Effect of glutamine on glutathione kinetics in vivo in dogs.
To determine whether glutamine affects glutathione (GSH, gamma-glutamyl-cysteinyl-glycine) metabolism, seven healthy beagle dogs received 6-h infusions of [(15)N]glutamate and [(13)C]leucine after a 3-day fast. Isotope infusions were performed during oral feeding with an elemental regimen, supplemented with either l-glutamine or an isonitrogenous amino acid mixture, on two separate days and in randomized order. Timed blood samples were obtained, and a surgical duodenal biopsy was performed after 6 h of isotope infusion. GSH fractional synthesis rate (FSR) was assessed from [(15)N]glutamate incorporation into blood and gut GSH, and duodenal protein synthesis from [(13)C]leucine incorporation into gut protein. Glutamine supplementation failed to alter erythrocyte GSH concentration (2189+/-86 vs. 1994+/-102 micromol L(-1) for glutamine vs. control; ns) or FSR (64+/-17% vs. 74+/-20% day(-1); ns). In the duodenum, glutamine supplementation was associated with a 92% rise in reduced/oxidized GSH ratio (P=.024) and with a 44% decline in GSH FSR (96+/-15% day(-1) vs. 170+/-18% day(-1); P=.005), whereas total GSH concentration remained unchanged (808+/-154 vs. 740+/-127 micromol kg(-1); P=.779). We conclude that, in dogs receiving enteral nutrition after a 3-day fast: (1) glutamine availability does not affect blood GSH, and, (2) in contrast, in the duodenum, the preserved GSH pool, along with a decreased synthesis rate, suggests that glutamine may maintain GSH pool and intestinal redox status by acutely decreasing GSH utilization.
Humbert
Bernard
B
INSERM U.539, Centre de Recherche en Nutrition Humaine, Nantes, 44093 Cedex 1, France.
Nguyen
Patrick
P
Martin
Lucile
L
Dumon
Henri
H
Vallette
Geneviève
G
Maugère
Pascale
P
Darmaun
Dominique
D
D000818:Animals; D004285:Dogs; D004386:Duodenum / Q000378:metabolism; D004750:Enteral Nutrition; D004912:Erythrocytes / Q000737:chemistry; D005260:Female; D018698:Glutamic Acid / Q000097:blood; D005973:Glutamine / Q000097:blood / Q000494:pharmacology*; D005978:Glutathione / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D007700:Kinetics; D008297:Male; D023421:Models, Animal; D010084:Oxidation-Reduction; D014176:Protein Biosynthesis
D005973:Glutamine; D018698:Glutamic Acid; D005978:Glutathione