Effect of sevoflurane postconditioning on mitochondrial connexin 43 during myocardial ischemia-reperfusion in rats and the role of mito-KATP channels: an in vitro experiment

Abstract

Objective To investigate the effect of sevoflurane postconditioning on mitochondrial connexin 43 (Cx43) during myocardial ischemia-reperfusion (I/R) in isolated rat hearts and the role of mitochondrial ATP-sensitive potassium (mito-KATP) channels in it. Methods Forty-five adult male Sprague-Dawley rats, weighing 200-250 g, were used in the study.Their hearts were excised and retrogradely perfused with K-H solution in a Langendorff apparatus.The 45 isolated hearts were assigned into 5 groups (n=9 each) using a random number table: control group (group C), I/R group, sevoflurane postconditioning group (group Sev), and sevoflurane postconditioning plus 5-hydroxydecanoate (5-HD, a specific mito-KATP channel blocker) group (group Sev+ 5-HD) and I/R plus 5-HD group (group I/R+ 5-HD). The hearts were subjected to 20 min of global ischemia followed by 90 min of reperfusion to establish the model of myocardial I/R injury.From the beginning of reperfusion, the hearts were perfused with K-H solution saturated with 3% sevoflurane for 15 min in group Sev, with K-H solution saturated with 3% sevoflurane and containing 100 μmol/L 5-HD in group Sev+ 5-HD, and with K-H solution containing 100 μmol/L 5-HD in group 5-HD.The heart rate (HR), left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDP) and the maximum rate of increase and decrease of ventricular pressure (±dp/dtmax) were recorded at the end of equilibration (T1) and 30 and 60 min of reperfusion (T2, 3). At 90 min of reperfusion, the myocardial infarct size was measured by TTC staining, and the expression of total Cx43 (tCx43) and phosphorylated Cx43 (p-Cx43) in mitochondria was determined by Western blot analysis.The percentage of myocardial infarct size and p-Cx43/tCx43 ratio were calculated. Results Compared with group C, the HR, LVDP and ±dp/dtmax were significantly decreased, and the LVEDP was increased at T2, 3, and the percentage of myocardial infarct size was increased in the other 4 groups, the expression of mitochondrial tCx43 and p-Cx43 was significantly down-regulated in I/R, Sev+ 5-HD and 5-HD groups (P 0.05). Compared with group I/R, the HR, LVDP and ±dp/dtmax were significantly increased, and the LVEDP was decreased at T2, 3, the percentage of myocardial infarct size was decreased, and the expression of mitochondrial tCx43 and p-Cx43 was up-regulated in group Sev (P 0.05). Compared with group Sev, the HR, LVDP and ±dp/dtmax were significantly decreased, and the LVEDP was increased at T2, 3, the percentage of myocardial infarct size was increased, and the expression of mitochondrial tCx43 and p-Cx43 was down-regulated in group Sev+ 5-HD (P 0.05). Conclusion The mechanism by which sevoflurane postconditioning attenuates myocardial I/R injury may be related to induction of mito-KATP channel opening and up-regulation of the expression of mitochondrial Cx43 in cardiomyocytes of rats. Key words: Anesthetics, inhalation; Ischemic postconditioning; Myocardial reperfusion injury; Mitochondria; Connexin 43; KATP channels