Glutamine is a good substrate for glycogen synthesis in isolated hepatocytes from 72 h-starved rats, but not from 24 h- or 48 h-starved rats.
In isolated hepatocytes from 24 h-starved rats, no glycogen synthesis was observed in the presence of glutamine. By contrast, glutamine was the best gluconeogenic substrate to induce glycogen synthesis in isolated hepatocytes from 72 h-starved rats. The effect of glutamine on glycogen synthesis was not accompanied by parallel changes in glucose or lactate production. Glutamine activated glycogen synthase independently of the starvation period; however, the extent of synthase activation was 2-fold higher in isolated hepatocytes from 72 h-starved rats than in hepatocytes from 24 h-starved rats. This increase in synthase activation was associated with increased cell swelling. The rate of glutamine transport was not significantly different in hepatocytes from 24 h- and 72 h-starved rats. By contrast, the intracellular glutamate concentration was 1.5-fold higher after 3 days of starvation in hepatocytes incubated with 5 mM-glutamine. We propose that glutamine may play a key role in the glycogen synthesis observed in vivo after 3 days of starvation.
Mouterde
O
O
Groupe de Biochimie et Physiopathologie Digestive et Nutritionnellle, U.F.R. Médecine-Pharmacie, Saint-Etienne du Rouvray, France.
Claeyssens
S
S
Chedeville
A
A
Lavoinne
A
A
D000818:Animals; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D005943:Gluconeogenesis / Q000502:physiology; D005947:Glucose / Q000096:biosynthesis / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism* / Q000494:pharmacology; D007773:Lactates / Q000096:biosynthesis; D019344:Lactic Acid; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008112:Liver Glycogen / Q000096:biosynthesis*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013217:Starvation / Q000378:metabolism*; D013268:Stimulation, Chemical; D013379:Substrate Specificity; D013997:Time Factors
D002250:Carbon Radioisotopes; D007773:Lactates; D008112:Liver Glycogen; D005973:Glutamine; D019344:Lactic Acid; D005947:Glucose