MODULATION OF GLUTATHIONE AND GLUTATHIONE-DEPENDENT ANTIOXIDANT ENZYMES IN MOUSE HEART FOLLOWING DOXORUBICIN THERAPY

The toxicity of the antineoplastic agent doxorubicin (DOX) has been sh own to be moderated by the antioxidant enzyme glutathione peroxidase. It has been reported that acute doses of DOX can cause an inhibition o f glutathione peroxidase in cardiac tissue, that may render this tissu e especially susceptible to further prooxidant damage. In this study, multiple DOX treatments at a therapeutic dose were assessed for their effect on the antioxidant enzyme status of cardiac and kidney tissue. DOX was administered i.p. (5 mg/kg) once a week for two weeks to male balb/c mice. The activities of the antioxidant enzymes superoxide dism utase (SOD), catalase (CAT), glutathione peroxidase (GPOX) and glutath ione reductase (GR) were measured 1, 2 and 7 days following the second DOX treatment in both heart and kidney. Levels of reduced glutathione (GSH) were also measured in cardiac tissue at these same times. Cardi ac levels of GPOX and GR showed a time-dependent decrease in activity, with 10% and 12% inhibition for GPOX and GR, respectively, at 7 days post second treatment. Cardiac levels of GSH also showed a significant decrease, approximately 15%, at 7 days post second treatment. Cardiac levels of SOD and CAT as well as kidney levels of all four antioxidan t enzymes were not affected by DOX treatment. These data suggest that DOX given in a therapeutic regimen, at a therapeutic dose, can cause d ecreases in cardiac levels of GPOX, GR and GSH that could render the h eart especially susceptible to further oxidative challenge.