G蛋白在亮啡肽诱导心肌细胞内钙释放中的作用

THE ROLE OF G PROTEIN IN LEU-ENKEPHALIN INDUCED Ca￣(2+) RELEASE FROM INTRACELLULAR POOL IN MYOCYTES

本实验采用分离的ＳＤ大鼠心室肌细胞，以Ｆｕｒａ－２ＡＭ荧光指示剂负载，检测心肌细胞内游离钙浓度（［Ｃａ２＋］ｉ）变化。探讨亮啡肽（ＬＥＫ）对［Ｃａ２＋］ｉ的作用及其机制。实验结果：ＬＥＫ（６０μｕｍｏｌ／Ｌ）能升高［Ｃａ２＋］ｉ，移去细胞外液钙此效应仍能出现，用ｃａｆｆｅｉｎｅ（５ｍｍｏｌ／Ｌ）耗竭细胞内钙池的钙，该效应消失，纳洛酮（１００μｍｏｌ／Ｌ），百日咳毒素（２００ｎｇ／Ｌ）处理８—１０ｈ及ｐｒｏｃａｉｎｅ（２ｍｍｏｌ／Ｌ）都能阻断该效应。以上结果表明：亮啡肽诱导［Ｃａ２＋］ｉ升高是通过δ受体与百日咳毒素敏感的Ｇ蛋白耦联并诱导心肌细胞内钙释放所引起。

The mechanism underlying Leu-enkephalin (LEK) induced increase of the intracellular concentration of free calcium ([Ca2+]i) in rat ventricular myocytes was investigated by using fura-2 AM as a calcium indicator. The results were as follows: LEK (60 μmol/L) elevated [Ca2+]i in ventricular myocytes no matter whether extracellular calcium was removed or not. However, the effect was no longer observed when the calcium in the intracellular pool was depleted by caffeine (5 mmol/L). The LEK effect could also be blocked by naloxone (100 μmol/L), pretreatment of the cells with PTX (200ng/L) 8- 10h or procain (2 mmol/L). The results suggest that the LEK effect is mediated by coupling of G-protein with δ-receptor that induced Ca2+ release from the intracellular pool in myocytes.