Role of endothelium-derived nitric oxide in the renal hemodynamic response to amino acid infusion

Abstract

The present study was performed in anesthetized rats to compare the renal hemodynamic responses to mixed amino acids (M-AA) with those to L-arginine (L-Arg) and to examine the effect of endothelium-derived nitric oxide (EDNO) synthesis blockade on the M-AA-induced rise in renal plasma flow (RPF) and glomerular filtration rate (GFR). Intravenous infusion of both M-AA (Ser, Gly, Ala, and Pro, 0.71 mmol.100 g-1.min-1) and L-Arg (0.71 mmol.100 g-1.min-1) increased RPF and GFR. Peak increases in RPF for M-AA and L-Arg were 39.7% (P less than 0.05) and 63.4% (P less than 0.01), whereas GFR increases were 33.6% (P less than 0.05) and 46.7% (P less than 0.01, respectively). Outer cortical blood flow (OCBF) was increased with both treatments. Sodium excretion and urine flow were increased more with L-Arg than M-AA (both P less than 0.01). Infusion of the nitric oxide synthesis inhibitor, nitro-L-arginine (N-L-Arg, 20 micrograms.100 g-1.min-1) increased mean arterial pressure but decreased RPF 48.4% (P less than 0.001), OCBF 39.5% (P less than 0.001), GFR 37.8% (P less than 0.01), urine flow 29.8% (P less than 0.01), and sodium excretion 40.9% (P less than 0.01). When M-AA was administered after N-L-Arg, significant increases in OCBF, RPF, and GFR were observed (P less than 0.01); there was also an enhancement of sodium excretion and urine flow (both P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)