Role of mitochondrial ATP-sensitive potassium channel in reduction of myocardial ischemia-reperfusion injury by calcitonin gene-related peptide in rats: an in vitro experiment

Objective To evaluate the role of the mitochondrial ATP-sensitive potassium (mito-KATP) channel in reduction of myocardial ischemia-reperfusion (I/R) injury by calcitonin gene-related peptide (CGRP) in rats in an in vitro experiment. Methods Healthy adult male Sprague-Dawley rats, weighing 250-300 g, were used in this study.After the animals were anesthetized, their hearts were immediately removed and retrogradely perfused with oxygenated K-H solution at 37 ℃ in a Langendorff apparatus.Twenty-four isolated rat hearts were assigned into 4 groups (n=6 each) using a random number table: control group (C group), I/R group, CGRP group and 5-hydroxydecanoate (5-HD) group.The hearts were first perfused with K-H solution for 30 min in the three groups.The hearts were continuously perfused with K-H solution for 150 min in group C. The hearts were subjected to ischemia for 30 min followed by 120 min of reperfusion to establish the model of myocardial I/R injury.In group CGRP, after the hearts were perfused with K-H solution for 10 min, 10-8 mol/L CGRP was infused for 20 min at a rate of 0.5 ml/min via the aorta, and then the model of myocardial I/R injury was established.In 5-HD group, specific mito-KATP channel blocker 5-HD 100 μmol/L was infused for 10 min at a rate of 0.5 ml/min via the aorta, and the other treatments were similar to those previously described in CGRP group.At the end of equilibration and 30, 60, 90 and 120 min of reperfusion, heart rate (HR), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and the maximum rate of increase or decrease in left ventricular pressure (±dp/dtmax) were recorded.The myocardial infarct size was measured by 2, 3, 5-triphenyltetrazolium chloride staining at 120 min of reperfusion. Results Compared with C group, HR, LVSP and ±dp/dtmax were significantly decreased and LVEDP was increased during reperfusion, and the percentage of myocardial infarct size was increased at 120 min of reperfusion in the other three groups (P<0.05). Compared with I/R group, HR, LVSP and ±dp/dtmax were significantly increased and LVEDP was decreased during reperfusion, and the percentage of myocardial infarct size was decreased at 120 min of reperfusion in CGRP group (P<0.05). Compared with CGRP group, HR, LVSP and ±dp/dtmax were significantly decreased and LVEDP was increased during reperfusion, and the percentage of myocardial infarct size was increased at 120 min of reperfusion in 5-HD group (P<0.05). Conclusion Opening of mito-KATP channels is involved in CGRP-induced reduction of myocardial I/R injury in rats in an in vitro experiment. Key words: Calcitonin gene-related peptide; Myocardial reperfusion injury; Mitochondria; KATP channels