title: Glycogen synthase and phosphorylase activities during glycogen repletion in endotoxemic rats.
abstract: The activities of glycogen synthase and glycogen phosphorylase were quantitated in liver and skeletal muscle removed following glucose infusion in hemodynamically stable endotoxin-treated rats. Four hours after the IV injection of endotoxin or saline, rats were infused with 235 mumole/min/kg of glucose or saline for up to 4 additional hr. Saline-infused endotoxemic rats had lower basal glycogen content in muscle and liver, which was associated with an increased phosphorylase a activity in both tissues compared to controls. During the glucose infusion, the rate of glycogen repletion in muscle was similar in the two groups. Skeletal muscle phosphorylase a and glycogen synthase I & D activities were elevated above control values in endotoxemia, while glycogen synthase I activity remain unchanged. These changes in the activity of muscle phosphorylase and synthase are consistent with an increased flux of carbon into and out of glycogen and a normal rate of net glycogen synthesis during glucose infusion in endotoxin-treated rats. In contrast to muscle, hepatic glycogen synthesis by endotoxemic animals was reduced compared to glucose-infused controls. Hepatic glycogen repletion in control animals appeared to be mediated primarily by a glucose-induced suppression of phosphorylase a activity rather than an increased glycogen synthase activity. Glucose infusion failed to decrease phosphorylase a activity in endotoxin-treated rats, which may be causally related to the impaired ability of these animals to replete liver glycogen.
mesh_terms: D000818:Animals; D004731:Endotoxins / Q000633:toxicity; D005636:Fructosephosphates / Q000032:analysis; D005947:Glucose / Q000494:pharmacology; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000032:analysis; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000032:analysis*; D007328:Insulin / Q000097:blood; D008099:Liver / Q000201:enzymology; D008297:Male; D009132:Muscles / Q000201:enzymology; D006005:Phosphorylases / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D014115:Toxemia / Q000378:metabolism*
chemical_list: D004731:Endotoxins; D005636:Fructosephosphates; D005958:Glucosephosphates; D007328:Insulin; D019298:Glucose-6-Phosphate; C027618:fructose-6-phosphate; D006003:Glycogen; D006005:Phosphorylases; D006006:Glycogen Synthase; D005947:Glucose