Nitric oxide: a potential mediator of amino acid-induced renal hyperemia and hyperfiltration

The role of nitric oxide in the modulation of systemic and renal hemodynamics was examined by using N omega-monomethyl-L-arginine (L-NMMA, 110 micrograms/kg/min), a competitive inhibitor of the conversion of L-arginine to nitric oxide. L-NMMA or saline vehicle (9.6 microL/min) was infused intravenously into anesthetized euvolemic Munich-Wistar rats. After 30 min, L-NMMA resulted in a uniform increase in mean arterial blood pressure (111 +/- 1 to 128 +/- 2 mmHg; P less than 0.05) and a modest reduction in renal plasma flow rate (4.4 +/- 0.2 to 4.2 +/- 0.1 mL/min; P less than 0.05), without change in glomerular filtration rate (1.16 +/- 0.03 to 1.15 +/- 0.03 mL/min); vehicle had no effect on these renal parameters. These rats were then subdivided to receive an intravenous infusion (37 microL/min) of either 10% glycine, 11.4% mixed amino acids, or equiosmolar dextrose. L-NMMA pretreatment markedly attenuated glycine-induced hyperfiltration (10 +/- 6 versus 33 +/- 5%, L-NMMA versus vehicle; P less than 0.05) and obliterated the renal hyperemic response (-7 +/- 6 versus 16 +/- 4%, L-NMMA versus vehicle; P less than 0.05). L-NMMA also caused modest blunting of the mixed amino acid-induced hyperfiltration (18 +/- 4 versus 30 +/- 4%, L-NMMA versus vehicle; P = 0.056) but failed to curtail the renal hyperemia (16 +/- 6 versus 20 +/- 4%). Dextrose had no effect on glomerular filtration rate or renal plasma flow.(ABSTRACT TRUNCATED AT 250 WORDS)