Vanadate potentiates the glycogenic action of insulin-like growth factors on isolated diaphragm.
Na3VO4 (6.5 mumol/100 g rat weight), co-injected with a trace amount of [14C]glucose, increased within 15 min the incorporation of radiolabel in diaphragmal glycogen. After 2 h the vanadate-induced increases were 12-fold in the diaphragm and 7-8-fold in heart and liver. In contrast, when added to isolated diaphragms for up to 1 h, vanadate (0.1-5 mM) had no effect on the synthesis of glycogen from 5 mM glucose. In search of a putative mediator of vanadate's action in vivo, insulin and the insulin-like growth factors (IGFs) were considered. Their plasma concentration was not affected by vanadate treatment. In isolated diaphragms, 1 mM vanadate did not potentiate insulin-induced glycogen synthesis, but it caused a several-fold increase in glycogen synthesis in the presence of concentrations of IGF-I which, alone, had no effect. A similar synergism occurred between vanadate and IGF-II. We propose that the glycogenic action of vanadate in vivo, at least in some tissues, involves a potentiation of the action of IGF-I.
Vandorpe
G
G
Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Belgium.
Bollen
M
M
Van Herck
E
E
Bouillon
R
R
Stalmans
W
W
D000818:Animals; D001786:Blood Glucose; D003964:Diaphragm / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D006003:Glycogen / Q000096:biosynthesis*; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000097:blood / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014638:Vanadates / Q000494:pharmacology*
D001786:Blood Glucose; D007328:Insulin; D014638:Vanadates; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D006003:Glycogen