Endocytic vesicles are acidified by an electrogenic proton pump and a parallel chloride conductance; however, acidification might be decreased if electrogenic transporters, such as Na,K-ATPase, that increase vesicle interior-positive membrane potential were also present. We examined this issue in early rat liver endosomes using ion substitution and inhibitors to alter Na,K-ATPase activity. Thes...

Vanadate, an inhibitor of tyrosine phosphatases, has insulin-mimetic properties. It has been shown that acute vanadate administration enhances glucose uptake independently of phosphatidylinositol (PI) 3-kinase and p38 MAPK. However, therapeutic vanadate use requires chronic administration, and this could potentially involve a different signaling pathway(s). Thus, we examined the mechanisms by w...

When present at intracellular concentrations above micromolar, vanadate becomes toxic to most organisms. However, the yeast Hansenula polymorpha is able to grow on vanadate concentrations in the millimolar range, showing at the same time modifications in cellular ultrastructure and polyphosphate metabolism. Here, the development of the ultrastructural changes, and of vacuolar and secretory acti...

Orthovanadate (vanadate) inhibited the platelet aggregation induced by platelet-activating factor (PAF) in a dose-dependent manner. Propranolol, a nonspecific beta-adrenergic receptor antagonist, and H-8, a selective inhibitor of cAMP-dependent protein kinase (PKA), suppressed the inhibition of the PAF-induced platelet aggregation by vanadate. Vanadate increased the cAMP content in platelets ac...

It was found that wild type yeast Pichia pastoris can tolerate vanadate concentration as high as 25 mM in the growth medium. Moreover, four vanadate-resistant P. pastoris strains designated JC100/1, JC100/3, JC100/9 and JC100/15 exhibiting tolerance up to 150 mM vanadate were selected. Growth of P. pastoris was correlated with vanadate to vanadyl reduction and its accumulation in the growth med...

The interaction of vanadate ions with the Ca-ATPase from sarcoplasmic reticulum vesicles was studied in a native and a fluorescein-labeled ATPase preparation (Pick, U., and Karlish, S. J. D. (1980) Biochim. Biophys. Acta 626, 255-261). Vanadate induced a fluorescence enhancement in a fluorescein-labeled enzyme, indicating that it shifts the equilibrium between the two conformational states of t...

The possible involvement of a 15-kDa phosphotyrosyl protein, pp15, in insulin action was investigated by using the insulin-mimetic agent, vanadate. Vanadate, a phosphotyrosine phosphatase inhibitor, was found to mimic insulin in 3T3-L1 adipocytes by three criteria. First, kinetic and concentration-dependence studies verified the insulin-like effect of vanadate in activating 2-deoxyglucose uptak...

Direct measurements of the stiffness (elastic bending resistance) of demembranated sera urchin sperm flagella were made in the presence of MgATP2- and vanadate. Under these conditions, the flagellum is in a relaxed state, with a stiffness of approximately 0.9 x 10(-21) N m2, which is approximately 5% of the stiffness obtained in the rigor state in the absence of MgATP2-. MgADP- dose not substit...