The role of oxidation in the renal metabolism of glutamine by rat kidney tubules in vitro.

The metabolism of cold and 14C-[U]-glutamine in isolated kidney tubules of normal rats was studied in vitro to establish the relative importance of glucose synthesis and complete oxidation to CO2 for the metabolism of this amino acid in vitro. These metabolic fates were estimated by drawing a complete balance of the nitrogens and of the carbon chains of the extracted glutamine and studying the formation of 14CO2 from 14C-glutamine. It was found that glucose production constitutes the major fate for glutamine metabolism with 1 mM glutamine and that glutamine oxidation constitutes less than 20% of the metabolic fate of the carbon skeleton of this amino acid. With 5 or 10 mM glutamine however, the maximal oxidation to CO2 becomes more important (25%).