吗啡后处理对大鼠心肌缺血再灌注损伤的影响及P13K／Akt信号通路在其中的作用

The role of PDK/Akt signaling pathway in the protective effect of morphine postconditioning on myocardium against ischemia-reperfusion injury in rats

目的评价吗啡后处理对大鼠心肌缺血再灌注损伤的影响及磷脂酰肌醇-3激酶／蛋白质丝氨酸苏氨酸激酶（P13K／Akt）信号通路在其中的作用。方法清洁级雄性SD大鼠70只，体重280～330g，年龄16～17周，随机分为5组（n=14）：假手术组（S组）、缺血再灌注组（IR组）、吗啡后处理组（M组）、渥曼青霉素＋吗啡后处理组（W＋M组）和渥曼青霉素组（W组）。采用结扎左冠状动脉前降支45min、再灌注t20min的方法制备心肌缺血再灌注模型。S组仅穿线，不结扎；M组于再灌注前3min和再灌注后2min时经左颈内静脉注射吗啡1．25mg／kg；W＋M组于结扎左冠状动脉前降支前20min时经左颈内静脉注射P13K特异性阻断剂渥曼青霉素15μg／kg，并行吗啡后处理；W组于结扎左冠状动脉前降支前20min时经左颈内静脉注射渥曼青霉素15μg／kg。于左冠状动脉前降支阻断前即刻、阻断20min和再灌注120min（T1-3）时记录心率（HR）、平均动脉压（MAP）和心率-收缩压乘积（RPP）；于再灌注120min时各组随机取9只大鼠，计算心肌缺血和梗塞范围；其余5只大鼠采用Western blot法测定心肌组织总Akt和磷酸化Akt的表达水平。结果五组HR、MAP、RPP、心肌缺血范围和总Akt表达水平比较差异无统计学意义（P〉0．05）；与T1时比较，IR组、M组、S＋M组和W组再灌注时MAP和RPP均降低（P〈0．05）；与S组比较，IR组和M组磷酸化Akt表达上调（P〈0．05），W＋M组和W组差异无统计学意义（P〉0．05）；与IR组比较，M组心肌梗塞范围缩小，心肌组织磷酸化Akt表达上调（P〈0．01），W＋M组和W组心肌梗塞范围差异无统计学意义（P〉0．05）。结论吗啡后处理可减轻大鼠心肌缺血再灌注损伤，可能与进一步激活P13K／Akt信号通路有关。

Objective To investigate the effect of morphine postconditioning on myocardial ischemiareperfusion （I/R） injury and the role of PI3K/Akt signaling pathway in the effect. Methods Seventy male SD rats weighing280-330 g aged 16-17 weeks were randomly divided into 5 groups （n = 14 each）： group Ⅰ sham operation （S）; group Ⅱ I/R; group Ⅲ morphine postconditioning （M）; group Ⅳ morphine postconditioning ＋ wortmannin （W ＋ M） ; groupV wortmannin （W） . Myocardial I/R injury was produced by occlusion of anterior descending branch of left coronary artery for 45 min followed by 120 min reperfusion. In group M and W ＋ M （group Ⅲ, Ⅳ ） morphine 1.25 mg/kg was given iv at 3 min before and 2 min after reperfusion. In group W ＋ M and W （group Ⅳ , Ⅴ ） wortmannin （a specific PI3K inhibitor） 15μg/kg was given iv at 20 min before ischemia. The animals were sacrificed at the end of 120 rain reperfusion for assessment of ischemic and infarct area and detel Tnination of total and phosphorylated Akt expression in myocardium by Western blot. Results There were no significant differences in the size of ischemic area and total Akt expression among the 5 groups. The infarct area was significantly smaller in group M than in group I/R. The were no significant differences in the size of infarct area between group I/R, W ＋ M and W （group Ⅱ , Ⅳ, Ⅴ ）. The phosphorylated Akt expression was significantly up- regulated in group I/R and M as compared with group S, and was significantly higher in group M than in group I/R.Conclusion The PI3K/Akt signaling pathway activation is involved in the protective effect of morphine postconditioning on myocardium against I/R injury.