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

Bosch, Fátima; Ariño, Joaquı́n; Gómèz-Foix, Anna M.; Guinovart, J.J.

doi:10.1016/s0021-9258(19)75913-4

Cited by 46 publications

(4 citation statements)

References 28 publications

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“…Although more total phosphate was incorporated in CB-2, on a percentage basis the increase in the [32P]Pi content of CB-1 was more pronounced. This is similar to the pattern of phosphorylation observed after treatment of hepatocytes with glycogenolytic agents such as vasopressin, adrenaline and vanadate [1,2,14]. These data prove the covalent nature of the modification of glycogen synthase by prostaglandins.…”

Section: P-cnbr Fragmentssupporting

confidence: 82%

“…Stock solutions of prostaglandins were made in dimethyl sulphoxide. At the end of the incubation, cells were centrifuged and cell pellets homogenized as described previously [14]. Isolation of 32P-labelled glycogen synthase Glycogen synthase was isotopically labelled by preincubation of hepatocytes for 45 min with [32P]P1 (0.1 mCi/ml) in a low-phosphate (0.1 mM) version of the above Krebs bicarbonate buffer (pH 7.4).…”

Section: Methodsmentioning

confidence: 99%

“…For CNBr cleavage, immunopellets were treated as described in ref. [14]. The analysis of glycogen synthase subunit or CNBr phosphopeptides was carried out by electrophoresis in polyacrylamide gels in the presence of SDS, with 7 %acrylamide or 6-20 %-gradient-acrylamide slab gels as described in ref.…”

Section: Methodsmentioning

confidence: 99%

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Prostaglandins E2 and F2α affect glycogen synthase and phosphorylase in isolated hepatocytes

Gómèz-Foix

Rodríguez‐Gil

Guinovart

et al. 1989

Biochemical Journal

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Prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) inactivated glycogen synthase and activated glycogen phosphorylase in rat hepatocytes in a dose- and time-dependent manner. These effects were dependent on the presence of Ca2+ in the incubation medium. When glycogen synthase was immunoprecipitated from cells incubated with [32P]Pi and then treated with PGE2 or PGF2 alpha, there was increased phosphorylation of the 88 kDa subunit of the enzyme. This phosphorylation affected two CNBr fragments of the glycogen synthase, CB-1 and CB-2, the same fragments that are phosphorylated by different glycogenolytic hormones. No phosphorylation of glycogen synthase by prostaglandins was observed in the absence of Ca2+. Thus the effect of PGE2 and PGF2 alpha on these glycogen-metabolizing enzymes supports a role for regulation by prostaglandins of glucose metabolism in parenchymal liver cells.

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Section: P-cnbr Fragmentssupporting

confidence: 82%

Section: Methodsmentioning

confidence: 99%

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Prostaglandins E2 and F2α affect glycogen synthase and phosphorylase in isolated hepatocytes

Gómèz-Foix

Rodríguez‐Gil

Guinovart

et al. 1989

Biochemical Journal

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“…This promotion of glucose uptake (and associated inhibition of lipolysis) in a tissue-specific manner can be duplicated by vanadium compounds . Insulin also serves to counteract catabolic hormones, such as glucagon, and to suppress production of glucose in the liver, effects which are not always replicated by vanadium . Vanadium compounds can never completely substitute for insulin; however, many of the observed in vitro and in vivo effects are insulin-like. , We use the term insulin mimic in this more general sense throughout our review.…”

Section: Insulin In Glucose and Fat Metabolismmentioning

confidence: 99%

Vanadium Compounds as Insulin Mimics

1999

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Vanadate inhibits glucose output from isolated perfused rat liver

et al. 1991

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Previous studies have demonstrated that vanadate ions mimic many of the actions of insulin in in vitro systems. Also, vanadate administered to diabetic hyperglycemic rats lowers their blood glucose levels to normal values. In this study we demonstrate that vanadate inhibits glucose output in the isolated perfused rat liver. Glucose production was suppressed maximally (about 50% to 60%), on addition of extremely low vanadate ion concentrations (0.5 to 1 mumol/L). This concentration is about two log units lower than the vanadate ion concentrations that are required to activate hexose uptake and glucose metabolism in vitro and is within the range of endogenous intracellular vanadium concentration. Insulin had little or no effect in inhibiting hepatic glucose output in this experimental system. The effect of vanadate ions is rapid in onset and is not accompanied by any signs of liver toxicity as assessed by various criteria. In conclusion, the study indicates that (a) vanadate ions inhibits hepatic glucose output, maximally and at extremely low, nontoxic concentrations (ID50 = 0.7 +/- 0.1 mumol/L). (b) The modulation action of the ion is fast and probably occurs at point(s) distal to the insulin receptor itself. (c) The liver participates in the process of maintaining euglycemia in diabetic rats receiving optimal doses of vanadate orally.

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

Cited by 46 publications

References 28 publications

Prostaglandins E2 and F2α affect glycogen synthase and phosphorylase in isolated hepatocytes

Prostaglandins E2 and F2α affect glycogen synthase and phosphorylase in isolated hepatocytes

Vanadium Compounds as Insulin Mimics

Vanadate inhibits glucose output from isolated perfused rat liver

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