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Copyright of Shandong Medical Journal is the property of Shandong Medical Health Newspapers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Contemporary Pediatrics is the property of Xiangya Medical Periodical Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shandong Medical Journal is the property of Shandong Medical Health Newspapers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Diabetes Mellitus is the property of Chinese Journal of Diabetes Mellitus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Progress in Modern Biomedicine is the property of Publishing House of Progress in Modern Biomedicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shandong Medical Journal is the property of Shandong Medical Health Newspapers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Oncology is the property of Chinese Journal of Oncology / Zhonghua Zhongliu Zazhi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Progress in Modern Biomedicine is the property of Publishing House of Progress in Modern Biomedicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tianjin Medical Journal is the property of Tianjin Medical Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Progress in Modern Biomedicine is the property of Publishing House of Progress in Modern Biomedicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shandong Medical Journal is the property of Shandong Medical Health Newspapers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shandong Medical Journal is the property of Shandong Medical Health Newspapers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Basolateral inwardly-rectifying K + channels (Kir) play an important role in the control of resting membrane potential and transepithelial voltage, thereby modulating water and electrolyte transport in the distal part of nephron. Kir4.1 and Kir4.1/Kir5.1 heterotetramer are abundantly expressed in the basolateral membrane of late thick ascending limb (TAL), distal convoluted tubule (DCT), connecting tubule (CNT) and cortical collecting duct (CCD). Loss-of-function mutations in KCNJ10 cause EAST/SeSAME syndrome in humans associated with epilepsy, ataxia, sensorineural deafness and water-electrolyte metabolism imbalance, which is characterized by salt wasting, hypomagnesaemia, hypokalaemia and metabolic alkalosis. In contrast, mice lacking Kir5.1 have severe renal phenotype apart from hypokalaemia such as high chlorine metabolic acidosis and hypercalcinuria. The genetic knockout or functional inhibition of Kir4.1 suppresses Na-Cl cotransporter (NCC) expression and activity in the DCT. However, the downregulation of Kir4.1 increases epithelial Na + channel (ENaC) expression in the collecting duct. Recently, factors regulating expression and activity of Kir4.1 and Kir4.1/Kir5.1 were identified, such as cell acidification, dopamine, insulin and insulin-like growth factor-1. The involved mechanisms include PKC, PI3K, Src family protein tyrosine kinases and WNK-SPAK signal transduction pathways. Here we review the progress of renal tubule basolateral Kir, and mainly discuss the function and regulation of Kir4.1 and Kir4.1/Kir5.1.

Potassium channels have multitudinous subtypes, which are widely distributed on cell membranes. They affect various cellular physiological functions through participating in processes such as resting potential formation, substance transportation, enzyme activity and cellular communication. Autophagy is a significant mechanism to maintain intracellular metabolic homeostasis. The abnormity of autophagy may lead to the occurrence and development of multiple diseases. Recently, it has been reported that K + channels and cell autophagy are closely related. Here, we reviewed the recent research progresses on regulation of autophagy signaling, autophagy flux or autophagolysosome formation by K + channel, and discussed the physiological significance of autophagy regulation by K + channel.

In order to explore the mechanisms underlying the vasoconstriction induced by blockade of inward rectifier K + channels (K ir ) with BaCl 2 , myogenic tone of isolated rat coronary artery (RCA) was recorded with wire myograph. The dependence of BaCl 2 - induced contraction on intracellular Ca 2+ ([Ca 2+ ] i ) release and extracellular Ca 2+ ([Ca 2+ ] o ) influx was studied by Ca 2+ deprivation and restoration. The mechanisms underlying BaCl 2 -induced RCA contraction were investigated with specific inhibitors. BaCl 2 (0.1-1.0 mmol/L) contracted isolated RCA in a concentration-dependent manner and the maximal contraction was (5.69 ± 1.07) mN, nearly equal to contraction induced by 60 mmol/L KCl. The contractions induced by BaCl 2 in Ca 2+ -free solution and by followed restoration of 2.5 mmol/L Ca 2+ accounted for (35.44 ± 6.72)% and (64.56 ± 5.94)%, respectively. Calcium channel blocker nifedipine (0.3 μmol/L), cyclooxygenase inhibitor indomethacin (100 μmol/L), ERK1/2 inhibitor PD98059 (10 μmol/L) and chloride channel blocker niflumic acid (100 μmol/L) pretreatment depressed the BaCl 2 -induced maximal contraction by (87.82 ± 5.43)% (P < 0.01), (73.23 ± 5.47)% (P < 0.01), (75.69 ± 7.94)% (P < 0.01) and (83.24 ± 7.69)% (P < 0.01), respectively. These results demonstrate that BaCl 2 induces vasoconstriction in RCA by enhancing both [Ca 2+ ] i release and [Ca 2+ ] o influx, and suggest that increase of prostanoids synthesis, activation of calcium channels and chloride channels, as well as ERK1/2 pathway may be involved in this process.

We studied the effects of the lidocaine on the hERG K(+) channels with a focus on the electrophysiology of the heart. The hERG current was recorded using the conventional whole-cell patch clamp technique and the channel protein expression level was measured with Western blot in HEK 293 cells stablely expressed hERG K(+) channels. The langendorff perfusion system was used to record the ECG from isolated rabbit heart. Lidocaine inhibited hERG current in a concentration-dependent manner at 0.3-1 000 μmol·L(-1), the IC(50) value was 88.63 ±7.99 μmol·L(-1). The inhibitory action was enhanced by positive votalge without changing the votalge-dependent activation of the channel. However, lidocaine inhibited hERG current in a frequency-dependent manner. In addition, chronic incubation of lidocaine did not change the hERG K(+) channel protein expression. ECG recordings in the isolated perfused rabbit heart demonstrated that lidocaine( > 100 μmol·L(-1)) did not affected QTc interval, but decreased the heart rate and prolonged the PR interval and QRS duration. Our results demonstrate that lidocaine potentially inhibits the hERG K(+) current at a high concentration, but does not prolonged the QTc of ECG.

Objective: The purpose of this paper was to study the electrophysiological properties and the type of potassium channels on cell membrane in the stria vascularis pericytes in cochlear of guinea pig., Methods: Firstly examined the expression of the stria vascularis pericytes by desmin, a marker of pericytes, in cochlear of guinea pig with immunofluorescent method. Using whole-cell patch clamp recording techniques to observe electrophysiological properties in the cochlear pericytes in stria vascularis of guinea pig., Results: Pericytes were predominately distributed in the capillaries of cochlea.The average membrane capacitance, resistance, and potential of a single pericyte in stria vascularis were(5.9±0.3)pF, (2.2±0.3)GΩ and (-30.9±1.2)mV, respectively by using patch clamp technique. In addition, the average current density of cochlear pericyte was voltage-sensitive (Vh from 0 to + 60 mV, in 20 mV steps). The pericytes exhibited outward current and this property could be blocked by TEA (tetraethylammonium) 1 mmol/L, a large-conductance calcium-activated potassium channel(BKCa)inhibitor and 4-AP (4-aminopyridine) 1 mmol/L, a voltage-dependent K(+) channels(KV) channel blocker. TEA blocked the outward current from (296.2±35.9)pA to (163.7±16.8)pA and 4-AP blocked the outward current from (248.7±39.8)pA to (158.0±38.0)pA., Conclusion: These results suggest that pericytes in stria vascularis have BKCa and KV channels.

Erythrocytes lack nuclei and mitochondria, critical elements in the machinery of nucleated cell apoptosis. However, most recently, it became obvious that erythrocytes may undergo programmed aging, as well as suicidal death. The term eryptosis has been coined to describe the suicidal erythrocyte death. Eryptosis is triggered mainly by increased cytosolic Ca(2+) activity, in turn, Ca(2+) activates Ca(2+)-sensitive K(+) channels, scramblase, calpain and other proteases, respectively. A series of molecular events of erythrocyte programmed death induced. The cascade reaction of related molecules and finally lead to cell clearance. There is evidence suggesting that erythrocytes aging and death process are regulated tightly and there are many molecular participants and signaling pathways involved in aging and death process of erythrocytes. Erythrocytes have already been used as a model for aging study, and the knowledge about mechanisms involved in eryptosis may provide an important clue to understand the mechanisms involved in suicidal death of nucleated cells. In this review the factors influencing programmed death of erythrocytes, the role of Ca(2+) and ceramide in programmed death of erythrocytes, the role of blebbing in process of erythrocyte aging, the antigens of erythrocyte aging and so on are summarized.

The aim of the present study is to investigate the expressions of ATP-sensitive K(+) channels (KATP) in pulmonary artery smooth muscle cells (PASMCs) and the relationship with p38 MAPK signal pathway in rats. Male SD rat PASMCs were cultured in vitro, and a model of hypoxia and hypercapnia was reconstructed. PASMCs were divided to normal (N), hypoxia-hypercapnia (H), hypoxia-hypercapnia+DMSO incubation (HD), hypoxia-hypercapnia+SB203580 (inhibitor of p38 MAPK pathway) incubation (HS) and hypoxia-hypercapnia+Anisomycin (agonist of p38 MAPK pathway) incubation (HA) groups. Western blot was used to detect the protein expression of SUR2B and Kir6.1; semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the mRNA expression of SUR2B and Kir6.1. The results demonstrated that: (1) Compared with N, H, HD and HS groups, the expressions of Kir6.1 mRNA and protein in PASMCs of HA group were decreased significantly (P < 0.01), but there were no differences among N, H, HD and HS groups (P > 0.05); (2) Compared with N group, the expressions of SUR2B mRNA and protein in H, HD, HS and HA groups were increased significantly (P < 0.05), but there were no differences among H, HD, HS and HA groups (P > 0.05). The results imply that: (1) Hypoxia-hypercapnia, SB203580 didn't change the expressions of Kir6.1 mRNA and protein in PASMCs, but Anisomycin decreased the expressions of Kir6.1 mRNA and protein, so Kir6.1 may be regulated by the other subfamily of MAPK pathway; (2) Hypoxia-hypercapnia raised SUR2B mRNA and protein expressions in PASMCs, but SB203580 and Anisomycin did not affect the changes, so the increasing of SUR2B mRNA and protein induced by hypoxia-hypercapnia may be not depend on p38 MAPK pathway.

Adenylate cyclase 3 (AC3) is one of the major players in the olfactory signaling within the main olfactory epithelium (MOE) of mice. However, we are not ascertained whether deficiency of AC3 will lead to the differential expression of related genes in the MOE. Forward and reverse subtractive libraries were constructed by suppression subtractive hybridization (SSH) approach, with MOEs from AC3(-/-) and AC3(+/+) mice. These two libraries were primarily screened by Dot blot, differential expressed clones were sequenced and analyzed by bioinformatics, and differential expressed genes were verified by qRT-PCR. A total of 386 differentially expressed clones were picked out after Dot blot. The DNA sequences of 80 clones randomly selected were determined, and 62 clones were identified by blasting in GenBank. We found that 24 up-regulated clones were corresponded to genes of kcnk3, mapk7, megf11, and 38 down-regulated clones were corresponded to tmem88b, c-mip, skp1a, mlycd, etc. Their functions were annotated with Gene Ontology (GO) and found to be mainly focused on molecular binding, cell cycle, processes of biology and cells. Five genes (kcnk3, c-mip, mlycd, tmem88b and trappc5) were verified by qRT-PCR with individuals of AC3(+/+) and AC3(-/-) mice. The data indicate that kcnk3 gene is up-regulated significantly, increasing 1.27 folds compared to control mice, whereas c-mip, mlycd, tmem88b and trappc5 are down-regulated significantly, decreasing 20%, 7%, 32% and 29% compared to the AC3(+/+)mice. The functions of these genes are closely related with K(+) channels, cell differentiation, metabolism of fats, membrane transportation, and so on. It is tempting to speculate that these genes might work together with AC3 to orchestrate the olfactory transduction signaling in the MOE.

Brain growth spurt (BGS) is the critical period of neuronal growth and synaptic connection. The voltage-gated K(+) channel is the key channel for maintenance of cell excitability and information transfer among neurons. The purpose of the present study is to investigate the critical period of voltage-gated K(+) channel development in hippocampal CA1 neurons during the BGS. Changes of voltage-gated K(+) currents in neurons from acutely isolated hippocampal CA1 brain slices of rats at different ages (0-4 weeks after birth) were recorded by the whole-cell patch-clamp technique. The depolarization voltage was set at +90 mV, and 0 week was set as the control group. The experimental results showed that, with increasing ages (1-4 weeks), the maximum current densities of IA increased by (16.14 ± 0.51)%, (81.73 ± 10.71)%, (106.72 ± 5.29)%, (134.58 ± 8.81)% (n = 10, P < 0.05), and the maximum current densities of IK increased by (16.75 ± 3.88)%, (134.01 ± 2.85)%, (180.56 ± 8.49)%, (194.5 ± 8.53)% (n = 10, P < 0.05), respectively, compared with those in 0 week. During 0-4 weeks after birth, the activation kinetics of IA shifted to left, and the half activation voltages of IA were 14.67 ± 0.75, 13.46 ± 0.64, 8.39 ± 0.87, 4.60 ± 0.96, 0.54 ± 0.92 (mV, n = 10, P < 0.05), respectively; The activation kinetics of IK shifted to left and the half activation voltages of IK were 8.94 ± 0.85, 6.65 ± 0.89, 0.47 ± 1.15, -1.80 ± 0.89, -8.56 ± 1.08 (mV, n = 10, P < 0.05) respectively. The inactivation kinetics of IA also shifted to left, and the half inactivation voltages were -45.68 ± 1.26, -46.81 ± 0.78, -48.64 ± 0.81, -51.96 ± 1.02, -58.31 ± 1.35 (mV, n = 10) respectively at 0, 1, 2, 3 and 4 weeks after birth, which showed no significant changes between 0 and 1 week, but significant decreases during 1-4 weeks after birth (P < 0.05). These results indicate that the current densities of IA and IK increase and the kinetic characteristics of the voltage-gated K(+) channels change with increasing ages during 0-4 weeks after birth, and the differences are especially significant between the 1st week and the 2nd week after birth. These changes may be related to the maturation of hippocampal neurons and the progress of their functions.

The aim of the present study was to investigate the effects of acute hypoxia on the electrophysiological properties of vascular smooth muscle cells (VSMCs) in arteriole. Guinea-pig anterior inferior cerebellar artery (AICA) segments were isolated, and outer layer connective tissue was removed by collagenase A digestion and microforceps. By perfusion with physical saline solution containing no glucose and low oxygen, VSMC model of acute hypoxia was established. The model was studied by whole-cell patch clamp recording technique. Results were shown as below: (1) Acute hypoxia induced an outward current with amplitude of (36.4 ± 9.2) pA at holding potential of -40 mV, and the rest potential (RP) of the VSMCs was hyperpolarized from (-33.2 ± 1.9) mV to (-38.4 ± 1.5) mV. Acute hypoxia increased the outward current of VSMCs in a voltage-dependent manner, this enhancing effect being more pronounced at potentials ranging from 0 to +40 mV. The whole-cell membrane current of VSMCs induced by step command (+40 mV) increased from (650 ± 113) pA to (1 900 ± 197) pA. In the presence of 1 mmol/L tetraethylammonium (TEA), the enhancement of the VSMC membrane current by acute hypoxia was significantly reduced. (2) Acute hypoxia increased the membrane resistance (R(input)) of the VSMCs in AICA from (234 ± 63) MΩ to (1 211 ± 201) MΩ, and decreased the membrane capacitance (C(input)) from (279.3 ± 83.2) pF to (25.4 ± 1.9) pF. In the presence of 30 μmol/L 18β-glycyrrhetinic acid (18βGA) and 10 mmol/L TEA, the effects of acute hypoxia on the membrane current of VSMCs were nearly abolished. These results suggest that acute hypoxia causes vascular hyperpolarization and vasodilation, possibly by activating big conductance Ca(2+)-activated K(+) channels (BK(Ca)) of the VSMCs, and inhibits gap junctions between VSMCs, thus improving microcirculation and localizing the hypoxia-induced damage.

The aim of the present study was to investigate the effect of 18β-glycyrrhetinic acid (18βGA) on the membrane current of vascular smooth muscle cells (VSMCs) in arteriole. Guinea pig anterior inferior cerebellar artery (AICA) and mesenteric artery (MA) were isolated, and single VSMCs were harvested using digestion with papain and collagenase IA. Outward currents of the VSMCs were recorded by whole-cell patch clamp technique. Results were shown as below: (1) 1 mmol/L 4-AP and 1 mmol/L TEA both could partially inhibit the whole-cell current of VSMCs in arterioles. (2) 18βGA inhibited the outward current of VSMCs in a concentration-dependent manner. The inhibitory rates of 10, 30 and 100 μmol/L 18βGA on the membrane current of VSMCs (+40 mV) were (25.3 ± 7.1)%, (43.1 ± 10.4)% and (68.4 ± 3.9)% respectively in AICA, and (13.2 ± 5.6)%, (34.2 ± 4.0)% and (59.3 ± 7.3)% respectively in MA. There was no significant difference between the inhibitory effects of 18βGA on AICA and MA. 18βGA also inhibited the outward current of VSMCs in a voltage-dependent manner. 18βGA induced a more pronounced inhibition of the outward current from 0 to +40 mV, especially at +40 mV. (3) With the pretreatment of 10 mmol/L TEA, the inhibitory effect of 18βGA on the membrane current of VSMCs was significantly abolished. These results suggest that the outward current of VSMCs in arterioles is mediated by voltage-dependent K(+) channels (K(v)) and big conductance calcium-activated K(+) channels (BK(Ca)), which can be inhibited by 18βGA in concentration- and voltage-dependent way.

Objective: To observe the effects of acute hypoxia on the electrophysiological properties of vascular smooth muscle cells (VSMCs) of mesenteric artery in guinea pig., Methods: A segment of mesenteric artery (MA) (outer diameter < 100 µm) of guinea pig was digested with collagenase A and its adventitial connective tissue cleaned subsequently with fine tweezers. Whole-cell patch clamp recordings were performed to study the effects of acute hypoxia on the whole-cell membrane current, resting membrane potential (RP), membrane input capacitance (C(input)), and membrane input resistance (R(input) or its reciprocal membrane input conductance G(input)) of VSMC embedded in arteriolar segment., Results: Acute hypoxia induced an outward current with an amplitude of (76 ± 23) pA at holding potential -40 mV and hyperpolarized VSMC from a RP of (-22.5 ± 1.2) mV to (-42.0 ± 2.8) mV (P < 0.01). Acute hypoxia increased the outward current of VSMC in a voltage-dependent manner. And this enhancement was more pronounced at potentials from 0 to +40 mV. The whole-cell membrane current of VSMC induced by step commands (0, +20 and +40 mV) increased from (140 ± 18) pA to (660 ± 124) pA (P < 0.01), (282 ± 23) pA to (1120 ± 186) pA (P < 0.01) and (423 ± 40) pA to (1800 ± 275) pA (P < 0.01) respectively. In the presence of 1 mmol/L tetraethylammonium (TEA, a large conductance Ca(2+)-activated K(+) channel blocker), the enhancement of VSMC membrane current by acute hypoxia was significantly reduced. Acute hypoxia increased the R(input) of VSMC in MA from (446 ± 55) MΩ to (2187 ± 290) MΩ (P < 0.01) and decreased the C(input) from (184.3 ± 75.0) pF to (17.6 ± 2.2) pF (P < 0.01). In the presence of 30 µmol/L 18β-glycyrrhetinic acid (18βGA, a gap junction blocker) and 10 mmol/L TEA, the effects of acute hypoxia on the membrane current of VSMCs were almost abolished., Conclusion: Acute hypoxia causes vascular hyperpolarization and vasodilation by activating large conductance Ca(2+)-activated K(+) channels of VSMC and inhibits gap junctions between VSMCs so as to improve microcirculation and localize hypoxia-induced damage.

Objective: To investigate the vasorelaxation effect of crocetin (CCT) and its mechanism., Methods: Isolated aortic rings from Sprague-Dawley rats were mounted in the organ bath system. The tension of the aorta was recorded., Result: CCT significantly provoked concentration-dependent relaxation in both endothelium-intact and-denuded aortic rings pre-constricted by phenylephrine (10⁻⁵ mol/L), and the vasorelaxation in endothelium-intact aortic rings was stronger than that in endothelium-denuded ones. CCT had no significant effects on aortic rings pre-constricted with KCl (6 × 10⁻² mol/L). Pretreatment with eith L-NAME (10⁻⁴ mol/L), an inhibitor of nitric oxide synthase (NOS), or indomethacin (10⁻⁵ mol/L), an inhibitor of cyclooxygenase, for 30 min significantly attenuated the relaxation of endothelium-intact aortic rings induced by CCT. Besides, both tetraethylammonium (a Ca²(+)-activated K(+) channel inhibitor, 5 × 10⁻³ mol/L) and 4-aminopyridine (a voltage-sensitive K(+) channel inhibitor, 10⁻³ mol/L), but not the ATP-sensitive K(+) channel inhibitor glibenclamide (3 × 10⁻⁶ mol/L), significantly attenuated CCT-induced relaxation in endothelium-denuded aortic rings., Conclusion: CCT had partial endothelium-dependent relaxation in rat aortas, which may be mediated by activating the endothelial NOS-NO and cyclooxygenase-prostacyclin pathways. The endothelium-independent relaxation in rat aortas induced by CCT may be mediated by Ca²(+)-activated K(+) channels and voltage-sensitive K(+) channels.

Voltage-dependent potassium channels (Kv) are involved in proliferation and transformation in mammary epithelial cells. In previous studies, several groups have detected various potassium channels in breast cancer cells, and they assumed that potassium channels are related to the development of breast carcinoma, although the precise mechanisms are still unknown. We have previously reported that 4-aminopyridine (4-AP), one kind of potassium channel (K(+) channel) blocker, could affect the proliferation of MCF10A cells. The aim of the present study is to explore the expression and properties of K(+) channels in human mammary epithelial cells (MCF10A) and whether Kv channels are required for the proliferation of MCF10A cell. Electrophysiological, MTT analysis, PCR and Western blot methods were used to identify a K(+) conductance which is involved in tumorigenesis and not yet be described in MCF10A cells. A voltage-dependent, outward rectification and 4-AP-sensitive K(+) current was observed in these cells. The perfusion of 5 mmol/L 4-AP significantly decreased the amplitude of Kv current from (912.5+/-0.6) pA to (275+/-0.8) pA (n=5, P<0.01), when cells were recorded using 800 ms voltage steps from a holding potential of -60 mV to voltage ranging from -60 mV to +60 mV. PCR analysis demonstrated that Kv1.1, Kv1.2, Kv1.3, and Kv1.5 were all expressed in MCF10A and MCF7 cells. Furthermore, the expression of Kv1.5 was much higher in MCF10A than that in MCF7. Inhibitory effect of 4-AP on cell proliferation was dosage-dependent. Incubation with 5 mmol/L 4-AP reduced MCF10A cell proliferation to 25.29% in 48 h. Western blot analysis showed the activation of ERK1/2 which related to cell proliferation was enhanced, while p38 activation was decreased by 4-AP treatment for 10 min. These data provided the first evidence of the Kv channels expression in MCF10A cell and 4-AP could inhibit the proliferation of MCF10A through blocking the potassium channels, and the mechanism may be related to regulating the activity of different members of cell proliferation signaling pathway of MEK/ERK.

Objective: To study the influence of 4-aminopyridine (4-AP) on proliferation, production, and apoptosis through inhibiting voltage-gated K(+) channel (Kv) in ovarian luteinized granulosa cells., Methods: Ovarian luteinized granulosa cells were recovered from 25 women with regular menses who underwent in vitro fertilization programme. The cultured granulosa cells were divided into 4 groups:blank group, 4-AP treated group, human chorionic gonadotropin (hCG)-induced group and hCG + 4-AP co-treated group. The final concentrations of hCG and 4-AP were 1250 U/L and 5 nmol/L respectively. The progesterone production was detected by the chemoluminescence method. The expression of Kv mRNA on human ovarian luteinized granulosa cell was detected by RT-PCR. The influence on the early apoptosis of granulosa cells by 4-AP was observed by flow cytometry. Cellular caspase-3 activities were observed with colorimetric method and the inhibition of the cell proliferation was studied using methyl thiazolyl tetrazolium (MTT) method., Results: (1) Kv mRNA was expressed in granulosa cell. (2) The progesterone production of the blank group, 4-AP treated group, hCG-induced group and hCG + 4-AP co-treated group were (547 +/- 64), (206 +/- 32), (1991 +/- 172) and (763 +/- 79) nmol/L, respectively after 24 hours culture. Exposure of the granulosa cells to 4-AP reduced the production of progesterone in blank and hCG-induced granulosa cells. (3) The flow cytometry analysis and the cellular caspase-3 A(405) showed that 4-AP increased the percentage of early phase apoptosis (P < 0.01): 4-AP treated group vs blank group [(40 +/- 5)% and 0.049 +/- 0.009] vs [(17 +/- 4)% and 0.029 +/- 0.008], hCG + 4-AP co-treated group vs hCG-induced group [(25 +/- 4)% and 0.039 +/- 0.008] vs [(15 +/- 3)% and 0.022 +/- 0.007]. (4) 24 hours after treated with 4-AP and hCG, the inhibitory rate of cultured granulosa cells of 4-AP treated group was higher than the blank group (19.7% vs 0), and that of hCG + 4-AP co-treated group was obviously higher than hCG-induced group (34.6% vs 0, P < 0.01)., Conclusions: The voltage-gated K(+) channels expressed by ovarian luteinized granulosa cell play an important role in cell proliferation, production, and apoptosis. 4-AP may inhibit differentiation of progesterone in granulosa cells through the inhibition of proliferation and induction of apoptosis.

Objective: To study the inhibition of cell proliferation by 4-aminopyridine (4-AP) in the human ovarian cancer cell SKOV3., Methods: The expression of voltage-gated K(+) channel on the SKOV3 cell line was detected by reverse transcription polymerase chain reaction. Inhibition of voltage-gated K(+) current by 4-AP through the whole-cell patch-clamp technique on SKOV3 cell line was recorded. The influence on the cell-cycle of the SKOV3 cell line by 4-AP was observed by flow cytometry and the inhibition of the cell proliferation was studied using methyl thiazolyl tetrazolium (MTT) method., Results: Voltage-gated K(+) channel was expressed in SKOV3 cell. Exposure of the SKOV3 cell to 5 mmol/L 4-AP reduced K(+) current by 52.5%. The 4-AP at 5 mmol/L significantly effected the progression of cell cycle with a 72 h treatment of SKOV3 cell. Exponentially growing cells without inhibitors had a distribution of 39.7% in G(0)/G(1) phase, 57.3% in S phase, and 3.0% in G(2)/M phase. In 4-AP-treated cells, the proportion of G(0)/G(1) cells increased significantly to 62.3% (P < 0.05), while there was a significant decrease in S phase cells (36.2%, P < 0.05) and G(2)/M phase (1.4%, P < 0.05). Incubation of the SKOV3 cells with 0.1, 1, 5, 10, 15, 20 mmol/L 4-AP resulted in a concentration-dependent reduction in the number of viable cells as compared with the control, and the inhibition rate was 17.5%, 35.0%, 54.6%, 69.1%, 71.2%, 72.8% respectively (vs control, P < 0.01)., Conclusion: The voltage-gated K(+) channels expressed by SKOV3 play an important role in SKOV3 cell proliferation.

The fact that the fruit and bark of plant belonging to family Melia could be used as digestive tract-parasiticide and agricultural insecticide was recorded about two thousand years ago in ancient China. Toosendanin (TSN, C30H38O11, FW=574), a triterpenoid derivative, was extracted from the bark of Melia toosendan Sieb. et Zucc. by Chinese scientists in 1950os and used as an ascarifuge in China instead of imported sendanin. Studies have demonstrated that TSN possesses special biological actions as well as considerable various values in scientific research, clinic medicine and agriculture. The first is that by interfering with neurotransmitter release by causing an initial facilitation, TSN eventually blocks synaptic transmission at both the neuromuscular junction and central synapses. The action might result from TSN-induced Ca(2+)-sensitivity change and final elimination of transmitter release machinery. The second is that despite sharing many similar actions with botulinum neurotoxin (BoNT) on blocking neuromuscular transmission, TSN has a markedly antibotulismic action in vivo and in vitro: TSN-treatment saves the botulism mice or monkeys from death; TSN-incubation in vitro or TSN-injection in vivo endows neuromuscular junction with a high tolerance to BoNT. Studies suggest that the antibotulismic action is achieved by preventing BoNT from approaching its enzymatic substrate, SNARE protein. The third, in recent years, it is also observed that TSN can induce differentiation and apoptosis in several cell lines, and suppress proliferation of various human cancer cells. The TSN-induced differentiation is Ca(2+)-dependent and the mitochondria-dependent apoptosis pathway is involved in the TSN-induced apoptosis. The fourth is that TSN inhibits various K(+) channels and selectively facilitates Ca(2+) current through L-type Ca(2+) channels and hence elevates [Ca(2+)](i). The TSN-induced [Ca(2+)](i) increase and overload could be responsible for the TSN-induced biphasic effect on neurotransmitter release, cell differentiation, apoptosis as well as the cytotoxicity of TSN.

Objective: To establish a rapid and economic method for isolating human peripheral blood eosinophils with high viability for patch-clamp studies and investigate the electrophysiological properties of Ca(2+)-activated K(+) channel of the isolated cells., Methods: Peripheral blood eosinophils were isolated by modified discontinuous Percoll density gradient centrifugation, and the electric currents in the single Ca(2+)-activated K(+) channels of the cells were recorded using patch-clamp technique with cell-attached configuration., Results: The purity of the eosinophils from healthy donors reached (90.5+/-1.6)%, with a viability rate over 99% and recovery rate of (48.2+/-6.9)%. The isolated cells were morphologically intact, from which Ca(2+)-activated K(+) channel activity could be detected., Conclusion: The peripheral blood eosinophils isolated using this rapid, simple and highly efficient method are characterized by high purity and viability without obvious cellular injuries, which are ideal for patch-clamp studies.

Aim: To investigate the role and mechanism of endothelium-derived hyperpolarizing factor (EDHF) in shear stress induced vasorelaxation of rat mesenteric artery., Methods: The changes in vessel diameter in response to variable flow (0-300 microL.min(-1)) were continuously examined. The contribution of prostacyclin (PGI2), NO and EDHF to shear stress induced relaxation were analyzed by inhibitory effects of indomethacin, N(G)-nitro-L-arginine (L-NA) and KCl. The nature and hyperpolarizing mechanism of EDHF were examined by the inhibitory effects of inhibitors of cytochrome P450 pathway and of various K+ channels., Results: The shear stress-induced relaxation were endothelium dependent and the contribution of NO was more prominent in large mesenteric arteries (400-500 microm) than that in resistance arteries (150-250 microm), whereas that of EDHF was noted in both-sized blood vessels. Tetrabutylammonium (a nonselective inhibitor of K channels) almost abolished, whereas the combination of charybdotoxin (an inhibitor of both large and intermediate-conductance Ca2+-activated K channels) and apamin (an inhibitor of small-conductance Ca2+-activated K channels) significantly inhibited the EDHF-mediated component of the shear stress-induced relaxations., Conclusion: EDHF plays an important role in shear stress-induced endothelium-dependent relaxations, and K channels especially calcium-activated K channels appear to be involved.

To study the modulatory effect of extracellular calcium on the whole cell K(+) currents (I(K)) in isolated Deiters cells, the whole cell K(+) currents were recorded when Deiters cells bathed in normal physiological solutions and calcium-free saline, respectively. The electrophysiological characteristics of I(K) currents were then analyzed with the patch clamp technique. Removing extracellular calcium significantly enhanced the amplitude of the I(K) currents, which increased by 70.2% at +50 mV test pulse. The chord conductance, measured at -30 mV test pulse, also significantly increased from (3.31-/+3.08) ns (n=42) in the normal solutions to (10.81-/+6.01) ns (n=42) in the calcium-free solutions, whereas, the zero current potential of the I(K) currents remained unchanged. In calcium-free solutions, the reversal potential of the I(K) currents was shifted to the direction of hyperpolarization, which was very close to the equilibrium K(+) potential based on the Nernst equation. In addition, both the steady state activation curve and the half activation potential, with the averaged value at (-10.13-/+5.64) mV (n=42), were shifted to the negative. However, the tendency for activation (slope conductances) was the same as that in the normal solutions. Interestingly, both the I-V and the G-V functions deduced from the calcium-inhibited K(+) currents in Deiters cells were "S" shape, implying that at least two different kinds of K(+) conductance were involved in this calcium-inhibited K(+) currents. In summary, we hypothesize that there are two mechanisms for this modulation: one is that the I(K) channels in Deiters cells containing a specific calcium sensitive domain, by which extracellular calcium modulates the structure of the K(+) channels and then the I(K) currents; the other is a novel double gated K(+) channel or an ionotropic receptor coupled to K(+) channels or a new subtype of outward K(+) channels. Removing extracellular calcium activates this novel conductance and then modulates the I(K) currents. These results indicate that a decrease in extracellular calcium not only facilitates the efflux of K(+) out of Deiters cells but also accelerates the repolorization by enhancing the I(K) currents, which in turn can effectively buffer the K(+) concentration around the outer hair cells and maintain the resting membrane potential of Deiters cells.

Objective: To study regulation of Ca(2+)-activated K(+) channels (KCa) of mesenteric artery smooth muscle cell (SMC) from 21 old patients with essential hypertension (EH) by endothelin-1 (ET-1) and prostagl E(1) (PGE(1))., Methods: Mesenteric artery branch from EH was digested by enzyme. Patch clamp technique was used to pull cell-attached and inside-out patches on mesenteric artery SMC from EH and the normotensive patients respectively. The signal channel open probability (Po), open dwell-time (To) and close dwell-time (Tc), open channel number per patch were recorded. After adding Ca(2+) (10(-8) approximately 10(-6) mol/L), ET-1(2 approximately 8 x 10(9) mol/L) and PGE(1) (10, 20, 40, 100, 200, 400 nmol/L) to cytoplasm respectively. The parameters above were observed again., Results: Compared to that of normotensive patients, the activities of KCa channels of patients with EH was higher. After adding Ca(2+) to cytoplasm,the Po of KCa channels in normotensive patients increased significantly. But it was few changes in EH group. KCa channels has dual reaction to ET-1 in normotensive patients. We have found no statistics difference when ET-1 present on KCa channels of EH cases. Whereas PGE(1) can affect KCa channels current and channels kinetic significantly in side-out patches. The Po of KCa channels increased. The To protracted and the Tc curtailed in EH., Conclusions: The activities of KCa channels of patients with EH increased significantly. but the sensitive to Ca(2+) decreased. ET-1 were few effect to KCa channels. The PGE(1) can activated KCa channels of patients with EH.

Objective: To investigate the effect of levcromakalim and cromakalim on ATP-sensitive K(+) channel (K(ATP)) and mean pulmonary arterial pressure (mPAP) in rats with chronic hypoxic pulmonary hypertension., Methods: Ninety Wistar rats were divided randomly into a normal group (15) and a chronic hypoxia group (75). Rats in the hypoxia group were exposed to hypoxia (FiO(2) = 0.10 +/- 0.05) for 3 weeks, whereas rats in the normal group maintained in air. The currents of K(ATP) of pulmonary artery smooth muscle cells (PASMCs) from both the chronic hypoxic and the normal groups were observed using patch-clamp technique inside-out configuration, and the effect of levcromakalim and cromakalim on K(ATP) from chronic hypoxic group was determined under normoxic conditions. The mPAP and mSAP were determined by catheterization in hypoxic rats before and after levcromakalim and cromakalim were administrated respectively to the rats with doses ranging from 100 micro g/kg to 200 micro g/kg intravenously., Results: Chronic hypoxia had little effect on the activity of K(ATP) in the chronic hypoxic rats. Levcromakalim and cromakalim remarkably activated the K(ATP) in chronic hypoxic rats. A dose-dependent decreasing effect on mPAP was elicited by levcromakalim and cromakalim in the hypoxic rats., Conclusion: Although K(ATP) activity is probably not directly involved in the development of chronic hypoxic pulmonary hypertension in rats, both levcromakalim and cromakalim decrease the increased mPAP induced by chronic hypoxia by activating K(ATP) of SMCs from pulmonary arteries, therefore diminishing the inhibitory effect of hypoxia on other K(+) channels.

By electrophysiological methods, cultured Drosophila embryonic and larval central neurons have been widely used to study ion channels, neurotransmitter release and intracellular message regulation. Voltage-activated K(+) channels play a crucial role in repolarizing the membrane following action potentials, stabilizing membrane potentials and shaping firing patterns of cells. In this study, a mechanical vibration-isolation system was used to produce a sufficient number of acutely dissociated larval central neurons, of which the majority were type II neurons (2~5 microm in diameter). Using patch clamp technique, the whole-cell K(+) currents in type II neurons were characterized by containing a transient 4-AP-sensitive current (I(A)) and a more slowly inactivating, TEA-sensitive component (I(K)). According to their kinetic properties, five types of whole-cell K(+) currents were identified. Type A current exhibited primarily fast transient K(+) currents that activated and inactivated rapidly. The majority of the neurons, however, slowly inactivated K(+) currents with variable inactivation time course (type B current). Type C current, being present in a small number of the cells, was mainly composed of noninactivating components. Some of the neurons expressed both transient and slow inactivating components, but the slowly inactivating components could reach more than 50% of the peak current (type D current). Type E current showed distinct voltage-dependent activation properties, characterized by its bell-shaped activation curve. Type E current was inhibited by application of Ca(2+)-free solution or 0.1 mmol/L Cd(2+). Moreover, this novel current ran down much more rapidly than other types. These results indicate that different K(+) channels, which have different kinetic and pharmacological properties, underlie the whole-cell K(+) currents in type II neurons of Drosophila larval central nervous system.

Objective: To study the inhibition of voltage-activated K(+) conductance and cell proliferation by 4-aminopyridine (4-AP) in the human small-cell lung cancer (SCLC)., Methods: Inhibition of voltage-activated K(+) current by 4-AP through the whole-cell patch-clamp technique in SCLC cell line was studied. The influence on the cell-cycle by 4-AP was observed by flow cytometry to identify the in vitro inhibition by 4-AP to the cell proliferation of the SCLC cell line., Results: Exposure of the tumor cells to 5 mmol/L 4-AP reduced the peak outward K(+) current (evoked by a depolarization to +80 mV) from 1.22 +/- 0.11 nA (n = 30) to 0.59 +/- 0.10 nA (n = 28). Flow cytometry results showed that cell population accumulated in the G(0)/G(1) phase and a significantly reduced proportion in the S phase and G(1)/G(2) phase cells after having been exposed to 4-AP for three days. Incubation of the SCLC cells with 0.1, 5, 10, 15, 20 mmol/L 4-AP resulted in a concentration-and time-dependent reduction in the number of viable cells as compared with the control., Conclusion: The voltage-activated K(+) channels expressed by SCLC play an important role in SCLC cell proliferation. The proliferation of the SCLC cells is inhibited by K(+) channel antagonists.

The purpose of this study was to investigate the effects of calcitonin gene-related peptide (CGRP) on the repolarization process in isolated guinea-pig atrial cells and to determine the contribution of K(+) channels to the CGRP-induced changes in action potential using conventional microelectrode method at the physiological temperature. We found that: (1) CGRP (16 nmol/L) antagonized the influences of potassium channel blockers, 4-AP and BaCl2, on action potential; (2) CGRP (16 nmol/L) increased the amplitude and maximum depolarizing velocity of slow action potential and shortened the conducting time in guinea pig atrial myocardium at extracellular K(+) concentration of 18.5 mmol/L; (3) CGRP (16 nmol/L) alleviated triggered activity induced by superfusion with solution containing CsCl and no potassium ion; and (4) the effects of CGRP on the configuration of action potential were temperature-dependent. At the temperature of 36.5+/-0.5 degrees C, CGRP (5, 16, and 50 nmol/L) increased the amplitude of the action potential and shortened APD(20), APD(50) and APD(90). The CGRP effects on APD(20) and APD(50) were dose-dependent and reversible. On the contrary, CGRP prolonged APD(20), APD(50) and APD(90) at the temperature of 25.5+/-2.1 degrees C. The present study suggests that CGRP possesses multiple effects on various ionic channels. Among them the effects on potassium currents are major determinants in the changes in action potential induced by CGRP under physiological temperature. It is necessary to further study the influences of CGRP on different types of potassium channels.

Using perforated and cell-attached patch clamp techniques, the characteristics of ATP sensitive K(+) channels (K(ATP)), delayed rectifier K(+) channels (K(DR)), Ca(2+) and Na+ channels on single rat pancreatic beta cell membranes were studied. The results showed that (1) the efflux and influx conductance of K(ATP) channels was about 31 and 65 pS respectively, and the reversal potential of K(ATP) was about 60 mV; (2) K(DR) was activated completely after a latency of 20 ms, and K(DR) was about 1/3 of K(ATP); (3) whole cell Ca(2+) current reached a peak (40 60 pA) at 0 mV; L-type Ca(2+) channel was the main Ca(2+) channel in beta cells, but other types of high voltage activated Ca(2+) channels existed as well; and 4) whole cell Na(+) current reached a peak (200 400 pA) at 10 mV; but the expression level of Na(+) channel in beta cells varied among the cells. About half of the beta cells virtually had no Na(+) currents.

The effects of glutamate on the transient outward potassium current of dissociated hippocampal CA(1) neurons of 7-10 d rats were studied by the whole-cell patch clamp technique. It was found that glutamate could block the transient potassium current in a dose- and time-dependent manner. The effect was partly voltage-dependent. These results suggest that glutamate may decrease the membrane conductance of K(+) channels in hippocampal neurons.

The effect of various potassium-channel blockers, 4-aminopyridine (4-AP), tetraethylammonium (TEA) and quinine, on the endocochlear potential (EP) was studied in perfused guinea pig inner ears. The fast K(+)-channel blocker, 4-AP, did not alter EP but changed its response model to intense noise exposure. While TEA and quinine significantly reduced the amplitude of negative component of EP (N-EP), comparing with a relatively smaller increase in general EP (G-EP). The results indicated the existence of different K(+)-channels with different physiological functions.

Intracellular recordings were made from 79 neurones in the mesencephalic nucleus of fifth nerve (MNV) contained within rat brain stem slice preparation in vitro. The electrical membrane characteristics of 20 neurones among them were measured. The resting membrane potential, input resistance and membrane time constant of MNV neurones were -60.3 +/- 5.6 mV, 10.5 +/- 5.4M omega and 1.3 +/- 0.5 ms respectively. No action potential occurred spontaneously at resting membrane potential. The action potential was elicited by application of a depolarizing rectangular pulse to the neuron. The data of 32 MNV neurones action potentials showed that the threshold potentials ranged from -50 mV to -55 mV, the duration of the spike was 0.8 +/- 0.2 ms and the amplitude of the spike was 69.5 +/- 6.1 mV with an overshoot of 11.9 +/- 3.6 mV. The action potential disappeared reversibly by perfusion of Na-free solution or TTX (0.3 mumol/L) added in Krebs solution. The repetitive discharge was elicited by a long lasting depolarizing rectangular pulse applied to the neuron, its frequency was 200-250 Hz at the beginning of the pulse and disappeared before the ending of the pulse. The repetitive discharge usually consists of 2-15 spikes. The halfway disappearance of the repetitive discharge was prevented by TEA or 4-AP. The subthreshold potential oscillation followed the action potential at membrane potential -60(-)-55 mV, and this potential oscillation was not affected by TTX, but it was abolished by perfusion of Ca-free solution. However, its amplitude was increased by TEA or 4-AP. When the resting membrane potential was depolarized, the outward rectification in 40 among 45 MNV neurones was seen, which was inhibited by TEA, 4-AP or Ca-free perfusion. On the other hand, the inward rectification was seen when the resting membrane potential was hyperpolarized, which was inhibited by Cs ion or Na-free perfusion. When the blockers of K channels were added into Krebs solution, the steady state I-V relationship of the neurones was changed correspondingly. It is suggested that the IDR, IA, IK(Ca), and IQ are related to the resting membrane conductances.