模拟失重增强大鼠脑动脉血管平滑肌细胞大电导钙激活钾通道功能

Enhanced BK_(Ca) single-channel activities in cerebrovascular smooth muscle cells of simulated microgravity rats

本工作旨在探讨短期模拟失重大鼠脑动脉血管平滑肌细胞(vascularsmoothmusclecells,VSMCs)大电导钙激活钾通道(largeconductancecalcium-activatedpotassiumchannels,BKCachannels)功能的改变。以尾部悬吊大鼠模型模拟失重对脑血管的影响。应用激光扫描共聚焦显微镜测定VSMCs胞内游离钙浓度([Ca2+]i);采用细胞贴附模式,记录BKCa通道的单通道活动。结果表明,模拟失重1周后,大鼠脑动脉VSMCs的[Ca2+]i比对照组显著升高(P<0.05);BKCa通道的开放概率(Po)与平均开放时间(To)显著增加(P<0.05),而单通道电导与平均关闭时间(Tc)则无显著变化。总之,1周模拟失重可引起脑动脉VSMCs的BKCa通道功能显著增强,且与细胞[Ca2+]i的升高同步出现。结果提示,脑动脉VSMCs的离子通道机制可能参与介导模拟失重引起的脑血管适应性变化。

The aim of the present study was to investigate the changes in single-channel currents of large conductance calcium-activated potassium channels （BKca 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＋]i） was examined by laser-scanning confocal microscopy with calcium-sensitive-dye Fluo-3/AM as fluorescent probe.Single-channel currents of BKCa 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 BKca 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 2 elevated[Ca^2＋]i and enhanced single-channel activities of BKCa 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.