Effects of caffeine and ryanodine on KCa in porcine coronary artery smooth muscle cells / 中国病理生理杂志

ABSTRACT

AIM:To study the effect of caffeine on the large conductance calcium activated potassium (KCa) channels by patch-clamp technique on smooth muscle cells enzymatically isolated from the porcine coronary artery (PCASMC),and to investigate the effect of ryanodine on KCa being activated by caffeine.METHODS:Using the single channel patch-clamp technique,single PCASMC was isolated by collagenase,the activity of single KCa channel was recorded in porcine coronary artery smooth muscle cells.RESULTS:Caffeine (0.1-10 mmol/L) enhanced the open probability (Po) of KCa channels in a dose-dependent manner in the intracellular side of inside-out patches and its effect was almost completely abolished by washout. Caffeine decreased the mean close time markedly,but had no effect on the amplitude of KCa channels. However,ryanodine (10-40 ?mol/L) decreased Po of KCa channels activated by caffeine in a dose-dependent manner in cell-attached patches. The mean open time also decreased.CONCLUSION:Caffeine directly activates KCa channels of porcine coronary artery smooth muscle cells in inside-out patches,the activity of single KCa channel is inhibited by ryanodine indirectly in cell-attached patches.