Cai Fang, Zeng Xiao-Rong, Yang Yan, Liu Zhi-Fei, Li Miao-Ling, Zhou Wen, Pei Jie
Institute of Myocardial Electrophysiology, Luzhou Medical College, Luzhou 646000, China.
Sheng Li Xue Bao. 2005 Jun 25;57(3):303-9.
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.
D-肌醇1,4,5-三磷酸（IP(3)）在信号转导中起重要作用。它从细胞内位点释放Ca(2+)，从而激活Ca(2+)依赖性通道，如大电导Ca(2+)激活钾通道（BK通道）。因此，本研究旨在确定IP(3)是否能增加猪冠状动脉平滑肌细胞中BK通道的活性。采用内面向外膜片钳技术，记录猪冠状动脉平滑肌细胞中单个BK通道的活性。在切除的内面向外膜片中，IP(3)（10 - 50 μmol/L）在内面向外膜片的细胞内侧以剂量依赖性方式增加BK通道的开放概率（Po），且冲洗后其作用几乎完全消失。BK通道的开放态概率从对照水平的0.0402±0.0152增加到0.1365±0.0212（20 μmol/L IP(3)）和0.1865±0.0175（30 μmol/L IP(3)）。IP(3)显著缩短了平均关闭时间，但对BK通道的幅度没有影响。IP(3)对BK通道的激活作用没有下降。IP(3)的代谢产物对BK通道没有明显影响。本研究提供了证据表明IP(3)以剂量依赖性方式激活猪冠状动脉平滑肌细胞中的BK通道。
