电脱耦联延迟参与κ-阿片受体兴奋引起的心肌保护作用

DELAYED ELECTRICAL UNCOUPLING IS INVOLVED IN κ-PIOIDRECEPTOR ACTIVATION-INDUCED CARDIOPROTECTIVE EFFECT IN THE ISOLATED RAT HEART

目的:研究κ-阿片受体兴奋诱导的心肌保护作用是否与其对心肌缺血期间电耦联的影响有关,并探讨这种作用的可能机理。方法:采用雄性SD大鼠心脏Langendorff离体灌流模型。①全心停灌30min,复灌2h,观察不同浓度κ-阿片受体特异激动剂U50,488H(10-7、10-6、3×10-6、和10-5mol/L)及其特异阻断剂nor-BNI(5×10-6mol/L)和线粒体ATP敏感性钾离子通道特异阻断剂5-HD(10-4mol/L)对缺血/复灌心肌的作用。测量指标:以分光光度计在490nm波长下测定氯化三苯基四氯唑(TTC)与活细胞反应的产物formazan含量的方法测定心肌细胞活性、测定冠脉流出液中乳酸脱氢酶(LDH)的含量以及心室内压;②全心停灌70min,应用四电极法观察不同浓度U50,488H、nor-BNI和5-HD对缺血期间心肌整体阻抗和电脱耦联参数(电脱耦联时间、平台时间、电脱耦联最大速率和阻抗倍数)的影响。结果:①U50,488H可诱导心肌保护作用,并呈浓度依从性,与对照组比较,表现为for-mazan含量增加,LDH释放减少,心室功能恢复增强;②经较高浓度U50,488H(10-6、3×10-6、和10-5mol/L)预处理后,电脱耦联时间和平台时间均延迟,电脱耦联最大速率降低;③U50,488H在10-7-10-5mol/L范围内对电脱耦联时间的延迟与其对formazan含量增加和LDH释放减少的作用呈线形相关;④U50,488H对formazan含量增加、LDH释放减少和电脱耦联时间和平台时间延迟的作用均可被nor-BNI或5-HD所阻断。结论:κ-阿片受体兴奋对电脱耦联的延迟作用与其诱导的心肌保护作用有关,这种作用受到线粒体ATP敏感性钾离子通道的调节。

Aim： To determine whether activation of κ-opioid receptor with U50,488H, a selective κ-opioid receptor agonist, produces any changes in electrical uncoupling during prolonged ischemia and whether these changes in electrical uncoupling is associated with the cardioprotection induced by κ-opioid receptor activation, and to explore the possible mechanism. Methods： （DTo observe the effect of U50,488H（10^-7, 10^-6, 3 × 10^-6 and 10^-5mol/L）, a selective κ-opioid receptor agonist, or with a selective κ-opioid receptor antagonist nor-BNI（5×10^-6mool/L） ,or with a rnitochondrial KATP channel inhibitor 5-HD on myocardium during ischemia/reperfusion in isolated perfused rat heart. Parameters of measurements include hemodynamie data, formazan content, heart rate, coronary flow, and lactate dehydrogenase（LDH）. ①To examine the effect of U50,488H of different concentration on electrical coupling parameters （including onset of uncoupling, plateau time, slope, and fold increase in rt） during 70 min myocardial ischemia in isolated perfused rat heart. Results： OPretreatment with U50,488H concentration dependently increased formazan content and reduced LDH release induced by 30 min of ischemia and 120 min of reperfusion. ②The onset of electrical uncoupling and plateau time during prolonged ischemia was delayed by κ-opioid receptor activation with U50,488H.③Linear regression analysis shown that the increase in formazan content and decrease in LDH release produced by κ-opioid receptor activation was associated with delayed electrical uncoupling during prolonged ischemia. ④The effects of U50,488H on formazan content, LDH release and on electrical coupling were abolished by nor BNI, or 5-HD. Conclusion ： This results demonstrate that the onset of electrical uncoupling during prolonged ischemia is delayed by κ-opioid receptor activation with a selective κ-opioid receptor agonist U50,488H, and that delayed electrical uncoupling is associated with the cardioprotection induced by κ-opioid receptor activation with U50,488H. These effects of κ-opioid receptor activation with U50,488H are mediated by mitochondrial KATP channels.