EFFECT OF GLUTAMINE ON PROTEIN-SYNTHESIS IN ISOLATED INTESTINAL EPITHELIAL-CELLS

The influence of glutamine on protein synthesis in small-bowel enteroc ytes was tested. Enterocytes were isolated from different levels of th e villi of rat jejunum and were incubated in the presence of different glutamine concentrations, up to 3.4 mmol/L. Protein synthesis was det ermined by measuring incorporation of H-3-phenylalanine into trichloro acetic acid-precipitated proteins. Glutamine, but no other amino acids , stimulated protein synthesis in enterocytes from all levels of the v illi. A maximal effect was noted at a glutamine concentration of 0.67 mmol/L, which is the normal plasma concentration. The amino acid stimu lated the synthesis of both secreted and nonsecreted proteins. The sti mulatory effect of glutamine on protein synthesis was blocked by the g lutaminase inhibitor 6-diazo-5-oxo-L-norleucine and was duplicated by equimolar concentrations of acetoacetate or 3-hydroxybutyrate. The res ults suggest that glutamine stimulates protein synthesis in small-bowe l enterocytes and that this effect of glutamine is related to provisio n of energy. The findings are important because they suggest that incr eased protein synthesis may be one of the mechanisms by which glutamin e exerts its protective effect on gut mucosa during critical illness.