Demonstration of hydroxyl radical and its role in hydrogen peroxide-induced myocardial injury: Hydroxyl radical dependent and independent mechanisms

We investigated the mechanism of hydrogen peroxide (H₂O₂) action on myocardial injury in relation to hydroxyl radical (OH) formation. Isolated rat hearts were perfused with a concentration of H₂O₂ (300 μM) known to produce cardiac injury. Perfusion of H₂O₂ for 15 min caused severe myocardial dysfunction, morphological damage. ATP depletion, and lipid peroxidation. Hydrogen peroxide concentration in the coronary effluent was reduced approximately 40% reflecting a myocardial H₂O₂ consumption of 12.7 ± 0.9 μmol/15 min/g wet tissue (n = 12). One of the OH-generated derivatives, 2,3-dihydroxybenzoic acid (2,3-DHBA), formed from reaction with salicylic acid, was detected in the coronary effluent by high-performance liquid chromatography at 23.16 ± 4.05 nmol/15 min/g wet tissue. Catalase (200 U/ml, n = 6) added to the perfusate attenuated all parameters of myocardial injury by eliminating H₂O₂ from the perfusate, and thus OH was not detected in the effluent. Deferoxamine (5 mM, n = 7) added to the perfusate reduced morphological damage and lipid peroxidation, but not dysfunction or ATP depletion. Deferoxamine significantly reduced OH production; 2,3-DHBA was 5.22 ± 3.56 nmol/15 min/g wet tissue. The present study provides evidence that OH is produced in the H₂O₂-perfused heart. The adverse H₂O₂-mediated myocardial outcomes documented in this study appear to arise from both OH-dependent mechanisms.