Role of catalase in metabolism of hydrogen peroxide by the perfused rat heart

Cardiac metabolism of H₂O₂ was studied by determining the concentration dependence for H₂O₂-stimulated release of GSSG, an indicator for flux through the glutathione peroxidase pathway, in perfused heart preparations. Treatment of rats with aminotriazole in vivo inhibited heart catalase by 83% and shifted the doseresponse curve for GSSG release toward lower H₂O₂ concentrations. In aminotriazole-treated rats, 50 μM H₂O₂ elicited a maximal rate of GSSG release (about 5 nmol per g heart), whereas 200 μM H₂O₂ was necessary for obtaining a similar rate of GSSG release in control rat hearts. The results show that catalase, although present at low levels of activity in the heart compared to other organs, functions as a major route for detoxication of H₂O₂ in the myocardium.