Acute effects of insulin and glucagon on hepatic casein kinase 2 in adult fed rats: correlation of the effects on casein kinase 2 with the changes in glycogen synthase activity.
Administration of insulin to adult fed rats caused an inactivation of hepatic casein kinase 2 as determined by the decrease in the activity ratio measured at a low (0.1 mg/ml) and a high (1.0 mg/ml) concentration of beta-casein. Maximal inactivation occurred 45 min after injection and the dose for half-maximal effect was 44 micrograms/kg. The effect of insulin was due to an increase in the apparent Km value for the protein substrate but the magnitude of the effect depended on the substrate used, decreasing in the order beta-casein greater than glycogen synthase much greater than whole casein. The activation of casein kinase 2 by glucagon (M. Pérez, J. Grande, and E. Itarte (1988) FEBS Lett. 238, 273-276) was also more marked with beta-casein and glycogen synthase than with whole casein. A good correlation was observed between the time- and dose-dependent activation of glycogen synthase and inactivation of casein kinase 2 promoted by insulin. Similarly, the inactivation of glycogen synthase by glucagon correlated with the activation of casein kinase 2 caused by this hormone. The possible involvement of casein kinase 2 on the mechanism(s) through which these hormones control hepatic glycogen synthase is discussed.
Grande
J
J
Departament de Bioquímica i Biología Molecular, Facultat de Ciencies, Universitat Autonoma de Barcelona, Spain.
Pérez
M
M
Plana
M
M
Itarte
E
E
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D047388:Casein Kinases; D004435:Eating; D005934:Glucagon / Q000494:pharmacology*; D006006:Glycogen Synthase / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D005934:Glucagon; D006006:Glycogen Synthase; D011494:Protein Kinases; D047388:Casein Kinases