摘要
The purpose of the present study was to further study the characteristics and regulation of spontaneous transient outward currents(STOCs)in freshly isolated porcine coronary artery smooth muscle cells(ASMCs).STOCs were recorded using the perforated whole-cell patch-clamp configuration.STOCs were voltage-dependent and superimposed stochastically onto whole-cell Ca^(2+)-activated-K+(BKCa)currents.Charybdotoxin(ChTX,200 nmol/L),a selective blocker of BKCa channels,completely inhibited STOCs within 10 min.STOCs activity was greatly suppressed when extracellular Ca^(2+)concentration decreased from 1.8 mmol/L to 200 nmol/L,further removal of Ca^(2+)abolished STOCs activity.Ca^(2+)ionophore A23187(10μmol/L)increased STOCs activity significantly.Verapamil(20μmol/L)and CdCl2(200μmol/L),two kinds of organic L-type voltage-dependent Ca^(2+)channels(L-VDCCs)antagonists,had little effect on STOCs.In addition,the ryanodine receptors(RyRs)agonist caffeine(5 mmol/L)significantly activated STOCs.Application of ryanodine(50μmol/L)to block RyRs abolished STOCs,subsequent washout of ryanodine or application of caffeine failed to reproduce STOCs activity.Inhibition of inositol 1,4,5-trisphosphate receptors(IP_(3)Rs)by 2APB(40μmol/L)greatly suppressed the activity of STOCs,application of caffeine(5 mmol/L)in the presence of 2APB caused a burst of outward currents followed by inhibition of STOCs.These results suggest that STOCs in porcine coronary ASMCs are mediated by BKCa channels.Extracellular Ca^(2+)is essential for STOCs activity,while Ca^(2+)entry through L-VDCCs has little effect on STOCs.Intracellular Ca^(2+)release induced by RyRs is responsible for the regulation of STOCs,whereas IP_(3)Rs might also be involved.
基金
Supported by the National Natural Science Foundation of China (Grant No. 30370527)
