模拟失重对大鼠心肌组织缝隙连接蛋白表达谱的影响

目的 研究模拟失重对大鼠心肌组织缝隙连接蛋白(CX)亚型表达谱的影响,为探讨模拟失重条件下心律失常部分发生机制提供新的实验依据.方法 将20只成年雄性Wistar大鼠随机平均分为正常对照组(Con)及尾部悬吊模拟失重组(SUS),应用电子透射电镜检测大鼠心肌组织超微结构,RT-PCR、Western bloting检测连接蛋白CX37、CX40、CX43、CX45 mRNA及CX40、CX43、CX45蛋白表达水平.结果 与Con组相比,模拟失重可致部分心肌细胞肌纤维变性,线粒体变性、数量减少,胶原增多,局部间隙连接增宽、结构消失.RT-PCR结果显示,SUS组心肌组织CX各亚型mRNA表达水平普遍显著下降,Western bloting结果显示,模拟失重条件下,CX43和CX45蛋白表达水平亦显著下降.结论模拟失重2 wk,大鼠心肌组织超微结构发生明显改变,缝隙连接出现非均质性结构变化,心肌组织缝隙连接蛋白表达谱普遍下调.结果提示,失重可以导致心肌缝隙连接蛋白重构,其可能影响心肌细胞间电兴奋传导的速度及方向,从而使传导阻滞和微折返易于出现,诱发心律失常.

Effects of Simulated Microgravity on the Gap Junction Protein Expression Spectrum in Rat Myocardium

Objective To investigate the effect of simulated microgravity on subtype expression spectra of connexins in rat myocardium,so as to provide new experimental bases for exploring the partial mechanism of cardiac arrhythmia under simulated microgravity.Methods Twenty male Wistar rats were equally and randomly assigned to either tail-suspension group(SUS)or control group(Con).Electromicroscope was used to observe the rat myocardium ultrastructure.RT-PCR was used to detect the mRNA of CX37,CX40,CX43 and CX45 in rat myocardium of the two groups,and Western blotting was used to detect the protein expression levels of CX40,CX43 and CX45.Results Contrast with Con,after tail suspenssion,there were some fiber degeneration,chondrosome degeneration,chondrosome reduce and collagen increase in partial myocardium.The gap between cardiac cells widened and the normal gap structure disappeared in some junctions.The mRNA expression levels of all four subtype connexins decreased significantly after tail suspension.The protein expression levels of CX43 and CX45 reduced too.But CX40 could not be detected by Western blotting method.Conclusion The results show that the heterogenous change of gap junction ultrastructure of rat myocardium can be induced and the level of connexin expression can be reduced significantly after 2 wk tail suspension.These changes may affect the electric transfer velocity and direction of myocardium,and then the electric conduction block and micro-reentry may occur.These might be the partial mechanism of cardiac arrhythmia under simulated microgravity.