This study examined the effects of enalapril treatment on L-NAME-induced hypertensive rats and oxidative profile in the heart. Four experimental groups were established: control (received water for three weeks); L-NAME (600 mg/L in drinking for three weeks); enalapril (20 mg/L in drinking two last weeks); L-NAME + enalapril, treated with L-NAME for one week, and L-NAME plus enalapril in the last two weeks. Arterial blood pressure, lipid peroxidation (TBARS and chemiluminescence-CL), and catalase, superoxide dismutase, glutathione peroxidase, and glutathione-S-transferase activities were evaluated. An increase by 47 % in the arterial blood pressure was observed in L-NAME-treated rats. Hypertension was reduced (9 %) with enalapril. Hypertension increased TBARS (177 %), CL (23 %), and glutathione peroxidase (31 %), this last, reducing by 11 % in L-NAME + enalapril group. Glutathione-Stransferase increased by 46 % in enalapril group. These results suggest that L-NAME administration increased arterial pressure and oxidative stress, indicating glutathione peroxidase as an important antioxidant in this model.Colegio de Farmacéuticos de la Provincia de Buenos Aire