Chronic inhibition of nitric oxide synthesis in rats increases aortic superoxide anion production via the action of angiotensin II

Objective: Chronic inhibition of nitric oxide (NO) synthesis by N(w)-nitro-L-arginine methyl ester (L-NAME) increases vascular tissue angiotensin II activity and oxidative stress in animals by incompletely understood mechanisms. In a rat model, we investigated the role of local angiotensin II activity in the pathogenesis of increased oxidative stress. Design: We studied the aortas of control rats and others receiving L-NAME or L-NAME plus an angiotensin II type 1 receptor antagonist (CS-866). Results: Administration of L-NAME for 7 days significantly increased superoxide anion (O₂^-) and both immunoreactivity and electrophoretically demonstrable activity of redox-sensitive transcription factors (NF-κB and AP-1). Treatment with the angiotensin II type 1 receptor antagonist prevented all of the above changes. The observed effects of the type 1 receptor antagonist was independent of the L-NAME-induced arterial hypertension. Conclusions: These findings suggest that chronic inhibition of NO synthesis may increase vascular oxidative stress and oxidative stress-sensitive signals via the action of angiotensin II mediated via type 1 receptors. (C) 2000 Lippincott Williams and Wilkins.