['To investigate whether cyclooxygenase-2 (COX-2) and heme oxygenase-1 (HO-1) are involved in the bradykinin-induced delayed protection.', 'Cardiac contractility, lactate dehydrogenase (LDH) and infarct area were analyzed in isolated rat hearts undergoing ischemia-reperfusion injury induced by Langendorff method.', 'Conscious rats received bradykinin (40 microg/kg), and the isolated hearts were subjected to 30 min of regional ischemia and 120 min of reperfusion 24 h later. Bradykinin pretreatment would improve post-ischemic performance, and reduced the release of LDH and infarct size. COX-2 inhibitor celecoxib (3 mg/kg) abolished bradykinin-induced protection, leading to poorer myocardial performance, release of more LDH and larger infarct sizes. Administration of HO-1 inhibitor ZnPP IX(20 microg/kg) before bradykinin partially abrogated the delayed protection. Pretreatment with the mitochondrial ATP sensitive potassium channel(mitoK(ATP) antagonist 5-HD before or 24 h after bradykinin administration also abolished the effect of protection.'] Are [ COX-2 and HO-1 involved in the delayed preconditioning elicited by bradykinin in rat hearts ]?