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

点击翻译按钮获取中文摘要

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.