内源性K-阿片肽介导的缺血后处理心肌保护作用

目的：研究内源性K-阿片受体（K-OR）的激动剂强啡肽在触发缺血后处理（postconditioning，Postcon）中的抗凋亡作用及潜在机制。方法：除了假手术组，SD大鼠（每组6只）制作缺血再灌注模型，进行了左冠状动脉前降支闭合30分钟后，再灌注2小时伴有或不伴有缺血后处理。在再灌注前5分钟静脉注射选择性K-受体拮抗剂nor-binaltorphimine（nor-BNI）。氯化三苯四染色测定心肌梗死面积。用分光光度计测定血浆中肌酸激酶（CK）、乳酸脱氢酶（LDH）水平和心肌细胞凋亡蛋白酶-3（caspase-3）活性。TUNEL法检测心肌细胞凋亡。ELISA法检测血清和心肌中强啡肽含量。结果：缺血／再灌注（I依组）组的梗死面积，caspase-3活性，细胞凋亡指数，CK和LDH活性等明显高于假手术组（P〈0．01）。与I／R组相比，Postcon明显减少梗死面积，caspase-3活性，细胞凋亡指数，CK及LDH活性（P〈0．01）。Postcon可使强啡肽含量显著增加（P〈0．01）。除强啡肽含量外，上述所有的作用均被nor-BNI所阻断。结论：心脏保护和后处理的抗凋亡作用是通过激活K-OR，至少部分通过增加强啡肽的水平来介导的。

Endogenous Kopioid Peptide Mediated Ischemic Postconditioning for Cardioprotectiong

Objective： To investigate the mechanism of dynorphin, an endogenous kappa opioid receptor （K -OR） agonist in postconditioning （Postcon）. Methods： Sprague Dawley （SD） rats （n=6） underwent a 30-min left anterior descending occlusion followed by 2h of reperfusion with or Without a Postcon stimulus. The selective K -OR antagonist nor-binaltorphimine （Nor-BNI） was administered Lv. 5 min before reperfusion. Infarct size was determined by triphenyltetrazolium chloride staining. Blood plasma of creatine kinase （CK） and lactate dehydrogenase （LDH） and myocardial caspase-3 activity were analyzed by spectrophotometrically. Myocardial apoptosis was analyzed by detection of TUNEL. Immunoreactive dynorphin in blood serum and myocardium was measured by an antigen-competitive ELISA. Results： Infarction size, caspase-3 activity, apoptotic index, CK and LDH were significantly higher in ischemic/reperfusion （I/R） group than that in vehicle group （P〈0.01）. Postcon reduced infarction size, caspase-3 activity, apoptotic index, CK and LDH （P〈0.01 vs. I/R）. Dynorphin content significantly increased after Postcon （P〈0.01）. All indexes described above were abolished by Nor-BNI, with the exception of dynorphin content. Conclusion： Cardiac protection and anti-apoptotic effect of Postcon is mediated by activation of K -OR. Effect of Postcon is mediated, at least partially, by enhanced dynorphin expression.