Enteral glutamate is almost completely metabolized in first pass by
the gastrointestinal tract of infant pigs.
Reeds, Peter J., Douglas G. Burrin, Farook Jahoor, Linda Wykes, Joseph
Henry & Elizabeth M. Frazer.
USDA/ARS Children's Nutrition Research Center, Department of
Pediatrics, Baylor College of Medicine, 1100, Bates Street, Houston,
TX 77030
APStracts 2:0206E, 1995.
We studied the absorption of enteral glutamate and phenylalanine using
isotopic-tracer and arteriovenous-difference techniques. Six piglets,
implanted with portal, carotid and gastric catheters and an
ultrasonic portal flow probe, received a 6-h intragastric infu sion
of [U13C]-glutamate and [2H]-phenylalanine, with a high-protein diet
offered once hourly. Amino acid concentrations and the isotopic
enrichments of all mass isotopomers of glutamate, glutamine and
phenylalanine were measured in portal and arterial blood over the
last hour. There was significant (P<0.025) net absorption of the
indispensable amino acids as well as arginine, proline, serine and
alanine. There was no portal uptake of glutamate, aspartate and
glycine and arterial glutamine was re moved by the portal drained
viscera (P<0.05). At isotopic steady state 72% of the 2[H]
-phenylalanine but only 5% of the [U13C]-glutamate tracer appeared in
the portal blood. We conclude that in fed infant pigs, the gut
metabolizes virtually all the enteral glutamate during absorption.
Therefore glutamate and glutamine in the body as a whole must derive
almost entirely from synthesis de novo.
Received 30 June 1995; accepted in final form 21 September 1995.
APS Manuscript Number E304-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95