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目的 :研究机械牵张对模拟缺血状态下体外豚鼠乳头肌动作电位 (AP)的影响。方法 :建立模拟缺血条件下体外豚鼠乳头肌机械牵张模型 ,2 4只豚鼠随机分为正常对照组、单纯缺血组和缺血加链霉素组 ,每组 8只。利用细胞内标准玻璃微电极技术 ,记录并观察一定牵张力 ( 2 0 0mg强度 )作用下体外豚鼠乳头肌细胞AP各参数 [AP 0相最大升速率 (Vmax)、AP幅值 (APA)、AP复极达 2 0 %的时程 (APD2 0 )、AP复极达 5 0 %的时程(APD50 )和AP复极达 90 %的时程 (APD90 ) ]的变化。结果 :正常对照组牵张前后AP各参数无明显变化 (均P >0 .0 5 ) ;与正常对照组相比 ,单纯缺血组和缺血加链霉素组在牵张前上述参数均显著降低 (均P <0 .0 1) ;单纯缺血组 ,牵张使AP的Vmax和APA显著下降 ,APD2 0 、APD50 和APD90 明显缩短 (均P <0 .0 1) ;在缺血加链霉素组 ,牵张前后AP的上述指标无显著变化 (均P >0 .0 5 )。结论 :机械牵张易导致缺血心肌电生理参数变化 ,即缺血心肌对牵张反应的敏感性增加 ;而且牵张激活性离子通道阻滞剂———链霉素可以有效抑制该效应
Objective: To study the effect of mechanical stretch on the action potential (AP) of guinea pig papillary muscle in vitro under simulated ischemia. Methods: Mechanical distraction model of guinea pig papillary muscle was established under simulated ischemia. 24 guinea pigs were randomly divided into normal control group, ischemia group and streptomycin group, with 8 rats in each group. Intracellular standard glass microelectrode technique was used to record and observe AP parameters (the maximal AP 0 phase velocity (Vmax), AP amplitude (APA), AP APD20, APD50 + APD90 and 90% APD90 of AP complex) were measured. Results: Compared with the normal control group, the parameters of AP before and after distraction in normal control group showed no significant change (all P> 0.05) (P <0.01). In pure ischemic group, the Vmax and APA of AP were significantly decreased and APD20, APD50 and APD90 were significantly shortened (all P <0.01) Streptomycin group, stretch before and after AP of the above indicators no significant change (P> 0.05). CONCLUSIONS: Mechanical stretch easily leads to changes of electrophysiological parameters of ischemic myocardium, ie, the sensitivity of ischemic myocardium to stretch-response increases; and stretch-activated ion channel blocker streptomycin can effectively inhibit this effect