Insulin receptor kinase activity in rat liver. Regulation by fasting and high carbohydrate feeding.

摘要: Insulin receptor kinase activity was measured in partially purified preparations from livers of rats fed a standard diet or subjected to either prolonged fasting high carbohydrate (CHO) diet, conditions known decrease (fasting) and increase insulin action. Basal insulin-stimulated phosphorylation the beta subunit comparable all groups with half-maximal effect at approximately 2.0 ng/ml free 10-12-fold maximal effect. The receptors three further examined using synthetic polypeptide Glu 4:Tyr 1. rates 1 were highest CHO-fed lowest fasted group. magnitude these differences same absence presence insulin; thus, alterations CHO feeding entirely expressed basal rate peptide phosphorylation. Antireceptor antibody immunoprecipitated 70-80% each group; remaining 20-30% showed minor group when normalized for amount protein present preparations. These results indicate that intrinsic receptor. increased Vmax by 30 fmol phosphorus/fmol binding activity/30 min groups; however, absolute Km unaffected (approximately 0.25 mg/ml) groups. findings produce changes which are regulated mechanisms independent show substrate specificity so detected one (Glu 1) but not another (the subunit).