Background: Creatine kinase is a cardiac biomarker that is used for the assessment of ischemic injuries and myocardial infarction. The present study was designed to evaluate effects of oxytocin administration during ischemia and reperfusion periods on CK-MB levels in the coronary effluent of isolated rat heart and the possible role of oxytocin receptor, nitric oxide (NO), prostacyclin and mitochondrial ATP-dependent potassium channels in this regard.

Methods: Male wistar rats (n=8) were anesthetized with sodium thiopental and their hearts were transferred to a Langendorff perfusion apparatus. All animals were randomly divided into nine groups as follow; in the ischemia-reperfusion group, hearts underwent 30 min of regional ischemia followed by 120 min of reperfusion. In oxytocin group, hearts were perfused with oxytocin 5 min after ischemia induction for 25 min. In other groups, 35 min prior to oxytocin perfusion, atosiban (a non-specific oxytocin receptor blocker), L-NAME (an NO synthase inhibitor), indomethacin (a non-specific cyclooxygenase blocker) and 5-HD (a specific mKATP channel blocker) were perfused for 10 min. In all groups, we measured CK-MB levels in the coronary effluent at the end of reperfusion. Moreover, coronary flow (mL/min) was measured at baseline, during ischemia period and 60 and 120 min after reperfusion.

Results: Oxytocin administration significantly reduced CK-MB level in oxytocin group as compared to ischemia-reperfusion group. Administration of atosiban, L-NAME, indomethacin and 5-HD prior to oxytocin perfusion abolished the effects of oxytocin on CK-MB levels.

Conclusion: Administration of oxytocin during ischemia and reperfusion periods deceased CK-MB levels but infusion of atosiban, L-NAME, 5-HD and indomethacin inhibited oxytocin from exerting its effects.