Evaluation of the effects of normobaric hyperoxia pretreatment on ischemia-reperfusion injury in a regional ischemia model using isolated rat heart

Introduction: Recent studies have shown beneficial effects of hyperoxia pretreatment (HOP) against ischemia-reperfusion injury in different organs. The aim of the present study was to investigate the effect of early and late phases of preconditioning induced by normobaric hyperoxia (>= 95% O2) on ischemia-reperfusion injury in isolated rat heart. Methods: Following 60 and 180 minutes of hyperoxia, rat hearts were isolated immediately (HOP60 and HOP180) or after 24 hours (HOP60/24 and HOP180/24), and were subjected to 30 minutes of regional ischemia followed by 120 minutes of reperfusion. Incidence and severity of ventricular arrhythmias, mechanical function of the heart and coronary flow were assessed during 120 min of reperfusion. LDH and CK release into the coronary effluent were measured. Infarct size also was calculated by triphenyl tetrazolium chloride staining at the end of reperfusion. Results: Incidence and severity of reperfusion arrhythmias were significantly reduced after hyperoxia pretreatment, especially in the early phase of treatment. Hyperoxia improves mycardial contractile function and decreases coronary flow reduction during reperfusion. Infarct size and enzymes release were also significantly decreased in the early and late phases of hyperoxia pretreatment. Conclusion: These results indicate that hyperoxia pretreatment before induction of regional heart ischemia reduces cardiac infarct size and attenuates reperfusion induced arrhythmias in isolated rat heart.