Enteral Glutamine Modulates Renal Glutamine Utilization

Abstract

Enteral glutamine feeding effect on renal glutamine utilization was assessed from the perspective of gamma glutamyltransferase activity-dependent cellular glutamate modulation of phosphate-dependent glutaminase. After 4 d, rats fed an elemental diet supplemented with glutamine exhibited a 21% higher kidney glutamate content and 27% reduction in ammonium excretion, both P < 0.05. Glutamine removal from plasma was depressed 62% in the glutamine-fed group (324 ± 155 vs. 780 ± 154 nmol·min-1·100 g body weight-1, P < 0.05) despite an elevated arterial plasma glutamine load delivered to the kidney. Administration of acivicin, 36 mg/kg body weight, to glutamine-fed rats inhibited gamma glutamyltransferase > 90% and decreased kidney glutamate content 42%. This reduction in kidney glutamate was associated with a 3.3-fold enhancement in both glutamine extraction (474 ± 184 to 1548 ± 255 nmol·min-1·100 g body weight-1) and ammonium excretion (295 ± 30 to 978 ± 96 nmol·min-1·100 g body weight-1), both P < 0.01. These findings are consistent with enteral glutamine regulation of renal glutamine utilization through an elevation of the cellular glutamate level.