Physiological doses of oral casein affect hepatic glycogen metabolism in normal food-deprived rats.
In a previous study, administration of casein hydrolysate to food-deprived rats at a dose of 4 g/kg body wt resulted in an increase in portal plasma glucagon concentration. This was associated with an activation of phosphorylase a and a decrease in hepatic glycogen concentration. The present study was undertaken to determine whether similar results would be obtained with smaller doses. Doses of 1 and 2 g/kg body wt were administered to food-deprived rats. At a dose of 2 g/kg, portal plasma glucagon concentration was significantly elevated. This was associated with a slight increase in phosphorylase a activity (P < 0.05) and a 50% decrease in hepatic glycogen concentration (P < 0.01). At a dose of 1 g casein hydrolysate/kg body wt, changes in portal plasma glucagon concentration, phosphorylase a activity and hepatic glycogen concentration generally were not observed. Hepatic glucose, uridine diphosphoglucose, ATP and glucose-6-phosphate concentrations were unaffected by either dose of casein hydrolysate. The data indicate a dose-response relationship between casein hydrolysate administration and effects on glycogen metabolism in the liver. Protein-induced glycogenolysis is likely to occur when rats ingest a moderate amount of a pure protein meal.
Gannon
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MC
Metabolic Research Laboratory, V.A. Medical Center, Minneapolis, MN, USA.
Nuttall
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FQ
D000255:Adenosine Triphosphate / Q000032:analysis; D000284:Administration, Oral; D000818:Animals; D002364:Caseins / Q000008:administration & dosage* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005508:Food Deprivation / Q000502:physiology*; D005934:Glucagon / Q000097:blood / Q000378:metabolism; D005947:Glucose / Q000032:analysis / Q000378:metabolism; D005952:Glucose-6-Phosphatase / Q000032:analysis; D006003:Glycogen / Q000032:analysis / Q000378:metabolism*; D006006:Glycogen Synthase / Q000032:analysis; D008099:Liver / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D010762:Phosphorylase a / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D002364:Caseins; D000255:Adenosine Triphosphate; D006003:Glycogen; D005934:Glucagon; D010762:Phosphorylase a; D006006:Glycogen Synthase; D005952:Glucose-6-Phosphatase; D005947:Glucose