Xie Man-Jiang, Zhang Li-Fan, Ma Jin, Cheng Hong-Wei
Department of Aerospace Physiology, Fourth Military Medical University, Xioan 710032, China;E-mail:
Sheng Li Xue Bao. 2005 Aug 25;57(4):439-45.
The aim of the present study was to investigate the changes in single-channel currents of large conductance calcium-activated potassium channels (BK(Ca) channels) in cerebral vascular smooth muscle cells (VSMCs) of rats after 1-week simulated microgravity. Sprague-Dawley rats were subjected to tail-suspension (SUS) to simulate cardiovascular deconditioning due to microgravity. Cytosolic calcium (Ca(2+)) was examined by laser-scanning confocal microscopy with calcium-sensitive-dye Fluo-3/AM as fluorescent probe. Single-channel currents of BK(Ca) channels were measured with cell-attached membrane patches bathed in symmetrical high potassium solution. The Ca(2+)i level was significantly higher in cerebrovascular myocytes of SUS than that of control (CON) rats. The probability of open (Po) and the mean open time (To) of BK(Ca) channels in cerebral VSMCs significantly increased in SUS as compared with CON. However, there were no significant differences in the unitary conductance and mean close time (Tc) between the two groups. The results obtained suggest that both the elevated Ca(2+) and enhanced single-channel activities of BK(Ca) channels in cerebral VSMCs might be among the electrophysiological mechanisms that mediate the increased vasoreactivity and hypertrophic change in cerebral arteries during adaptation to simulated microgravity in rats.
本研究的目的是探讨大鼠脑血管平滑肌细胞（VSMCs）在1周模拟微重力后大电导钙激活钾通道（BK(Ca)通道）单通道电流的变化。将Sprague-Dawley大鼠进行尾吊（SUS）以模拟由于微重力导致的心血管失适应。以钙敏染料Fluo-3/AM作为荧光探针，通过激光扫描共聚焦显微镜检测胞质钙（Ca(2+)）。在对称的高钾溶液中，用细胞贴附膜片钳记录BK(Ca)通道的单通道电流。SUS组大鼠脑血管肌细胞中的Ca(2+)水平显著高于对照组（CON）大鼠。与CON组相比，SUS组大鼠脑血管VSMCs中BK(Ca)通道的开放概率（Po）和平均开放时间（To）显著增加。然而，两组之间的单位电导和平均关闭时间（Tc）没有显著差异。所得结果表明，大鼠在适应模拟微重力过程中，脑血管VSMCs中Ca(2+)升高和BK(Ca)通道单通道活性增强可能是介导脑动脉血管反应性增加和肥厚性变化的电生理机制之一。
