Dietary glutamine suppresses endogenous glutamine turnover in the rat

Plasma glutamine turnover was determined using 1-C-14-labeled glutamine in rats that consumed crystalline amino acid diets containing the equivalent o f 16% protein with 25% of the amino acids as glutamine or a control diet co ntaining no glutamine (or glutamate) for 10 days. Glutamine turnover in glu tamine-fed animals was 66% of the rate in the control group. Glutamine feed ing caused 20% higher levels of arterial plasma glutamine, Arterial-portal differences across the portal-drained viscera showed net glutamine uptake i n control animals but no net uptake or release in the glutamine-fed group. Skeletal muscle glutamine synthetase activity was similar in both groups. T he results indicate that long-term consumption of relatively large amounts of dietary glutamine decreases the turnover of plasma glutamine and thus re duces the need for endogenous glutamine synthesis. Copyright (C) 2000 by W. B. Saunders Company.