模拟失重可能降低大鼠心肌肌浆网功能

Function of Cardiac Sarcoplasmic Reticulum in Might be Depressed Rats During Simulated Weightlessness

采用离体乳头肌灌流、改变刺激频率和快速冷却等干预实验，探讨模拟失重４周大鼠心肌收缩性能降低的可能机理。结果表明：模拟失重大鼠乳头肌：（１）等长收缩达到张力峰值的时间明显延长；（２）细胞外Ｃａ＋浓度为８．０ｍｍｏｌ／Ｌ时，增加刺激频率，张力随之降低；（３）电刺激张力与停止电刺激ｌｓ的冷挛缩张力明显降低。这些均提示，模拟失重４周可能使心肌肌浆网Ｃａ＋＋摄取与释放速率降低。

The purpose of this study was to assess the function of cardiac sarcoplasmic reticuium in rats during simulated weightlessness. After 4 weeks of tail-suspension ,the isolated left ventricular papillary muscle showeda significant decrease in isometric contrac-tion tension(2.30±0.15 vs.3. 25± 0.22g/mm2P<0.01), and a prolongation in time to peak tension (141.3±2.9vs. 128.O±3.6 ms P<0.05). When extracellular Ca++concentration of the papillary preparation was controlled at 8. 0mmol/L, tension was decreased with increase of stimulation frequency in tail-suspended rats. Further-more,the ESC/RCC60 and RCC1/RCC60 were reduced in rapid cooling contracture test in tail-suspended rats. These results suggest that simulated weightlessness for 4 weeks may depress the rate of Ca++ release and uptake in cardiac sarcoplasmic reticulum.