ROLE OF ENDOGENOUS ANGIOTENSIN-II IN RENAL HEMODYNAMIC AND EXCRETORY RESPONSES TO L-ARGININE INFUSION

The purpose of this study was to investigate whether endogenous angiot ensin II has a functional role in renal hemodynamic and excretory chan ges induced by L-arginine, a substrate for nitric oxide (NO), in anest hetized rats. During the intravenous infusion of L-arginine (50, 100, 200 pmol/kg . min), there was no significant change in systemic or ren al hemodynamics, but urine how and urinary sodium excretion markedly i ncreased in a dose-dependent manner. Simultaneously, L-arginine infusi on produced an increase in urinary excretion of NO metabolites, NO2- a nd NO3-. Treatment with L-158809 biphenyl-4-yl]methyl]-H-3-imidazo-[4, 5-b]pyridine} (0.3 mg/kg), a selective angiotensin II type I receptor antagonist, caused a reduction in mean arterial pressure, and a rise i n renal blood flow and glomerular filtration rate, with no changes in excretory responses. In the presence of L-158809, L-arginine-induced d iuretic and natriuretic actions were observed to the same extent as se en in the absence of L-158809. These data suggest that the infusion of L-arginine causes diuresis and natriuresis, possibly via the formatio n of nitric oxide in the kidney, and that endogenous angiotensin II is not involved in the L-arginine-induced renal actions.