Effect of exogenous hydrogen peroxide on myocardial function and structure in isolated rat heart.

A time- and dose-dependent effect of exogenous hydrogen peroxide was determined on myocardial function, structure, high energy phosphate and lipid peroxidation in the isolated perfused rat heart. Hydrogen peroxide induced a dose-dependent decrease in cardiac function whereas 200 microM hydrogen peroxide reduced +dP/dt to 50% of control value after 10 mins. The effect of 300 microM hydrogen peroxide was more severe after 15 mins; changes observed with this dose were reversible within 10 mins of perfusion, becoming irreversible after 15 mins. Lipid peroxidation and severe morphological damage were observed after 10 mins of perfusion with 300 microM hydrogen peroxide. When 16 mEq potassium ions were added in the perfusion buffer during hydrogen peroxide perfusion, the degree of tissue damage and loss of ATP were attenuated. However, lipid peroxidation was not inhibited by high potassium ions. When 0.25 microM N,N'-diphenyl-1,4-phenylenediamine, a potent antioxidant, was added to the perfusate, lipid peroxidation was totally inhibited and the degree of tissue damage was decreased. However, depletion of tissue ATP and functional deterioration were not influenced. These results suggest that hydrogen peroxide-mediated ATP loss was independent of lipid peroxidation.