Vanadate inhibitory effect

Vanadium compounds have an inhibitory effect against induced rat hepatocar-cinogenesis by limiting cell proliferation and chromosomal aberrations in the pre-neoplastic stages of the development of this cancer [169], These antineoplastic effects of vanadium could be related to the induction of apoptosis and selective DNA damage in tumor cells [170], Vanadate has also proven effective against induction of colon carcinomas [171]. A vanadium(III) cysteine compound has been shown to... 

By using radioisotopes, the influx of vanadate into the blood cells of A. nigra has been studied85. The influx of phosphate, sulfate and dichromate, and the inhibitory effect of these oxoanions on vanadate influx have also been determined. The rate of vanadate influx was measured in the presence of metabolic inhibitors and inhibitors of anion transport. In this study, EPR spectroscopy was used to follow changes in the concentration of reduced vanadium within tunicate blood cells exposed to vanadate. 

In investigations of the effects of various compounds on the activity of an enzyme, vanadate was clandestinely added to inhibit this enzyme (LPP-i) while the experiments purported to show the inhibitory effects of natural lipid effectors the researcher not only falsified his own data but deliberately added vanadate to experiments conducted by colleagues ... 

Since disturbed acid phosphatase activity has been associated with pathological conditions, the research has focused on the development of diagnostic methods for detection of activity as a marker for the onset of the disease, and in some extent to the development of inhibitors rather than activators to treat those conditions in which the increase in enzyme activity has a direct effect on the evolution of the disease. In particular, only the development of bisphospho-nate derivatives as inhibitors for tartrate-resistant acid phosphatase found their way to the market for treatment of osteoporosis [41], Typical inhibition of phosphatase activity includes anionic species such as L-(+)-tartrate, phosphate, vanadate, molybdate, and fluoride and neutral molecules such as formaldehyde. Vanadate ion,, is a competitive unspecific inhibitor for acid phosphatases by forming transition state analogs. Other oxoanions such as molybdate and tungstate also show inhibitory effects on... 

Tyrosine kinases have been implicated in Ca +-sensitization largely as the result of the inhibitory effects of tyrosine kinase inhibitors, genistein and vanadate, and the correlation between tyrosine phosphorylation and vanadate- or agonist-induced contractions (Di Salvo et al. 1993a,b, 1994, 1997 Steusloff et al. 1995). However, the tyrosine-phosphorylated proteins have yet to be directly linked to a known contractile regulatory mechanism i.e., MLCK, SMPP-IM) and evaluation of the relationships between tyrosine phosphorylation and modulation of Ca +-sensitization of contraction in intact muscle is somewhat complicated by concurrent changes in cytosolic Ca (Di Salvo et al. 1994,1997), possibly as the result of activation of PLC-y (Marrero et al. 1994) or Gaq.n (Umemori et al. 1997). 

The current preferred postulated mechanism of vanadium s in vitro effects is that vanadate stimulates specific protein-tyrosine phosphorylation by virtue of its inhibitory actions on appropriate PTPases. Routine addition of vanadate to cell lysates, particularly for tyrosine kinase assays, is testimony of the ability of vanadate to preserve the phosphotyrosine content of cells. The preponderance of evidence favors a post-receptor mechanism in stimulating glucose utilization, perhaps also involving a cytosolic i.e. non-receptor) protein tyrosine kinase that is stimulated preferentially by vanadium and may be insulin independent. Vanadyl is not a potent PTPase inhibitor. " Thus, whatever portion of intracellular vanadium is present as vanadyl is probably acting by some alternative mechanism. ... 

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