The present study examines the effect of glutamine infusion on the interorgan fluxes of glutamine, alanine, urea, and ammonia with progressive fasting. Experiments were carried out in two groups of conscious dogs with catheters previously implanted in an artery and in the hepatic, portal, and renal veins. Group I (n = 12) was fasted for 24 h, and group II (n = 10) was fasted for 96 h. On the day of the study, seven animals of group I and five of group II received a constant infusion of glutamine (3.0 μmol·kg-1·min-1) for 1 h, and the rest (controls) received saline. Four-day fasting produced ketosis with a compensated metabolic acidosis. The demand for glutamine by the kidneys and gut increased, and the liver switched from net glutamine utilization to that of net production. The kidneys (33%) and gut (230%) increased their production of ammonia, while their release of alanine decreased. The estimated efflux of glutamine by skeletal muscle, however, did not change. All of the infused glutamine was cleared by the splanchnic and renal tissues. In group I, there was increased gut production of alanine, which was matched by increased hepatic alanine uptake and urea production. No such changes were observed in Group II. There was, however, an increase in hepatic uptake of ammonia. Finally, glutamine infusion did not alter glutamine or alanine output by skeletal muscle in group I, while it decreased efflux of alanine but not that of glutamine in group II. The data emphasize the complex interdependence of the liver, gut, kidneys, and skeletal muscle in nitrogen sparing. With fasting the liver switches from net glutamine utilization to that of production, while skeletal muscle does not enhance its production of glutamine. These changes are most likely a result of the enhanced ammoniagenesis in the kidneys and gut. In addition the data underscore the importance of glutamine as a nutritional supplement during periods of excessive catabolism.
|Original language||English (US)|
|Journal||American Journal of Physiology - Endocrinology and Metabolism|
|State||Published - Sep 18 1986|
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Physiology (medical)