一氧化氮在吗啡后处理抑制大鼠缺血再灌注心肌细胞凋亡中的作用

目的 探讨一氧化氮在吗啡后处理抑制大鼠缺血再灌注损伤心肌细胞凋亡中的作用.方法 清洁级雄性SD大鼠60只,体重280～330 g,随机分为4组(n=15):假手术组(S组)只穿线不结扎;缺血再灌注组(I/R组)结扎左冠状动脉前降支45 min,再灌注120 min;吗啡后处理组(M组)再灌注前3 min至再灌注2 min经左颈内静脉注射吗啡1.25 mg/kg;L-NAME+吗啡后处理组(L+M组)左冠状动脉前降支结扎前20 min静脉注射L-NAME 10 mg/kg.分别于缺血前、缺血20 min及再灌注120 min时监测心率(HR)和平均动脉压(MAP),并计算HR与收缩压(SP)的乘积(RPP);于再灌注120 min时取心肌,采用TUNEL法检测心肌凋亡细胞,计算心肌细胞凋亡指数(AI),采用Western blot法检测总内皮型一氧化氮合酶(eNOS)和磷酸化eNOS蛋白的表达水平,计算磷酸化eNOS蛋白表达与总eNOS蛋白表达的比值(p-eNOS/eNOS),硝酸盐还原酶法测定心肌NO含量.结果 I/R组、M组及L+M组间各时点HR、MAP及RPP差异无统计学意义(P>0.05);与S组比较,其余各组AI升高,I/R组和L+M组心肌NO含量降低,M组升高(P<0.05);与I/R组比较,M组AI降低,M组心肌NO含量升高(P<0.05),L+M组差异无统计学意义(P>0.05),M组和L+M组p-eNOS/eNOS升高(P<0.05);与M组比较,L+M组AI升高,心肌NO含量降低(P<0.05),p-eNOS/eNOS差异无统计学意义(P>0.05).结论 吗啡后处理可通过激活eNOS促进NO产生,抑制大鼠缺血再灌注损伤诱发的心肌细胞凋亡.

Role of nitric oxide in the protective effect of morphine postconditioning against ischemia-reperfusion-induced myocardial apoptosis

Objective To investigate the role of nitric oxide (NO) in the protective effects of morphine postconditioning against ischemia-reperfusion (I/R)-induced myocardial apoptoais. Methods Sixty pathogen-free SD rats were randomly divided into 4 groups ( n = 15 each) : group Ⅰ sham operation (S) ; group Ⅱ I/R; group Ⅲ morphine postconditioning ( M ) and group Ⅳ M + L-NAME ( non-selective NOS inhibitor). The animals were anesthetized with intraperitoneal pentobarbital 60 mg/kg, tracheostomized and mechanically ventilated. ECG was monitored. Right carotid artery was cannulated for BP monitoring and left jugular vein was cannulated for drug and fluid administration. Myocardial ischemia was induced by 45 min occlusion of left anterior descending coronary artery (LAD) followed by 120 min reperfusion. In group S LAD was exposed but not occluded; in group M morphine 1.25 mg/kg was injected iv over 5 min from 3 min before reperfuaion to 2 min of repeffuaion and in group M + L-NAME L-NAME 10 mg/kg was injected iv at 20 min before myocardial ischemia. Hemodynamic changes were monitored. The animals were killed at the end of 120 min reperfusion and their hearts removed. Myocardial apoptosis was determined by TUNEL technique. The expression of Akt phosphorylation was assessed by Western blotting. The NO content in myocardium was measured by a chemiluminescence detector.Results A large number of TUNEL positive cells (18.4 ± 1.1 ) % were observed in group I/R. Morphine postconditioning exerted a significant anti-apoptotic effect. The number of TUNEL positive cells was reduced to (10.8 ± 1.2)%. The myocardial eNOS phosphorylation expression and NO content were significantly increased in group M as compared with group I/R. The anti-apoptofie effect and increased NO production were significantly reversed by L-NAME. However, pretreatment with L-NAME did not inhibit the phosphorylation of eNOS in group L + M. Conclusion In vivo, morphine postconditioning can significantly reduce I/R-induced myocardial apoptosis through phosphorylation of eNOS and increase in NO production.