title: Pervanadate [peroxide(s) of vanadate] mimics insulin action in rat adipocytes via activation of the insulin receptor tyrosine kinase.
abstract: Both vanadate and hydrogen peroxide (H2O2) are known to have insulin-mimetic effects. We previously reported that the mixture of vanadate plus H2O2 results in the generation of a peroxide(s) of vanadate, which strongly enhances IGF-II binding to rat adipocytes (Kadota et al., 1987b). We now report that pervanadate mimics insulin in isolated rat adipocytes to (1) stimulate lipogenesis, (2) inhibit epinephrine-stimulated lipolysis, and (3) stimulate protein synthesis. The efficacy of pervanadate is comparable to that of insulin. However, it is 10(2)-10(3) times more potent than vanadate alone. Exposure of intact rat adipocytes to pervanadate was found to activate the WGA-purified insulin receptor tyrosine kinase assayed with the exogenous substrate poly(Glu80/Tyr20) in a dose-dependent manner to a maximum of 1464% of control at 10(-3) M compared with a maximum insulin effect of 1046% at 10(-6) M. In contrast, in vitro assayed autophosphorylation of the WGA-purified extract was increased 3-fold after exposure of intact cells to insulin but not significantly increased after pervanadate. Furthermore, high concentrations of pervanadate (10(-5) M) inhibited subsequent in vitro added insulin-stimulated autophosphorylation. In vitro addition of pervanadate to WGA-purified receptors could not stimulate autophosphorylation or exogenous tyrosine kinase activity and did not inhibit insulin-stimulated autophosphorylation. Labeling of intact adipocytes with [32P]orthophosphate followed by exposure to 10(-4) M pervanadate increased insulin receptor beta-subunit phosphorylation (7.9 +/- 3.0)-fold, while 10(-7) M insulin and 10(-4) vanadate increased labeling (5.3 +/- 1.8)- and (1.1 +/- 0.2)-fold, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Protein and Polypeptide Hormone Laboratory, Royal Victoria Hospital, Montreal, Quebec, Canada.
authors.forename: I G
authors.initials: IG
authors.lastname: Fantus
authors.forename: S
authors.initials: S
authors.lastname: Kadota
authors.forename: G
authors.initials: G
authors.lastname: Deragon
authors.forename: B
authors.initials: B
authors.lastname: Foster
authors.forename: B I
authors.initials: BI
authors.lastname: Posner
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D007328:Insulin / Q000502:physiology; D007700:Kinetics; D050356:Lipid Metabolism; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D010545:Peroxides / Q000494:pharmacology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology*
chemical_list: D007328:Insulin; D010545:Peroxides; D014638:Vanadates; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin