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 my ocardial injury in relation to hydroxyl radical (.OH) formation. Isola ted rat hearts were perfused with a concentration of H2O2 (300 muM) kn own to produce cardiac injury. Perfusion of H2O2 for 15 min caused sev ere myocardial dysfunction, morphological damage, ATP depletion, and l ipid peroxidation. Hydrogen peroxide concentration in the coronary eff luent was reduced approximately 40% reflecting a myocardial H2O2 consu mption of 12.7 +/- 0.9 mumol/15 min/g wet tissue (n = 12). One of the .OH-generated derivatives, 2,3-dihydroxy-benzoic acid (2,3-DHBA), form ed from reaction with salicylic acid, was detected in the coronary eff luent 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 perfusat e attenuated all parameters of myocardial injury by eliminating H2O2 f rom the perfusate, and thus .OH was not detected in the effluent. Defe roxamine (5 mM, n = 7) added to the perfusate reduced morphological da mage and lipid peroxidation, but not dysfunction or ATP depletion. Def eroxamine significantly reduced .OH production; 2,3-DHBA was 5.22 +/- 3.56 nmol/15 min/g wet tissue. The present study provides evidence tha t .OH is produced in the H2O2-perfused heart. The adverse H2O2-mediate d myocardial outcomes documented in this study appear to arise from bo th .OH-dependent and .OH-independent mechanisms.