Role of mito-KATP channel in pinacidil postconditioning-induced reduction of myocardial ischemia-reperfusion injury in rats: an in vitro experiment

Objective To evaluate the role of mitochondrial KATP (mito-KATP) channel in pinacidil postconditioning-induced reduction of myocardial ischemia-reperfusion (I/R) injury in rats. Methods SPF healthy male Sprague-Dawley rats, aged 16-20 weeks, weighing 250-300 g, were anesthetized with pentobarbital.Their hearts were excised and perfused in a Langendorff apparatus with K-H solution saturated with 95% O2-5% CO2 at 36.5-37.5 ℃.Thirty-two Langendorff-perfused hearts were divided into 4 groups (n=8 each) using a random number table: control group (group C), group I/R, pinacidil postconditioning group (group P) and 5-hydroxy decanoic acid plus pinacidil postconditioning group (group 5-HD+ P). Myocardial ischemia was induced by interrupting perfusion for 40 min followed by 60 min reperfusion.Immediately after onset of reperfusion, hearts were perfused with K-H solution containing 50 μmol/L pinacidil for 2 min and then with K-H solution for 58 min in group P, hearts were perfused with K-H solution containing 100 μmol/L 5-HD for 5 min, with K-H solution containing 50 μmol/L pinacidil for 2 min and then with K-H solution for 53 min in group 5-HD+ P.The heart rate (HR), left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP) and the maximum rate of increase in left ventricular pressure (+ dp/dtmax) were recorded at 20 min of equilibration (T1) and at the end of reperfusion(T2). Myocardial tissues were obtained at T2 for determination of myocardial infarct size and for examination of myocardial ultrastructure and Flameng scoring of the mitochondria was performed. Results Compared with group C, the HR, LVDP and + dp/dtmax were significantly decreased, and the LVEDP, myocardial infarct size and mitochondrial Flameng score were increased at T2 in group I/R (P 0.05). Compared with group P, the HR, LVDP and + dp/dtmax were significantly decreased and the LVEDP, myocardial infarct size and mitochondrial Flameng score were increased at T2 (P<0.05), and the pathological changes of myocardium were accentuated in group 5-HD+ P. Conclusion The whole mechanism by which pinacidil postconditioning reduces myocardial I/R injury is related to promoting opening of mito-KATP channel in rats. Key words: Myocardial reperfusion injury; Pinacidil; Mitochondria; KATP channels