Urea cycle intermediate kinetics and nitrate excretion at normal
and "therapeutic" intakes of arginine in man.
Beaumier, Louis, Leticia Castillo, Alfred M. Ajami, Vernon. R. Young.
Laboratory of Human Nutrition and Clinical Research Center,
Massachusetts Institute of Technology, Cambridge, MA 02139; Shriners
Burns Institute and Trauma Service and Massachusetts General
Hospital, Boston, MA 02114; MassTrace Inc., Woburn, MA 01801.
APStracts 2:0138E, 1995.
We investigated the effects of a high dietary supplement of arginine
on plasma arginine, ornithine and leucine kinetics and on urea
production and excretion in five healthy young adult men. Subjects
received either 56 or 561 mg arginine kg-1 d-1 for six days, via a
complete l-amino acid diet, and on day seven a tracer protocol (first
3h fast; next 5h fed) conducted, involving primed, constant
intragastric infusions of L-[15N,15N-guanidino, 5,5-2H2] arginine, L
-[5-13C]ornithine, L-[5,5,5-2H3]leucine and [15N,15N]urea, with a
prime of 13C-bicarbonate. Plasma arginine and ornithine fluxes
increased significantly (p < 0.05) with arginine
supplementation, as did the rate of conversion of plasma labeled
arginine to ornithine (p < 0.05) and rate of ornithine oxidation
(p < 0.001). However, absolute changes in ornithine kinetics
were less than those for arginine or those based on changes expected
from the change in arginine intake, implying a complex
compartmentation in both whole body arginine and ornithine
metabolism. The plasma nitrate concentration, daily output of total
NO3 and conversion of 15N-arginine to nitrate did not differ between
the diets. Urea production and urea excretion were reduced
significantly with arginine supplementation, suggesting an anabolic
effect on the whole body nitrogen economy, possibly via the raised
plasma insulin levels (p = 0.013) during the prandial phase.
Received 8 March 1995; accepted in final form 15 June 1995.
APS Manuscript Number E108-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.