Role of mitochondrial cardiolipin in the protective effects of diazoxide preconditioning on isolated rat hearts against ischemia-reperfuslon injury

Abstract

Objective To investigate the role of mitochondrial cardiolipin in the protective effects of diazoxide preconditioning on isolated rat hearts after ischemia-reperfusion (I/R).Methods Seventy-two healthy SD rats of both sexes (36 male,36 female) weighing 200-280 g were randomly divided into 4 groups ( n = 18 each): group Ⅰ control (group C);group Ⅱ I/R;group Ⅲ diazoxide preconditioning + I/R (group DZ+ I/R) and group Ⅳ 5-hydroxydeconoate (group 5-HD) + DZ + I/R (group 5-HD + DZ + I/R).The animals were anesthetized with intraperitoneal pentobarbital 40 mg/kg.Their hearts were excised and passively perfused in a Langendorff apparatus with oxygenated K-H solution at 5.8 kPa and 37℃.Left ventricular developed pressure (LVDP) was measured from a fluid filled latex balloon inserted in the left ventricle.After 20 min of stabilization the isolated hearts were subjected to 40 min ischemia followed by 30 min reperfusion in group Ⅱ .In group Ⅲ the isolated hearts were perfused with diazoxide 50 μmol/L for 10 min before I/R and in group Ⅳ the isolated hearts were perfused with 5-HD 100 μmol/L for 10 min before diazoxide preconditioning.HR,LVDP and left ventricular end-diastolic pressure (LVEDP) were recorded and mitochondrial cardiolipin content in myecardium was measured at the end of 20 min stabilization (T1,baseline),immediately before ischemia (T2) and at the end of 30 min reperfusion (T3) (6 animals at each time point).Results I/R significantly decreased HR and LVDP and increased LVEDP and decreased mitocbendrial cardiolipin content in myocardium at T3 as compared with the baseline values before ischemia at T1 and T2in group Ⅱ .Diazoxide preconditioning significantly attenuated the I/R induced effects.The protective effects of diazoxide preconditioning against I/R injury was counteracted by 5-HD,a specific mitochondrial ATP sensitive potassium channel blocker.Conclusion Diazoxide preconditioning can protect the myocardium against I/R injury via maintenance of mitochondrial cardiolipin content in myocardium. Key words: Diazoxide; Mitochondria,Heart; Reperfusion injury; Cardiolipins