缺血及二氮嗪预适应对大鼠缺血再灌注心肌的保护作用

Protective effect of ischemia and diazoxide preconditioning on postischemic reperfused myocardium and possible mechanism thereof

目的探讨缺血及二氮嗪预适应对大鼠缺血再灌注心肌的保护作用及机制。方法Wistar大鼠30只，建立离体心脏灌注模型，分成3组，每组10只：（1）缺血再灌注组（I／R组）：心脏平衡灌流30min后，缺血30min，再灌注1h。（2）缺血预适应组（IPC组）：心脏平衡灌流10min，经2次缺血再灌注。（3）二氮嗪预适应组（DPC组）：心脏平衡灌流10min，给予2次含二氮嗪（100μmol／1）的K—H液灌注5min再复灌不含二氮嗪的K—H液，缺血30min，再灌注1h。各组取心尖肌做冰冻切片行过氧化物酶体增生激活受体γ协同刺激因子1α（PGC-1α）免疫组织化学染色，电镜标本对心肌线粒体行Flameng评分。结果IPC组、DPC组PGC-1α表达明显增高，与I／R组比较差异有统计学意义，但IPC及DPC两组间差异无统计学意义（P〉0．05）。Flameng评分：IPC组（0．44±0．13）、DPC组（0．47±0．10）、I／R组（1．78±0．14）；IPC及DPC两组与I／R组比较差异有统计学意义（均P〈0．01）。结论缺血及二氮嗪预适应对心肌线粒体有保护作用，这一作用可能与PGC-1α激活及高表达有关。

Objective To study the protective mechanism of ischemic preconditioning （IPC） and diazoxide preconditioning （DPC） against myocardium ischemia-reperfusion （I/R） injury. Methods The hearts were taken out from 30 male Wistar rats and were divided randomly into 3equal groups： I/R group undergoing 30-min equilibration perfusion and 30-min ischemia and then 60-min reperfusion, [PC group undergoing 10-min equilibration perfusion and then two cycles of 5 min ischemia interspersed with 5 min reperfusion prior to 30 min ischemia and a 60-min reperfusion, and DPC group undergoing 10-min equilibration perfusion and 2 cycles of 5 min of 100 μM diazoxide perfusion followed by 5-min drug-free period before the 30 min ischemia and 60-min reperfusion. Frozen sections of myocardium at the cardiac apex were made and immunohistochemical staining was used to detect the expression of peroxisome proliferator-activated receptor-γ coactivator 1α （PGC-1α）. Ultrathin sections 70 nm thick were made and transmission electron microscopy was used to detect the structure of the mitochondria with the Flameng scoring system. Results The PGC-1α expression of the IPC and DPC groups were significantly higher than that of the I/R group （P 〈 0.01 and P 〈 0.05）, however, there was no significant difference in PGC-1α is expression between the IPC and DPC groups （ P 〉 0.05 ）. The Flameng scores of the IPC and DPC groups were 0.44 ± 0. 13 and 0.47 ± 0. 10 respectively, both significantly higher than that of the I/R group （ 1.78 ± 0.14, both P 〈 0.01 ） , however, there was no significant difference between IPC and DPC groups （P 〉 0.05）. Conclusion IPC and DPC can protect myocyte mitochondria from the injury of ischemia/ reperfusion. The cardioprotective effects of IPC and DPC may be concerned with the activation and high expression of PGC-1α.