三磷酸肌醇对猪冠状动脉平滑肌细胞大电导钙激活钾通道的作用

应用膜片钳单通道电流记录技术,研究三磷酸肌醇(trisphosphateinositol,IP3)对猪冠状动脉平滑肌细胞大电导钙激活钾通道(large-conductanceCa2+-activatedpotassiumchannels,BKchannels)的作用。结果显示:在内面向外式(inside-out)膜片下,IP3(10~50μmol/L)可以浓度依赖性地增加通道的开放概率,而对电流幅值无明显影响,开放概率的增加是通过明显缩短平均关闭时间实现的(n=11,P<0.01);洗去药物后通道活性可以恢复到对照水平;IP3对通道的激活作用不随时间而衰减;IP3的降解产物对通道没有明显的激活作用。结果表明:在inside-out膜片下,IP3能够激活猪冠状动脉平滑肌细胞BK通道。

Effect of IP3 on BK channels of porcine coronary artery smooth muscle cells

D-myo-inositol 1,4,5-trisphosphate (IP(3)) plays an important role in signal transduction. It releases Ca(2+) from intracellular sites, which activates the Ca(2+)-dependent channels such as large-conductance Ca(2+)-activated potassium channels (BK channels). The present study was therefore designed to determine if the activity of BK channels in porcine coronary artery smooth muscle cells was increased by IP(3). Using the inside-out patch-clamp technique, the activity of single BK channels was recorded in porcine coronary artery smooth muscle cells. In excised inside-out membrane patches, IP(3) (10-50 micromol/L) enhanced the open probability (Po) of BK channels in a dose-dependent manner in the intracellular side of inside-out patches and its effect was almost completely abolished by washout. The open-state probability of the BK channels increased from a control level of 0.0402+/-0.0152 to 0.1365+/-0.0212 (20 micromol/L IP(3)) and 0.1865+/-0.0175 (30 micromol/L IP(3)). IP(3) decreased the mean close time markedly, but had no effect on the amplitude of BK channels. The activation of IP(3) on BK channels did not decline. The metabolite of IP(3) had no obvious effect on BK channels. This study provides evidence that IP(3) activates BK channels in porcine coronary artery smooth muscle cells in a dose-dependence manner.