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Enhanced BKCa single-channel activities in cerebrovascular smooth muscle cells of simulated microgravity rats

Xie Manjiang, Zhang Lifan, Ma Jin, Cheng Hongwei

Department of Aerospace Physiology, Fourth Military Medical University. Xian 710032, China

Abstract

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 ([Ca2+]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 [Ca2+]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 elevated [Ca2+]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.

Key words: Microgravity;Postspaceflight cardiovascular deconditioning;Rat;Vascular smooth muscle cells;Cytosolic calcium;Large conductance calcium-activated potassium channel

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Citing This Article：

Xie Manjiang, Zhang Lifan, Ma Jin, Cheng Hongwei. Enhanced BKCa single-channel activities in cerebrovascular smooth muscle cells of simulated microgravity rats . Acta Physiol Sin 2005; 57 (4): (in Chinese with English abstract).