U50,488H对缺血期间心肌电耦联的影响及其机制研究

目的:研究κ-阿片受体特异性激动剂U50,488H对心肌缺血后电耦联特性的影响,并探讨其作用的可能机制。方法:采用雄性SD大鼠心脏Langendorff离体灌流模型和四电极法,观察U50,488H对全心停灌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。采用免疫组化染色法检测U50,488H对左心室心肌细胞缝隙连接结构蛋白Cx43的影响,并同时观察U50,488H特异阻断剂nor-BNI(5×10-6mol/L)和PKC抑制剂chelerythrine(3×10-6mol/L)预处理对U50,488H作用的影响。结果:U50,488H可浓度依赖地延迟电脱耦联时间和平台时间,降低电脱耦联最大速率;nor-BNI或chelerythrine预处理均可明显减弱U50,488H对心肌缺血后电耦联特性的作用;与空白对照组比较,单纯缺血组心肌闰盘处Cx43蛋白显著减少,U50,488H处理可明显增加缺血心肌闰盘处Cx43蛋白含量;nor-BNI和chelerythrine预处理均可明显减弱U50,488H对心肌Cx43蛋白表达的作用。结论:κ-阿片受体激动剂U50,488H明显延迟缺血诱导的心肌电脱耦联,其作用涉及κ-阿片受体-PKC途径,其作用靶点可能为心肌细胞缝隙连接蛋白Cx43。

The study of effects and mechanism of U50, 488H on electrical coupling during ischemia in the perfused isolated rat heart

Objective： To detemline the effect of activation of κ-opioid receptor with U50, 488H, a selective κ-opioid receptor agonist, on the changes in electrical coupling during prolonged ischemia and to explore the possible mechanism. Methods： The isolated rat heart was perfused in a Langendorff apparatus. The effect of U50, 488H on electrical coupling parameters including onset of uncoupling, plateau time, slope and fold increase in rt was observed in isolated perfused rat heart subjected to global no-flow isehemia. The effect of U50, 488H on connexin 43（Cx43） expression of ventricular muscle during isehemia was determined by immunohistoehemistry. Results： In the prolonged ischemia model, U50, 488H concentration dependently delayed the onset of uncoupling, increased time to plateau, and decreased the maximal rate of uncoupling dtLring isehemia. The effect of U50, 488H on electrical uncoupling parameters during ischemia was abolished by a selective κ-opioid receptor antagonist nor-BNI or a PKC inhibitor ehelerythrine. The amount of Cx43 immunoreactive signal in ven/ficular muscle was greatly reduced after ischemia. U50, 488H markedly increased Cx43 expression during ischemia and its effect was also attenuated by nor-BNI or chelerythrine. Conclusion： These results demonstrated that U50, 488H delayed the onset of uncoupling and plateau time, decreased the maximal rate of uncoupling and increased Cx43 expression of ventricular muscle during ischemia, and these effects of U50, 488H were mediated by κ- opioid receptor, in which activation of PKC was involved. The effect of U50, 488H on electrical coupling during ischemia was probably correlated with preservation of Cx43 in cardiac muscle.