Glucose stimulation of heart phosphorylase phosphatase activity in vitro and in vivo.
To determine the mechanism of the glucose stimulation, glucose or glucose-6-phosphate was added to dilute heart extracts in the presence or absence of AMP. The intracellular glucose, tissue glucose-6-phosphate, and tissue AMP concentrations were also determined in 24-h starved animals given glucose; 24-h starved animals given insulin as well as diabetic starved and diabetic starved insulin-treated animals were also studied. The A0.5 for glucose stimulation of cardiac phosphorylase phosphatase activity was approximately 1.2 mM. The A0.5 for glucose-6-phosphate was approximately 0.02 mM. The glucose-6-phosphate concentration in all animals exceeded the A0.5 by 10-fold. However, the intracellular glucose concentration in the glucose-treated, insulin-treated, diabetic, and diabetic insulin-treated rats was in the range of the A0.5 for stimulation of phosphorylase phosphatase activity. AMP completely inhibited phosphorylase phosphatase activity at a concentration of 0.2 mM. Physiological concentrations of glucose and glucose-6-phosphate partially reversed this inhibition. Administration of glucose or insulin resulted in an increase in intracellular glucose concentration, an increase in tissue glucose-6-phosphate and a decrease in tissue AMP concentrations. These data suggest that glucose may be a physiological regulator of phosphorylase phosphatase in heart muscle as it is in liver.
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010765:Phosphorylase Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D013217:Starvation
D005958:Glucosephosphates; D007328:Insulin; D000249:Adenosine Monophosphate; D019298:Glucose-6-Phosphate; D010749:Phosphoprotein Phosphatases; D010765:Phosphorylase Phosphatase; D005947:Glucose