Diuretic effect of NG-nitro-L-arginine methyl ester in the rat

Intravenous infusion of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, L-NAME (10 micrograms kg-1 min-1), to anaesthetized rats produced a diuresis and natriuresis. By contrast, infusion of the same dose of NG-nitro-D-arginine methyl ester had no effect on either urine output or sodium excretion. The effects of L-NAME were first evident 120 min after the start of infusion and by 170 min a fivefold increase in urine volume and sodium excretion was recorded. L-NAME also produced a transient fall in inulin clearance and a persistent decline in renal blood flow. These renal effects of L-NAME were associated with a gradual elevation of mean arterial blood pressure, although this only attained statistical significance, in comparison with saline-infused animals, 170 min after the start of infusion. The findings indicate the diuresis and natriuresis evoked by L-NAME in the rat is a result of a direct tubular action together with a pressure diuresis.