EFFECTS OF L-ARGININE ON SYSTEMIC AND RENAL HEMODYNAMICS IN CONSCIOUS DOGS

1. The effects of L-arginine on systemic and renal haemodynamics were investigated in conscious dogs. L-Arginine was administered intravenously at doses of 15 and 75-mu-mol min-1 kg-1 for 20 min. 2. Mean arterial blood pressure, heart rate and cardiac output were not changed significantly by L-arginine infusion. However, L-arginine infusion induced a significant elevation of renal blood flow from 50 +/- 3 to 94 +/- 12 ml/min (means +/- SEM, P < 0.01). 3. Simultaneous infusion of N(G)-monomethyl-L-arginine (0.5-mu-mol min-1 kg-1) significantly inhibited the increase in renal blood flow produced by L-arginine (15-mu-mol min-1 kg-1) without significant changes in mean arterial blood pressure or heart rate. 4. Pretreatment with atropine completely inhibited the L-arginine-induced increase in renal blood flow, whereas pretreatment with indomethacin attenuated it (63 +/- 4 versus 82 +/- 10 ml/min, P < 0.05). 5. A continuous infusion of L-arginine increased renal blood flow in the intact kidney (55 +/- 3 versus 85 +/- 9 ml/min. P < 0.05), but not in the contralateral denervated kidney (58 +/- 3 versus 56 +/- 4 ml/min, P > 0.05). 6. These results suggest that intravenously administered L-arginine produces an elevation of renal blood flow, which may be mediated by facilitation of endogenous acetylcholine-induced release of endothelium-derived relaxing factor and vasodilatory prostaglandins.