UPTAKE AND METABOLISM OF GLUTAMINE IN CULTURED KIDNEY-CELLS

In cultured rat kidney cells, glutamine utilization and product formation were followed as a function of time at either 10 .mu.M or 1 mM initial glutamine concentration. At 1 mM glutamine, glutamate and .gamma.-glutamylglutamate were the major products formed at the end of a 5-min incubation period; glutamate accounted for 46% while .gamma.-glutamylglutamate accounted for 33% of the glutamine utilized. With time, glutamate continued to accumulate while .gamma.-glutamyl peptide formation leveled off. The role of .gamma.-glutamyl transpeptidase was assessed by using hippurate, a physiological activator of .gamma.-glutamyl transpeptidase and acivicin, L-(.alpha.S,5S)-.alpha.-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid, an inhibitor of .gamma.-glutamyl transpeptidase. Hippurate, 4 mM, increased the utilization of glutamine and the formation of glutamate, .gamma.-glutamyl peptides and ammonia. Exposure of cells to acivicin resulted in 98% inhibition of .gamma.-glytamyl transpeptidase without affecting phosphate-dependent glutaminase activity. Acivicin inhibition resulted in a decreased utilization of glutamine and product formation as compared to control; 5-oxoproline appearance fell 70%. The fractional distribution of glutamine C and N into its metabolic products in control, hippurate and acivicin-treated cells showed no change at the end of 60 min. .gamma.-Glutamyl transpeptidases may utilize glutamine and forms .gamma.-glutamyl peptides in cultured kidney cells.