尼可地尔预先给药对兔心肌缺血再灌注时心肌线粒体的影响

目的 评价尼可地尔预先给药对兔心肌缺血再灌注时心肌线粒体的影响.方法 雄性新西兰白兔32只,随机分为4组(n=8),假手术组(S组)仅在左冠状动脉旋支中点穿线;I/R组、尼可地尔组(N组)和尼可地尔+5-羟葵酸组(N+5-HD组)均进行心肌缺血30 min.N组和N+5-HD组缺血前10 min静脉注射尼可地尔100μg/kg负荷量,随后以10μg·kg-1·min-1的速率静脉输注至缺血前即刻;N+5-HD组在缺血前20 min静脉注射线粒体ATP敏感性K+通道阻断剂5-羟葵酸5 mg/kg.再灌注120 min时,取心肌组织,测定线粒体膜电位、心肌Bcl-2、Bax和细胞色素c(Cyt c)表达水平,计算Bcl-2和Bax表达的比值(Bcl-2/Bax).电镜下观察线粒体超微结构.结果 与S组比较,其余3组线粒体膜电位、Bcl-2/Bax降低,Cyt c表达上调(P＜0.05);与I/R组比较,N组线粒体膜电位、Bcl-2/Bax升高,Cyt c表达下调(P＜0.05).N组线粒体损伤程度轻于I/R组.5-羟葵酸可逆转尼可地尔导致的上述改变.结论 尼可地尔预先给药可保护线粒体膜电位,减少Cyt c易位至胞浆,从而抑制兔心肌缺血再灌注时细胞凋亡,其机制与开放线粒体ATP敏感性K+通道有关.

Effect of nicorandil pretreatment on myocardial mitochondria in a rabbit model of myocardial ischemia-reperfusion

Objective To investigate the effect of nicorandil pretreatment on myocardial mitochondria in a rabbit model of myocardial ischemia-reperfusion (I/R). Methods Tirty-two healthy male New Zealand white rabbits weighing 2.0-2.5 kg aged 4 months were randomly allocated into 4 groups ( n = 8 each): Ⅰ group sham operation (group S); Ⅱ group I/R; Ⅲ group nicorandil pretreatment (group N) and Ⅳ group nicorandil + 5 hydroxydecanoic acid (group N + 5-HD). Myocardial I/R was induced by 30 min occlusion of left circumflex coronary artery followed by 120 min reperfusion. In group N and N + 5-HD a bolus of nicorandil 100 μg/kg was given iv at 10 min before myocardial ischemia followed by continuous infusion at 10 μg· kg-1 · min-1 until the beginning of myocardial ischemia. In group Ⅳ a bolus of 5-HD 5 mg/kg was injected iv at 20 min before myocardial ischemia.The animals were sacrificed at the end of 120 min reperfusion. The mitochondrial membrane potential was measured by flow cytometry using JC-1 fluorescence probe as indicator. Bcl-2, Bax and cytochrome c protein expression was determined by immuno-histochemistry. Myocardial ultrastructure was examined with transmission electron microscope. Results Red fluovescence intensity indicating normal live cells was significantly higher, the green fluorescence intensity indicating apoptotic cells was lower and red/green fluorescence intensity ratio was higher; the Bcl-2/Bax ratio was significantly higher and cytochrome c protein expression lower in group N than in group I/R.5-HD administration negated the protective effect of nicorandil pretreatment against myocardial I/R injury. Conclusion Nicorandil stabilizes mitochondrial membrane potential, decreases cytochrome c protein releasing, and suppresses mitochondrial apoptotic signal transduction by opening the mito-KATP channels.