Effect of ischemic postconditioning on mitochondrial cardiolipin synthesis during myocardial ischemia-reperfusion in rats in vitro

Abstract

Objective To evaluate the effects of ischemic postconditioning on mitochondrial cardiolipin synthesis during myocardial ischemia-reperfusion(I/R)in rats in vitro. Methods Healthy male Sprague-Dawley rats, aged 16-20 weeks, weighing 250-350 g, were used in the study.The animals were anesthetized with intraperitoneal pentobarbital sodium 40 mg/kg and received intraperitoneal heparin 250 U/kg.Their hearts were excised and retrogradely perfused in a Langendorff apparatus.Sixty-four isolated rat hearts were randomly divided into 4 groups(n=16 each)using a random number table: control group(group C), I/R group, ischemic postconditioning group(group IPO)and 5-hydroxydecanoate(5-HD)plus ischemic postconditioning group(group 5-HD + IPO). After 20 min of equilibration, the hearts were continuously perfused with K-H solution for 70 min in group C. In I/R group, after 20 min of equilibration, the hearts were continuously perfused with 4 ℃ ST.Thomas cardioplegic solution 10 ml/kg, and exposed to 40 min of ischemia followed by reperfusion with oxygenated K-H solution at 37 ℃ for 30 min.In group IPO, after 20 min of equilibration, the hearts were subjected to 6 cycles of 10 s reperfusion followed by 10 s ischemia starting from 40 min of ischemia, and then were reperfused with oxygenated K-H solution at 37 ℃ for 28 min.In group 5-HD+ IPO, after 20 min of equilibration, the hearts were perfused with K-H solution containing 100 μmol/L 5-HD(mitochondrial ATP-sensitive potassium channel blocker)for 5 min starting from 40 min of ischemia, and then the other procedures were similar to those previously described in group IPO.At 20 min of equilibration(T1)and 30 min of reperfusion(T2), HR, left ventricular developed pressure(LVDP), left ventricular end-diastolic pressure(LVEDP)and coronary flow(CF)were recorded.The coronary effluent 2 ml was collected for detection of lactic dehydrogenase(LDH)and creatine kinase(CK)activities.The mitochondria were extracted for determination of cardiolipin content. Results HR, LVDP, and CF were significantly lower, LVEDP was higher, and the LDH and CK activities in coronary effluent were higher at T2 than at T1 in the four groups.Compared with group C, HR, LVDP and CF were significantly decreased, LVEDP was increased, and the LDH and CK activities in coronary effluent were increased at T2 in the other three groups.Compared with I/R group, HR, LVDP and CF were significantly increased, LVEDP was decreased, and the LDH and CK activities in coronary effluent were decreased at T2 in IPO group.Compared with IPO group, HR, LVDP and CF were significantly decreased, LVEDP was increased, and the LDH and CK activities in coronary effluent were increased at T2 in 5-HD+ IPO group. Conclusion The mechanism by which ischemic postconditioning reduces myocardial I/R injury is related to opening of mitochondrial ATP sensitive potassium channels and increasing mitochondrial cardiolipin synthesis in rats. Key words: Myocardial reperfusion injury; Mitochondria; Cardiolipins; Ischemic postconditioning