Ionic current study by patch clamp and its relation to the coronary artery spasm

应用膜片钳技术记录血管平滑肌细胞的宏观电流。与平滑肌细胞从豚鼠膀胱，去极化电压阶跃引起和初始内向电流，然后由外向电流，而与平滑肌细胞的肠系膜动脉，去极化脉冲引起专门和外向电流。在用110 mM Ba溶液替换移液管中的溶液时，观察到来自血管平滑肌细胞的内向电流。这一电流被维拉帕米阻断。这些结果表明，血管平滑肌细胞在正常条件下不产生类钙离子，因为外向电流远大于内向电流。在冠状动脉平滑肌细胞的膜片钳单通道记录中，观察到许多不同电导的钙依赖性K通道，它们抑制Ca ~（2+）进入细胞时Ca ~（2+）峰的形成。我们还发现了一个新的钾通道，控制平滑肌细胞的收缩。该通道依赖于外部Ca和/或Mg，被4-氨基吡啶阻断，并被尼可地尔和SITS打开。结果表明，钾通道电流是控制动脉平滑肌细胞收缩的重要因素。

The loose patch clamp method was applied to the vascular smooth muscle cells to record their macroscopic current. With smooth muscle cells from the urinary bladder of guinea pigs, depolarizing voltage steps elicited and initial inward current followed by an outward current, while with smooth muscle cells of the mesenteric artery, depolarizing pulses elicited exclusively and outward current. On replacing the solution in the pipette by 110 mM Ba solution, an inward current was observed from the vascular smooth muscle cells. This current was blocked by verapamil. These results indicate that vascular smooth muscle cells do not produce a Ca-soike in normal conditions because the outward current is much larger than the inward current. But these cells do have a slow inward current and can presumably generate a Ca-spike in certain abnormal conditions, in which the outward current is decreased.In single channel recording of coronary artery smooth muscle cells by patch clamp, many Ca-dependent K channels with various conductance were observed, which inhibit developement of Ca-spike when Ca ion enters the cell. We also found a novel K channel which control contraction of the smooth muscle cells. This channel was dependent external Ca and/or Mg, blocked by 4-aminopyridine and opened by nicorandil and SITS. With decrease in this K current, smooth muscle cells contracts.These results suggest that K channel current is an important factor to control contraction of the smooth muscle cell of the artery.