缺血预适应对再灌注性心肌超微结构损伤和细胞凋亡的保护作用

Ischemic preconditioning in protection of myocardial ultrastructure and inhibition of apoptosis in ischemia and reperfusion injury in felines during cardiopulmonary bypass

目的 :研究体外循环 (CPB)中缺血预适应 (IPC)对缺血再灌注心肌超微结构损伤的保护作用及其对细胞凋亡的影响。方法 :建立猫 CPB模型并随机分成 3组。对照组 (n=30 )仅作单纯并行 CPB转流 ;缺血再灌注组 (IR组 ,n=30 )于 CPB开始 4 5 m in后阻断升主动脉 (ACC) 6 0 m in,开放主动脉恢复再灌注 90 m in;IPC组 (n=30 )于 ACC前进行 3轮 IPC(ACC5 min后开放 1 0 m in) ,余同 IR组。应用透射电镜观察心肌超微结构的变化 ,计算心肌细胞凋亡率 ,并结合细胞化学方法观察心肌超微结构中过氧化氢 (H2 O2 )电子致密物沉积的产生及细胞内 Ca2 +分布情况。 结果 :IR组 ACC6 0 min心肌细胞超微结构损伤较重 ,尤其是线粒体及血管内皮细胞肿胀明显 ,再灌注期间进一步加重 ,至再灌注结束时 ,未见明显改善 ;IPC组心肌细胞超微结构损伤较 IR组明显减轻。至再灌注 90 min时 ,IR组和 IPC组均可发现一定数量的凋亡心肌细胞 ,心肌细胞凋亡率分别为(8.82 7± 0 .973) %和 (2 .2 4 3± 0 .2 4 6 ) % ,两者之间具有显著性差异 (P<0 .0 5 ) ;IR组在心脏恢复再灌注后 ,其心肌中血管内皮细胞管腔面可见较多的 H2 O2 电子致密物沉积 ,而且细胞内 Ca2 + 分布也明显增加 ;IPC组 H2 O2 电子致密物沉积和细胞内Ca2 +

Objective:To evaluate the protective effect of ischemic preconditioning (IPC) on the myocardial ultrastructure in ischemia and reperfusion (IR) injury and on inhibition of apoptosis during the cardiopulmonary bypass (CPB).Methods:Ninety felines were randomized into 3 groups:control group( n =30),in which CPB was conducted without aortic cross clamping (ACC); IR group( n =30),with 60 min ACC followed by 90 min reperfusion,and cardioplegia was used during period of ACC; IPC group( n =30),with protocol similar to that of IR group except for three round 15 min IPC applied before ACC.The ultrastructural change of the myocardium was observed under electron microscope and the apoptosis ratio of cardiomyocyte was also determined.H 2O 2 and intracellular Ca 2+ electron deposits distribution were observed by the electron microscope technique combined with the cytochemical technique.Results:During ACC period,the most significant ultrastructural changes were mitochondrial swelling and damage of capillary endothelium,which were more severe in IR group.The amounts of H 2O 2 deposits and intracellular Ca 2+ were significantly increased during reperfusion.Cardiomyocyte apoptosis was only documented during the period of reperfusion and IPC markedly attenuated the apoptosis ratio of cardiomyocyte caused by reperfusion from (8.827±0.973) % in IR group to (2.243±0.246) % in IPC group at 90 min of reperfusion ( P <0.05).At the same time point of CPB,the amount of both H 2O 2 and calcium deposits were evidently lower in IPC group than in IR group.Conclusion:IPC can protect myocardial cells from IR injury and apoptosis by reducing the production of oxygen free radicals and calcium overload during the reperfusion period of CPB.