EFFECT OF L-ARGININE ON ADRENAL AND RENAL BLOOD FLOWS DURING HEMORRHAGE IN CATS

Our earlier studies have shown development of indothelial dysfunction in the feline renal artery during hemorrhagic hypotension. Because L-a rginine (L-Arg), the precursor of nitric oxide (NO), reportedly improv es endothelial function in several pathophysiological slates including hypotension, we investigated its possible beneficial effect on the ad renal and renal circulations during hemorrhagic hypotension in anesthe tized, ventilated cats. Hypotension (mean arterial pressure 50 mm Hg) significantly increased vascular resistance and decreased blood flow ( radiolabeled microspheres) in both adrenal and renal cortices. L-Arg ( 30 mg/kg bolus, 10 mg/kg/min infusion, i.v.) had no significant hemody namic effects in normotension but prevented the increase of the vascul ar resistance and improved blood flow in the adrenal cortex during hyp otension. In the kidney, L-Arg also prevented hemorrhage-induced vasoc onstriction, although its effect on blood flow did not reach significa nce. The NO synthase inhibitor N-G-nitro-L-arginine (30 mg/kg bolus, 1 mg/kg/min infusion, i.v.) increased adrenal and renal vascular resist ances to a similar extent as that observed during hypotension. It thus seems that an L-Arg-reversible dysfunction of the endothelial NO-synt hesizing pathway contributes to hemorrhage-induced adrenal and renal v asoconstriction.