Renal amino acid metabolism during endotoxemia in the rat

Background. The kidney has an important function in the exchange of nitroge nous metabolites. Glutamine is the most important substrate for renal ammon iagenesis and thus plays a crucial role in acid-base homeostasis. Furthermo re, the kidney is the main endogenous source for de novo arginine productio n from citrulline, which in turn is derived from intestinal glutamine metab olism. Sepsis is a condition in which glutamine availability is reduced, wh ereas the need for arginine biosynthesis may be increased. Limited bioavail ability of glutamine may affect arginine synthesis, which may have conseque nces for nitric oxide (NO) synthesis. Therefore, we studied renal glutamine and arginine metabolism in a rat model of endotoxemia and related this to NO metabolism. Materials and methods. Rats were subject to double hit endotoxemia, and con trol rats received 0.9% NaCl. Renal blood how was measured using paraaminoh ippuric acid, Concentrations of plasma amino acids and nitrate were measure d in the aorta and renal vein to calculate net renal uptake or release of a mino acids and address NO production. Results. The arterial concentrations of glutamine and ammonia were not chan ged in endotoxemic rats. Although renal glutamine uptake was reduced, total renal ammonia production was not changed during endotoxemia. The arterial concentration of citrulline and renal citrulline uptake was not altered in endotoxin-treated rats, but renal arginine production was increased. Howeve r, no effect was observed on nitric oxide production. Conclusions. Although the kidney has very important functions in the excret ion of waste products and in interorgan metabolism, this study suggests tha t the kidney has a limited role in glutamine, arginine, and NO metabolism d uring late endotoxemia in rats. (C) 2000 Academic Press.