WT/Val302del heteromeric Kir2.1 channels. Key words: Andersen-Tawil Syndrome, KCNJ2 mutation, KCNJ2 gene, inward rectifier potassium channel, Kir2.1 subunit. Les mutations associees a une perte fonctionnelle du gene KCNJ2 codant la sous-unite Kir2.1 du canal potassique a rectification entrante causent le syndrome d'Andersen-Tawil, un trouble genetique rare associe a une paralysie periodique, des arythmies ventriculaires et des caracteristiques dysmorphiques. Les manifestations cliniques de la maladie semblent varier largement selon la nature de la mutation: la caracterisation fonctionnelle des mutations responsables du syndrome d'Andersen-Tawil revet une importance clinique. Dans le cadre de ces travaux, nous decrivons l'identification et l'analyse fonctionnelle de Val302del, une nouvelle mutation du gene KCNJ2 identifiee chez un patient atteint du syndrome d'Andersen-Tawil. Les distributions infracellulaires de la proteine Kir2.1 dans des alleles de type sauvages et portant la mutation Val302del--exprimes de maniere heterologue--etaient similaires et presentaient un marquage a haute intensite de la region membranaire, ce qui montre que la variante Val302del de la proteine Kir2.1 est associee a un trafic membranaire normal. Le courant rectificateur entrant des cellules transfectees avec l'allele de type sauvage etait puissant, alors que celui des cellules exprimant la mutation Val302del de la sous-unite Kir2.1 ne depassait pas le courant de base. La cotransfection de cellules d'ovaires de hamster chinois avec le Kir2.1 de type sauvage et le Kir2.1 de type Val302del a revele un effet inhibiteur de la sous-unite mutante de Kir2.1 (Val302del), dans une mesure proportionnelle a la dose, sur les courants associes au Kir2.1 de type sauvage. Ces observations indiquent que les sous-unites de type sauvage et presentant la mutation Val302del s'assemblent dans la membrane cellulaire et que la mutation affecte la conductivite des canaux potassiques ou la fonction d'ouverture des canaux Kir2.1 heteromeriques de type sauvage/Val302del. [Traduit par la Redaction] Mots-cles: syndrome d'Andersen-Tawil, mutation du gene KCNJ2, gene KCNJ2, canal potassique rectificateur entrant, sous-unite Kir2.1., Introduction Andersen-Tawil Syndrome (ATS) is a rare and unique genetic disorder characterised by a triad of clinical manifestations: periodic paralysis, ventricular arrhythmias, and dysmorphic features that include cranial, facial, and [...]

Long QT syndrome (LQTS) is an inherited cardiac rhythm disorder associated with increased incidence of cardiac arrhythmias and sudden death. LQTS type 5 (LQT5) is caused by dominant mutant variants of KCNE1, a regulatory subunit of the voltage-gated ion channels generating the cardiac potassium current IKs. While mutant LQT5 KCNE1 variants are known to inhibit IKs amplitudes in heterologous expression systems, cardiomyocytes from a transgenic rabbit LQT5 model displayed unchanged IKs amplitudes, pointing towards the critical role of additional factors in the development of the LQT5 phenotype in vivo. In this study, we demonstrate that KCNE3, a candidate regulatory subunit of IKs channels minimizes the inhibitory effects of LQT5 KCNE1 variants on IKs amplitudes, while current deactivation is accelerated. Such changes recapitulate IKs properties observed in LQT5 transgenic rabbits. We show that KCNE3 accomplishes this by displacing the KCNE1 subunit within the IKs ion channel complex, as evidenced by a dedicated biophysical assay. These findings depict KCNE3 as an integral part of the IKs channel complex that regulates IKs function in cardiomyocytes and modifies the development of the LQT5 phenotype. [ABSTRACT FROM AUTHOR]

Dilated cardiomyopathy (DCM) is a multifactorial disease characterized by left ventricular dilation that is associated with systolic dysfunction and increased action potential duration. The Kir2.x [K.sup.+] channels (encoded by KCNJ genes) regulate the inward rectifier current ([I.sub.K1]) contributing to the final repolarization in cardiac muscle. Here, we describe the transitions in the gene expression profiles of 4 KCNJ genes from healthy or dilated cardiomyopathic human hearts. In the healthy adult ventricles, KCNJ2, KCNJ12, and KCNJ4 (Kir2.1-2.3, respectively) genes were expressed at high levels, while expression of the KCNJ14 (Kir2.4) gene was low. In DCM ventricles, the levels of Kir2.1 and Kir2.3 were upregulated, but those of Kir2.2 channels were downregulated. Additionally, the expression of the DLG1 gene coding for the synapse-associated protein 97 (SAP97) anchoring molecule exhibited a 2-fold decline with increasing age in normal hearts, and it was robustly downregulated in young DCM patients. These adaptations could offer a new aspect for the explanation of the generally observed physiological and molecular alterations found in DCM. Key words: inward rectifier potassium channels, [I.sub.K1], dilated cardiomyopathy, Kir2.x, SAP97. La cardiomyopathie dilatee (CMD) est une maladie multifactorielle caracterisee par une dilatation du ventricule gauche associee a une dysfonction systolique et a une augmentation de la duree du potentiel d'action. Les canaux potassiques Kir2.x (codes par les genes KCNJ) regulent le courant rectifiant entrant ([I.sub.KI]), contribuant a la repolarisation finale du muscle cardiaque. Nous decrivons ici la transition des profils d'expression genique de quatre KCNJ a partir du coeur d'individus normaux vers des coeurs cardiomyopathiques dilates. Les genes KCNJ2, KCNJ12 et KCNJ4 (Kir2.1-2.3) etaient exprimes a des niveaux eleves dans les coeurs non malades, alors que l'expression du gene KCNJ14 (Kir2.4) etait faible. Les niveaux de Kir2.1 et Kir2.3 etaient regules a la hausse dans la CMD mais ceux des canaux Kir2.2 etaient diminues. De plus, l'expression du gene DLG1 qui code la proteine associee au synapse SAP97, une proteine d'ancrage, etait diminuee de 2 fois en fonction de l'augmentation de l'age des individus dont le coeur est normal, et elle etait fortement diminuee chez les jeunes patients atteints de CMD. Ces adaptations pourraient offrir un constituer une nouvelle facon d'expliquer les modifications physiologiques et moleculaires generalement observees dans la CMD. [Traduit par la Redaction] Mots-cles: canaux potassiques rectifiants entrants, [I.sub.KI], cardiomyopathie dilatee, Kir2.x, SAP97., Introduction Dilated cardiomyopathy (DCM) is a myocardial disorder characterized by left ventricular dilation and systolic dysfunction often leading to progressive heart failure, arrhythmias, and premature death (Csanady et al. 1991; [...]

Activators of the slow delayed rectifier [K.sup.+] current ([I.sub.Ks]) have been suggested as promising tools for suppressing ventricular arrhythmias due to prolongation of repolarization. Recently, L-364,373 (R-L3) was nominated to activate [I.sub.Ks] in myocytes from several species; however, in some studies, it failed to activate [I.sub.Ks]. One later study suggested opposite modulating effects from the R-L3 enantiomers as a possible explanation for this discrepancy. Therefore, we analyzed the effect of the RL-3 enantiomers on [I.sub.Ks] in ventricular mammalian myocytes, by applying standard microelectrode and whole-cell patch- clamp techniques at 37°C. We synthesized 2 substances, ZS_1270B (right) and ZS_1271B (left), the 2 enantiomers of R- L3. In rabbit myocytes, ZS_1270B enhanced the [I.sub.Ks] tail current by approximately 30%, whereas ZS_1271B reduced [I.sub.Ks] tails by 45%. In guinea pig right ventricular preparations, ZS_1270B shortened [APD.sub.90] (action potential duration measured at 90% repolarization) by 12%, whereas ZS_1271B lengthened it by approximately 15%. We concluded that R-L3 enantiomers in the same concentration range indeed have opposite modulating effects on [I.sub.Ks], which may explain why the racemic drug R-L3 previously failed to activate [I.sub.Ks]. ZS_1270B is a potent [I.sub.Ks] activator, therefore, this substance is appropriate to test whether [I.sub.Ks] activators are ideal tools to suppress ventricular arrhythmias originating from prolongation of action potentials. Key words: L-364,373, slow delayed rectifier potassium current, [I.sub.Ks] activator, [I.sub.Ks] blocker, enantiomers, antiarrhythmic drugs. On a suggere que les activateurs du courant potassique rectifiant retarde lent ([I.sub.Ks]) soient des outils prometteurs pour supprimer les arythmies ventriculaires causees par la prolongation de la repolarisation. Recemment, le L-364,373 (R-L3) a ete identifie comme activateur du [I.sub.Ks] dans les myocytes de plusieurs especes ; toutefois, dans certaines etudes, il ne parvenait pas a activer le [I.sub.Ks]. Une etude ulterieure a suggere que les effets modulateurs opposes d'enantiomeres du R-L3 pourraient peut-etre expliquer cette divergence. Nous avons ainsi analyse l'effet d'enantiomeres de R-L3 sur le [I.sub.Ks] dans des myocytes ventriculaires de mammifere, en utilisant la technique standard de microelectrode et de patch clamp sur cellule entiere a 37°C. Nous avons synthetise deux substances, le ZS_1270B (droit) et le ZS_1271B (gauche), les deux enantiomeres du R-L3. Le ZS_1270B accroissait le courant [I.sub.Ks] de queue d'environ 30 % alors que le ZS_1271B reduisait les queues du [I.sub.Ks] de 45 %. Dans les preparations ventriculaires droites du cobaye, le ZS_1270B raccourcissait [l'APD.sub.90] de 12 % alors que le ZS_1271B l'allongeait inversement de 15 %. Nous avons conclu que les enantiomeres du R-L3 possedent effectivement des effets modulateurs opposes, ce qui peut expliquer pourquoi le melange racemique du medicament RL-3 ne parvenait pas a activer le [I.sub.Ks]. Le ZS_1270B est un puissant activateur du [I.sub.Ks] : consequemment, cette substance convient pour tester si les activateurs de [I.sub.Ks] sont effectivement des outils ideaux pour supprimer les arythmies ventriculaires emanant de la prolongations des potentiels d'action. [Traduit par la Redaction] Mots-cles: L-364,373, courant potassique rectifiant retarde lent, activateur du [I.sub.Ks], bloqueur du [I.sub.Ks], enantiomeres, medicaments anti-arythmiques., Introduction Action potential repolarization is an important phenomenon in the heart, where it controls action potential duration (APD) and thus affects refractoriness and conduction of electrical impulses throughout the heart. [...]

In the present study, the effect of long-term exercise training was investigated on myocardial morphological and functional remodeling and on proarrhythmic sensitivity in a rabbit athlete's heart model. New-Zealand white rabbits were trained during a 12-week long treadmill running protocol and compared with their sedentary controls. At the end of the training protocol, echocardiography, in vivo and in vitro ECG recordings, proarrhythmic sensitivity with dofetilide (nM) were performed in isolated hearts, and action potential duration (APD) measurements at different potassium concentrations (4.5 and 2 mM) were made in the isolated papillary muscles. Expression levels of the slow component of delayed rectifier potassium current and fibrosis synthesis and degradation biomarkers were quantified. Echocardiography showed a significantly dilated left ventricle in the running rabbits. ECG PQ and RR intervals were significantly longer in the exercised group (79 ± 2 vs. 69 ± 2 ms and 325 ± 11 vs. 265 ± 6 ms, p < 0.05, respectively). The in vivo heart rate variability (HRV) (SD of root mean square: 5.2 ± 1.4 ms vs. 1.4 ± 0.2 ms, p < 0.05) and Tpeak-Tend variability were higher in the running rabbits. Bradycardia disappeared in the exercised group in vitro. Dofetilide tended to increase the QTc interval in a greater extent, and significantly increased the number of arrhythmic beats in the trained animals in vitro. APD was longer in the exercised group at a low potassium level. Real-time quantitative PCR (RT-qPCR) showed significantly greater messenger RNA expression of fibrotic biomarkers in the exercised group. Increased repolarization variability and higher arrhythmia incidences, lengthened APD at a low potassium level, increased fibrotic biomarker gene expressions may indicate higher sensitivity of the rabbit "athlete's heart" to life-threatening arrhythmias. [ABSTRACT FROM AUTHOR]

Herein, a holistic investigation of the process chain of polymer foam template manufacturing for the investment casting of open‐cell metal foams and their evaluation in terms of mechanical response under compressive loading is presented. Polymer foam templates are manufactured using sucrose beads as spaceholders with a body‐centred cubic (bcc) stacking and epoxy resin as matrix material. These templates are used in a modified investment casting process to produce commercial pure open‐cell Al foams (AA 1050 A). The materials used for the polymer foam templates are suitable for the template production and the use in investment casting. The structure of the template can be exactly reproduced by investment casting and no byproducts from the pyrolysis step can be detected within the molds or the Al foams. The mechanical properties under compressive loading are comparable with high‐strength Al‐alloy foams with a structure factor of C1 of 0.60. The characteristic plastic deformation is dominated by buckling, showing a local plastic failure of the struts within cell layers. Due to a high node‐to‐strut thickness ratio, neither small defects in the microstructure nor stacking errors of the template impact this deformation behavior. [ABSTRACT FROM AUTHOR]

Magnesium silicide (Mg2Si) has many good properties and therefore shows a high application potential as thermoelectric material. Herein, the intermetallic layer growth behavior in the Mg–Si system is investigated. A process for synthesizing Mg2Si on the surface of open‐pore cellular Si structures is developed. The structure is fabricated by investment casting and followed by infiltration of magnesium. Subsequently, magnesium silicide is obtained by a two‐step heat treatment. Complete synthesis of Si to Mg2Si is achieved using a liquid–solid reaction between the liquid Mg and solid Si. The optimal heat treatment for the first step is at the eutectic temperature of 950 °C and for a duration of 120 min. The second treatment is at 1150 °C, slightly above the melting point of Mg2Si, and the remaining Si is synthesized. The resulting microstructures are analyzed using a scanning electron microscope (SEM) and energy‐dispersive spectroscopy (EDS). [ABSTRACT FROM AUTHOR]

Background and Purpose: The lack of selective sodium–calcium exchanger (NCX) inhibitors has hampered the exploration of physiological and pathophysiological roles of cardiac NCX 1.1. We aimed to discover more potent and selective drug like NCX 1.1 inhibitor. Experimental Approach A flavan series‐based pharmacophore model was constructed. Virtual screening helped us identify a novel scaffold for NCX inhibition. A distinctively different NCX 1.1 inhibitor, ORM‐11372, was discovered after lead optimization. Its potency against human and rat NCX 1.1 and selectivity against other ion channels was assessed. The cardiovascular effects of ORM‐11372 were studied in normal and infarcted rats and rabbits. Human cardiac safety was studied ex vivo using human ventricular trabeculae. Key Results: ORM‐11372 inhibited human NCX 1.1 reverse and forward currents; IC50 values were 5 and 6 nM respectively. ORM‐11372 inhibited human cardiac sodium 1.5 (INa) and hERG KV11.1 currents (IhERG) in a concentration‐dependent manner; IC50 values were 23.2 and 10.0 μM. ORM‐11372 caused no changes in action potential duration; short‐term variability and triangulation were observed for concentrations of up to 10 μM. ORM‐11372 induced positive inotropic effects of 18 ± 6% and 35 ± 8% in anaesthetized rats with myocardial infarctions and in healthy rabbits respectively; no other haemodynamic effects were observed, except improved relaxation at the lowest dose. Conclusion and Implications: ORM‐11372, a unique, novel, and potent inhibitor of human and rat NCX 1.1, is a positive inotropic compound. NCX inhibition can induce clinically relevant improvements in left ventricular contractions without affecting relaxation, heart rate, or BP, without pro‐arrhythmic risk. [ABSTRACT FROM AUTHOR]

Introduction: Re-entry is a basic mechanism of ventricular fibrillation, which can be elicited by extrasystolic activity, but the timing of an extrasystole can be critical. The action potential duration (APD) of an extrasystole depends on the proximity of the preceding beat, and the relation between its timing and its APD is called electrical restitution. The aim of the present work was to study and compare the effect of several antiarrhythmic drugs on restitution in preparations from undiseased human ventricular muscle, and other mammalian species. Methods: Action potentials were recorded in preparations obtained from rat, guinea pig, rabbit, and dog hearts; and from undiseased human donor hearts using the conventional microelectrode technique. Preparations were stimulated with different basic cycle lengths (BCLs) ranging from 300 to 5,000 ms. To study restitution, single test pulses were applied at every 20th beat while the preparation was driven at 1,000 ms BCL. Results: Marked differences were found between the animal and human preparations regarding restitution and steady-state frequency dependent curves. In human ventricular muscle, restitution kinetics were slower in preparations with large phase 1 repolarization with shorter APDs at 1000 ms BCL compared to preparations with small phase 1. Preparations having APD longer than 300 ms at 1000 ms BCL had slower restitution kinetics than those having APD shorter than 250 ms. The selective IKr inhibitors E-4031 and sotalol increased overall APD and slowed the restitution kinetics, while IKs inhibition did not influence APD and electrical restitution. Mexiletine and nisoldipine shortened APD, but only mexiletine slowed restitution kinetics. Discussion: Frequency dependent APD changes, including electrical restitution, were partly determined by the APD at the BCL. Small phase 1 associated with slower restitution suggests a role of Ito in restitution. APD prolonging drugs slowed restitution, while mexiletine, a known inhibitor of INa, shortened basic APD but also slowed restitution. These results indicate that although basic APD has an important role in restitution, other transmembrane currents, such as INa or Ito, can also affect restitution kinetics. This raises the possibility that ion channel modifier drugs slowing restitution kinetics may have antiarrhythmic properties by altering restitution. [ABSTRACT FROM AUTHOR]

Background and Purpose: The exact mechanism of spontaneous pacemaking is not fully understood. Recent results suggest tight cooperation between intracellular Ca2+ handling and sarcolemmal ion channels. An important player of this crosstalk is the Na+/Ca2+ exchanger (NCX), however, direct pharmacological evidence was unavailable so far because of the lack of a selective inhibitor. We investigated the role of the NCX current in pacemaking and analyzed the functional consequences of the If-NCX coupling by applying the novel selective NCX inhibitor ORM-10962 on the sinus node (SAN). Experimental Approach: Currents were measured by patch-clamp, Ca2+-transients were monitored by fluorescent optical method in rabbit SAN cells. Action potentials (AP) were recorded from rabbit SAN tissue preparations. Mechanistic computational data were obtained using the Yaniv et al. SAN model. Key Results: ORM-10962 (ORM) marginally reduced the SAN pacemaking cycle length with a marked increase in the diastolic Ca2+ level as well as the transient amplitude. The bradycardic effect of NCX inhibition was augmented when the funny-current (If) was previously inhibited and vice versa , the effect of If was augmented when the Ca2+ handling was suppressed. Conclusion and Implications: We confirmed the contribution of the NCX current to cardiac pacemaking using a novel NCX inhibitor. Our experimental and modeling data support a close cooperation between If and NCX providing an important functional consequence: these currents together establish a strong depolarization capacity providing important safety factor for stable pacemaking. Thus, after individual inhibition of If or NCX, excessive bradycardia or instability cannot be expected because each of these currents may compensate for the reduction of the other providing safe and rhythmic SAN pacemaking. [ABSTRACT FROM AUTHOR]

1. Introduction The past decade has witnessed an explosive progress of virus-based gene delivery technologies. The reason for this is that, albeit traditional approaches, such as calcium phosphate precipitation, electroporation, [...], We report the development and application of a pseudorabies virus-based system for delivery of troponeon, a fluorescent [Ca.sup.2+] sensor to adult canine cardiomyocytes. The efficacy of transduction was assessed by calculating the ratio of fluorescently labelled and nonlabelled cells in cell culture. Interaction of the virus vector with electrophysiological properties of cardiomyocytes was evaluated by the analysis of transient outward current ([I.sub.to]), kinetics of the intracellular [Ca.sup.2+] transients, and cell shortening. Functionality of transferred troponeon was verified by FRET analysis. We demonstrated that the transfer efficiency of troponeon to cultured adult cardiac myocytes was virtually 100%. We showed that even after four days neither the amplitude nor the kinetics of the [I.sub.to] current was significantly changed and no major shifts occurred in parameters of [[Ca.sup.2+].sub.i] transients. Furthermore, we demonstrated that infection of cardiomyocytes with the virus did not affect the morphology, viability, and physiological attributes of cells. Copyright [C] 2009 Janos Prorok et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The proarrhythmic potency of drugs is usually attributed to the I Kr current block. During safety pharmacology testing analysis of I Kr in cardiomyocytes was replaced by human ether-a-go-go-related gene (hERG) test using automated patch-clamp systems in stable transfected cell lines. Aim of this study was to compare the effect of proarrhythmic compounds on hERG and I Kr currents and on cardiac action potential. The hERG current was measured by using both automated and manual patch-clamp methods on HEK293 cells. The native ion currents (I Kr, I NaL, I CaL) were recorded from rabbit ventricular myocytes by manual patch-clamp technique. Action potentials in rabbit ventricular muscle and undiseased human donor hearts were studied by conventional microelectrode technique. Dofetilide, cisapride, sotalol, terfenadine, and verapamil blocked hERG channels at 37°C with an IC50 of 7 nM, 18 nM, 343 μM, 165 nM, and 214 nM, respectively. Using manual patch-clamp, the IC50 values of sotalol and terfenadine were 78 µM and 31 nM, respectively. The IC50 values calculated from I Kr measurements at 37°C were 13 nM, 26 nM, 52 μM, 54 nM, and 268 nM, respectively. Cisapride, dofetilide, and sotalol excessively lengthened, terfenadine, and verapamil did not influence the action potential duration. Terfenadine significantly inhibited I NaL and moderately I CaL, verapamil blocked only I CaL. Automated hERG assays may over/underestimate proarrhythmic risk. Manual patch-clamp has substantially higher sensitivity to certain drugs. Action potential studies are also required to analyze complex multichannel effects. Therefore, manual patch-clamp and action potential experiments should be a part of preclinical safety tests. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases remain the leading causes of morbidity and mortality worldwide. Despite recent and significant advances in our understanding of cardiovascular pathologies, the widespread clinical application of cardioprotective strategies is [...]