The aim of the study was to determine the role of both an inducible isoform of heme oxygenase (HO-1) and products of heme catabolism (carbon monoxide (CO), cardiac bilirubin and Fe2+) in protecting myocardium against post-ischemic myocardial dysfunction. Rat hearts were isolated and perfused according to the Langendorff technique to evaluate the recovery of myocardial function after total ischemia (20 min) and reperfusion (40 min) and production of reactive oxygen forms at a reperfusion phase. Ischemia/reperfusion caused impairment in myocardial function: left ventricular developing pressure (LVDP) was shown to be decreased, while end-diastolic pressure (EDP) and both coronary perfusion pressure and coronary resistance increased. Free oxygen radicals were generated at the reperfusion phase which led to injuries to cardiomyocytes and creatine kinase efflux into perfusate. We have found that upregulation of HO-1 by preliminary (24 h before ischemia) injections of 25 mg/kg hemin (i.p.) resulted in improving the myocardial function due to increasing the enzyme activity and forming the cardial bilirubine, while generation of reactive oxygen forms was inhibited, as well as the contents of creatine kinase reduced. As a result, impairment in cardiomyocytes diminished, and coronary vessels dilated to improve the functional parametres of the heart work.