Vanadate

About: Vanadate is a research topic. Over the lifetime, 4497 publications have been published within this topic receiving 120109 citations. The topic is also known as: vanadate.

The insulin-like effect of vanadate on lipolysis in rat adipocytes is not accompanied by an insulin-like effect on tyrosine phosphorylation.

Abstract: Tyrosine phosphorylation of the insulin receptor and other intracellular proteins in rat adipocytes was examined using an immunoblot technique with antiphosphotyrosine antibody. Insulin at 10-7 M increased the tyrosine phosphorylation of the 95K subunit of the insulin receptor (15-fold) and proteins of 180K (7-fold) and 60K (23-fold). Increases in insulin-dependent phosphorylation of the three proteins were detectable at 1O-10 M insulin and attained steady state within 30 sec of insulin (10-7 M) addition. Small effects of insulin (<30% increases) were observed on proteins of 120K and 53K. In contrast to insulin, the effects of vanadate on tyrosine phosphorylation were small and nonspecific. Vanadate increased tyrosine phosphorylation of the 95K insulin receptor /3-subunit and the 120K and 60K proteins similarly, with increases of 1.5- to 3-fold at 1 mM and 2-fold or less at 200 and 50 μM. Vanadate-dependent tyrosine phosphorylation of the 180K protein increased to a maximum of only 30% at 200 μM. Tyrosine...

Multifunctional actions of vanadium compounds on insulin signaling pathways: Evidence for preferential enhancement of metabolic versus mitogenic effects

Abstract: The pathophysiologic importance of insulin resistance in diseases such as obesity and diabetes mellitus has led to great interest in defining the mechanism of insulin action as well as the means to overcome the biochemical defects responsible for the resistance. Vanadium compounds have been discovered to mimic many of the metabolic actions of insulin both in vitro and in vivo and improve glycemic control in human subjects with diabetes mellitus. Apart from its direct insulinmimetic actions, we found that vanadate modulates insulin metabolic effects by enhancing insulin sensitivity and prolonging insulin action. All of these actions appear to be related to protein tyrosine Phosphatase (PTP) inhibition. However, in contrast to its stimulatory effects, vanadate inhibits basal and insulin-stimulated system A amino acid uptake and cell proliferation. The mechanism of these actions also appears to be related to PTP inhibition, consistent with the multiple roles of PTPs in regulating signal transduction. While the precise biochemical pathway of vanadate action is not yet known, it is clearly different from that of insulin in that the insulin receptor and phosphatidylinositol 3′-kinase do not seem to be essential for vanadate stimulation of glucose uptake and metabolism. The ability of vanadium compounds to ‘bypass’ defects in insulin action in diseases characterized by insulin resistance and their apparent preferential metabolic versus mitogenic signaling profile make them attractive as potential pharmacological agents. (Mol Cell Biochem 182: 109-119, 1998)

Study of the mechanism of vanadate inhibition of the dynein cross-bridge cycle in sea urchin sperm flagella.

Abstract: The effect of vanadate on the ATP-induced disruption of trypsin-treated axonemes and the ATP-induced straightening of rigor wave preparations of sea urchin sperm was investigated. Addition of ATP to a suspension of trypsin-treated axonemes results in a rapid decrease in turbidity (optical density measured at 350 nm) concomitant with the disruption of the axonemes by sliding between microtubules to form tangles of connected doublet microtubules (Summers and Gibbons, 1971; Sale and Satir, 1977). For axonemes digested to approximately 93 percent of their initial turbidity, 5 {muM} vanadate completely inhibits the ATP-induced decrease in turbidity and the axonemes maintain their structural integrity. However, with axonemes digested to approximately 80 percent of their initial turbidity, vanadate fails to inhibit the ATP-induced decrease in turbidity and the ATP-induced structural disruption of axonemes, even when the vanadate concentration is raised as high as 100 mum. For such axonemes digested to 80 percent of their initial turbidity, the form of ATP-induced structural changes, in the presence of 25 muM vanadate, was observed by dark-field light microscopy and revealed that the axonemes become disrupted into curved, isolated doublet microtubules, small groups of doublet microtubules, and "banana peel" structures in which tubules have peeled back from the axoneme. Addition of 5 muM ATP to rigor wave sperm, which were prepared by abrupt removal of ATP from reactivated sperm, causes straightening of the rigor waves within 1 min, and addition of more than 10 muM ATP causes resumption of flagellar beating. Addition of 40 muM vanadate to the rigor wave sperm does not inhibit straightening of the rigor waves of 2 muM-1 mM ATP, although oscillatory beating is completely inhibited. These results suggest that vanadate inhibits the mechanochemical cycle of dyein at a step subsequent to the MgATP(2-)-induced release of the bridged dynein arms.

Sodium-dependent silicate transport in the apochlorotic marine diatom Nitzschia alba.

Abstract: Silicate uptake by Nitzschia alba cells is higher in medium containing Na+ than in media lacking Na+ but containing K+, Rb+, NH4+, Li+, or choline+. The initial rate is inhibited by monensin and gramicidin but not by valinomycin or nigericin and is less sensitive to inhibition by carbonyl cyanide m-chlorophenylhydrazone (CCCP). In isolated membrane vesicles, silicate is taken up when a Na+ gradient is imposed across the membrane or is generated by cytoplasmic Na+,K+-ATPase. H+ or K+ gradients in either direction do not stimulate uptake. Na+-gradient-dependent uptake is inhibited by monensin but not by CCCP, valinomycin, or vanadate, which inhibits the cytoplasmic Na+,K+-ATPase. Uptake increases if an internally negative potential is imposed across the membrane. The vesicular uptake shows saturation kinetics with a Km of 62 μM and a Vmax of 4.1 nmol/mg of protein per min. In intact cells, the initial rate of silicate uptake increases with pH up to 9.5. Thus, in N. alba, silicate is symported with Na+, and the transport system is driven by the Na+ gradient that is generated and maintained across the membrane by the activity of Na+,K+-ATPase.