Glycogenolytic, noninsulin-like effects of vanadate on rat hepatocyte glycogen synthase and phosphorylase

Vanadate inactivated rat hepatocyte glycogen synthase and activated glycogen phosphorylase in a dose- and time-dependent manner. These effects were observed in hepatocytes from both fasted as well as fed rats. When rat hepatocytes were preincubated with [32P]phosphate and then with vanadate, and the...

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Bibliographic Details
Published in:The Journal of biological chemistry 1987-01, Vol.262 (1), p.218-222
Main Authors: Bosch, F, Ariño, J, Gómez-Foix, A M, Guinovart, J J
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Calcium - physiology
Cell physiology
Cyanogen Bromide
Enzyme Activation - drug effects
Fasting
Food
Fundamental and applied biological sciences. Psychology
Glycogen - metabolism
Glycogen Synthase - antagonists & inhibitors
Glycogen Synthase - metabolism
Insulin - pharmacology
Liver - enzymology
Male
Miscellaneous
Molecular and cellular biology
Phosphates - metabolism
Phosphorylases - metabolism
Phosphorylation
Rats
Rats, Inbred Strains
Vanadates
Vanadium - pharmacology
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Summary:Vanadate inactivated rat hepatocyte glycogen synthase and activated glycogen phosphorylase in a dose- and time-dependent manner. These effects were observed in hepatocytes from both fasted as well as fed rats. When rat hepatocytes were preincubated with [32P]phosphate and then with vanadate, and the 32P-labeled glycogen synthase was specifically immunoprecipitated, it was observed that vanadate stimulated the phosphorylation of the 88,000-dalton subunit of glycogen synthase. All of the phosphate was located in the same two CNBr fragments of the enzyme which are phosphorylated by glucagon and other glycogenolytic hormones. In cells incubated in a calcium-depleted medium, vanadate was still able to inactivate glycogen synthase but its effects on phosphorylase were essentially lost. These results demonstrate that, in the hepatocyte, vanadate exerts opposite effects than in the adipocyte and skeletal muscle, where vanadate has an insulin-like action.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(19)75913-4