Quantification of the incorporation of 15n-ammonia into plasma amino acids and urea. Patterson, Bruce W., Fabio Carraro, Samuel Klein, and Robert R. Wolfe. Departments of Surgery, Anesthesiology, and Internal Medicine, The University of Texas Medical Branch and the Metabolism Unit, Shriners Burns Institute, Galveston, TX
APStracts 2:0082E, 1995.
The incorporation of 15N into individual plasma amino acids and urea was quantified in 5 human subjects who received 15NH4Cl either orally or intravenously for 6 h. Following oral tracer administration the highest enrichments was achieved by arginine, followed by urea and glutamine; distribution of 15N within glutamine was 55% amide / 45% amino N. Glutamine achieved the highest enrichment following the intravenous administration of tracer with a distribution of 92% amide / 8% amino N. The relative distribution pattern of 15N incorporation was quantified from the rate at which 15N initially appeared in each plasma component. Amino acids (especially arginine, glutamine, and glutamate) accounted for greater than half (54%) of the orally -administered tracer which was initially recovered in plasma components, compared to 46% initial appearance for urea; for the intravenous tracer, amino acids accounted for 78% of initial appearance of tracer compared to 22% for urea. Our results highlight the involvement of the splanchnic bed in the utilization of orally -administered ammonia (preferential incorporation of oral tracer into arginine, urea, glutamate, and the amino N of glutamine) in contrast to the preferential incorporation of systemically-administered ammonia into the amide N of glutamine and alanine. 

Received 22 September 1994; accepted in final form 17 April 1995.
APS Manuscript Number E391-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.