AJP - Renal Physiology, Vol 259, Issue 5 739-F746, Copyright © 1990 by American Physiological Society
Single-nephron responses to systemic administration of amino acids in dogs
S. A. Brown and L. G. Navar
Nephrology Research and Training Center, University of Alabama, Birmingham 35294.
It has been suggested that the tubuloglomerular feedback (TGF) system is
responsible for renal vasodilation during systemic infusion of amino acid
solutions. We evaluated the effect of intravenous administration of amino
acids (serine, alanine, proline, and glycine; total dose of 0.075 mmol of
amino acids.kg body wt-1.min-1) on whole kidney and single-nephron
hemodynamics in pentobarbital sodium-anesthetized dogs. At spontaneous
renal arterial pressure (RAP; 125.4 +/- 4.7 mmHg), measurements of
single-nephron function obtained during tubular blockade, stop-flow
pressure (SFP; 48.2 +/- 2.0 vs. 58.9 +/- 2.3 mmHg, P less than 0.01), and
proximally determined single-nephron glomerular filtration rate (SNGFR-TPC;
73.9 +/- 7.0 vs. 93.4 +/- 7.6 nl/min, P less than 0.01) increased in
parallel to the increases of outer cortical blood flow (OCBF; 15.4 +/- 1.1
vs. 19.1 +/- 1.5 units, P less than 0.05), renal blood flow (RBF; 4.60 +/-
0.18 vs. 5.73 +/- 0.22 ml.min-1.g kidney wt-1, P less than 0.01), and
glomerular filtration rate (GFR; 0.885 +/- 0.034 vs. 1.116 +/- 0.034
ml.min-1.g kidney wt-1, P less than 0.01). Free-flow tubular
fluid-to-plasma inulin ratios, determined from late proximal recollections
during saline (control) and amino acid infusions failed to provide evidence
for altered proximal reabsorption rate (1.63 +/- 0.12 vs. 1.58 +/- 0.17
during amino acids, NS). At reduced RAP (92.6 +/- 1.9 mmHg), where it is
presumed that TGF-mediated vasodilation is already near maximal, the
vasodilatory response to amino acid infusion was intact and single-nephron
parameters measured during tubular blockade increased to the same extent as
OCBF, RBF, and GFR.(ABSTRACT TRUNCATED AT 250 WORDS)
