GSBS Student Publications

Title

A hypersensitivity of glycogen phosphorylase activation in hearts of diabetic rats

Date

2-25-1981

Document Type

Article

Medical Subject Headings

Adenosine Triphosphate; Animals; Cyclic AMP; Diabetes Mellitus, Experimental; Enzyme Activation; Epinephrine; Glucosephosphates; Glycogen; Glycogen Synthase; Kinetics; Male; Myocardium; Phosphorylase Kinase; Phosphorylase Phosphatase; Phosphorylases; Protein Kinases; Rats

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

This study was initiated to determine whether glycogen phosphorylase activation was defective in hearts of alloxan diabetic rats. When hearts were perfused by gravity flow for 1 to 10 min with various concentrations of epinephrine, activation of glycogen phosphorylase in the diabetic was significantly greater at every time and epinephrine concentration than that seen in the normal. Cyclic AMP accumulation and protein kinase activation by epinephrine in the diabetic were not appreciably different or were lower than the normal responses to the hormone. The effects of epinephrine on cAMP and protein kinase were blocked in both normal and diabetic hearts by propranolol. While the beta blocker prevented phosphorylase activation in the normal hearts, it did not block phosphorylase activation by epinephrine in the diabetic hearts. Likewise, the alpha agonist phenylephrine activated phosphorylase in the diabetic but not in the normal hearts. While glucagon produced the same phosphorylase hypersensitivity in diabetic hearts, the cAMP and protein kinase responses were not altered by diabetes. Phosphorylase phosphatase activity was found to be unaltered by either epinephrine or diabetes, whereas phosphorylase kinase activation by epinephrine in the diabetic was double the normal response. These data are consistent with a diabetes-related unmasking of an alpha effect on cardiac phosphorylase activation and an unexplained increase in the sensitivity of phosphorylase kinase activation by protein kinase.

Rights and Permissions

Citation: J Biol Chem. 1981 Feb 25;256(4):1748-53.

Related Resources

Link to article in PubMed

Journal Title

The Journal of biological chemistry

PubMed ID

6257685