PMID: 2498142Jun 1, 1989Paper

Control of glycogen synthase and phosphorylase in hepatocytes from diabetic rats. Effects of glucagon, vasopressin, and vanadate

Diabetes
J E Rodríguez-GilF Bosch

Abstract

Although glycogen synthase is present in a highly inactivated state in hepatocytes from streptozocin-induced diabetic rats, glucagon, vasopressin, and vanadate are still able to further decrease the basal activity of the enzyme. This inactivation was observed with the low-to-high glucose 6-phosphate activity ratio assay. The inactivation of glycogen synthase occurred concomitantly with the activation of glycogen phosphorylase. When hepatocytes from diabetic rats were incubated with [32P]phosphate and then with the agents and when the 32P-labeled glycogen synthase was immunoprecipitated, we observed that the 32P bound to the 88,000-Mr subunit increased in all cases. All the [32P]phosphate was located in two cyanogen bromide fragments of the enzyme, indicating that the enzyme was phosphorylated at multiple sites. The fragments were precisely those phosphorylated by glycogenolytic hormones in hepatocytes from normal rats. These results demonstrated that hepatic glycogen synthase, although highly inactive, is under potential hormonal control in diabetes and that the enzyme has not reached its maximal level of phosphorylation. Furthermore, they indicated that vanadate behaves as a glycogenolytic agent regarding its effects on glycog...Continue Reading

Citations

Dec 6, 1995·Molecular and Cellular Biochemistry·S K PandeyA K Srivastava
Aug 1, 1995·Molecular and Cellular Biochemistry·S Pugazhenthi, R L Khandelwal
Jul 9, 1996·Proceedings of the National Academy of Sciences of the United States of America·T FerreA Valera
Dec 1, 1994·European Journal of Biochemistry·J M Fernández-NovellJ J Guinovart

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