Effect of vanadate on rat myometrium plasma membrane enzyme activities.
Vanadate inhibited K+-activated and K+-activated ouabain-sensitive p-nitrophenyl phosphatases of rat myometrium at nanomolar concentrations. The vanadate concentrations required for 50% inhibition were 220 +/- 30 nM for the K+-activated component of the enzyme and 200 +/- 30 nM for the K+-activated ouabain-sensitive component. Micromolar concentrations of vanadate inhibited acid and alkaline p-nitrophenyl phosphatases. ATP-dependent Ca uptake by the plasma membrane vesicles was not inhibited by 10nM - 1 mM vanadate. Mg2+-ATPase was also not affected. Thus K+-activated and K+-activated ouabain-sensitive p-nitrophenyl phosphatase activities of the plasma membrane were most sensitive to inhibition by vanadate. Preliminary experiments demonstrated that similar to ouabain, vanadate inhibited potassium-induced abolition of spontaneous contractile activity of isolated rat myometrium in K-free Krebs. This effect of vanadate is consistent with vanadate inhibition of K+-activated ouabain-sensitive p-nitrophenyl phosphatase.
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009215:Myometrium / Q000201:enzymology* / Q000648:ultrastructure; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000201:enzymology*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
D014639:Vanadium; D014638:Vanadates; D010042:Ouabain