H. G. Windmueller, A. Spaeth
Dec 1, 1975
Citations
12
Influential Citations
341
Citations
Quality indicators
Journal
Archives of biochemistry and biophysics
Abstract
Abstract Only a small fraction of the l -[U-14C]glutamate (2%) and the l -[U-14C]glutamine (34%) administered at a 6 m m concentration into the lumen of rat jejunal segments in situ was recovered unchanged in venous blood collected from the segments. The remaining 14C of both amino acids was recovered in the blood as CO2 (60%), proline (5%), citrulline (4%), alanine (3%), ornithine (2%), and organic acids, mostly lactate (19%). The amide nitrogen of glutamine was recovered mostly as ammonia and the amino nitrogen of both amino acids predominantly in alanine. A nearly identical distribution of products was seen in previously published experiments in which rat intestine took up l -[U-14C]glutamine from arterial blood (Windmueller, H. G., and Spaeth, A. E. (1974) J. Biol. Chem., 249, 5070–5079). The results are therefore consistent with a single metabolic pool within mucosal cells for blood-derived and lumen-derived glutamine. When 6 m m glutamine was continuously perfused through the lumen, jejunal segments metabolized arterial and luminal glutamine at approximately equal rates (130–190 nmol min−1 (g of tissue)−1). The total combined rate was 1.7 times the rate of utilization of arterial glutamine alone in jejunal segments not absorbing glutamine. These results provide the first quantitative data on comparative metabolism by the intestine of substrates from the lumen and from blood. Rat intestine apparently metabolizes nearly all absorbed dietary glutamate and most glutamine in addition to circulating glutamine derived from other tissues.