The administration of oxytocin during early reperfusion, dose-dependently protects the isolated male rat heart against ischemia/reperfusion injury

Abstract

In our previous study, the administration of oxytocin (OT) could precondition the heart against ischemia/reperfusion injury. In this study, to investigate the cardiac postconditioning effect of oxytocin, isolated rat hearts were mounted on a Langendorff perfusion apparatus. In all groups, the hearts underwent 30min of regional ischemia followed by 120min of reperfusion. In the ischemia/reperfusion (IR) group, ischemia and reperfusion was induced. In the ischemic postconditioning (Ipost) group, hearts underwent 6cycles of 10s reperfusion and 10s ischemia at the beginning of reperfusion. In the other groups (III-IX), OT was perfused 5min before the onset of reperfusion and continued for 25min with following doses (Molar): 10−12, 5×10−12, 8×10−12, 10−11, 2×10−11, 5×10−11, and 10−10. The infarct size and coronary effluent levels of creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH) and malondialdehyde (MDA) were calculated at the end of reperfusion. The infarct size decreased considerably in Ipost group compared to IR group (P<0.05). Also, the infusion of oxytocin by doses of 8×10−12M, 10−11M and 2×10−11M dose-dependently reduced infarct size (P<0.05) significantly compared to the IR group. LDH level in coronary effluent was markedly decreased in Ipost group and treatment with oxytocin by doses of 8×10−12M, 10−11M, 2×10−11M and 5×10−11M (P<0.05) compared to IR group. Ipost, OT 2×10−11and 10−11M significantly decreased CK-MB level (P<0.05). Ipost, OT 8×10−12, 10−11 and 2×10−11M significantly decreased MDA level as compared to IR group. Our study shows that oxytocin dose-dependently exerts cardiac postconditioning.