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PubMed1990

Tetravalent vanadium mediated oxidation of low density lipoprotein.

1. Tetravalent vanadium causes oxidation of low density lipoprotein (LDL) as manifest by protein degradation and lipid peroxidation. 2. Oxidative modification of the apolipoprotein B-100 is paralleled by the formation of thiobarbituric acid reactive substance and fluorescent chromolipid production. 3. The metal chelators ethylenediamine tetracetic acid and desferrioxamine, and the alcohols, ethanol and isopropanol inhibit the oxidation of LDL by tetravalent vanadium. No inhibition is observed with superoxide dismutase, catalase or mannitol. 4. The data suggest that aldehydes formed during the process of lipid peroxidation induced by tetravalent vanadium react with the proteins in LDL to form fluorescent chromolipids and that the oxidative process originates within the hydrophobic domain of LDL.

1-Propanol↗
PubMed1989

Sustained prevention of myocardial and metabolic abnormalities in diabetic rats following withdrawal from oral vanadyl treatment.

Earlier studies revealed a general amelioration of diabetes-induced alterations in the rat following chronic oral vanadyl treatment. Recently, some streptozotocin-diabetic animals treated similarly were observed to remain euglycemic after withdrawal from vanadyl. In the present study, the diabetic profile of these animals (STZ-T) was investigated. After 3 weeks of treatment with vanadyl followed by 13 weeks of withdrawal, plasma concentrations of glucose, insulin, lipids, and thyroid hormones in the STZ-T animals were returned to control levels. Myocardial dysfunction and increased glycerol output from adipose tissue in untreated-diabetic (STZ) rats were also found to be normalized in the STZ-T group. Furthermore, there was no evidence of cataracts in these animals compared with age-matched STZ rats. These findings indicate that short-term oral treatment of diabetic rats with vanadyl induces beneficial changes that persist following withdrawal of the treatment. The results of these studies may suggest a possible new treatment protocol that could be incorporated into the management of diabetes.

Adipose Tissue↗
PubMed1984

The effects of vanadate on 45Ca exchange and enzyme secretion in the rat exocrine pancreas.

The effects of vanadate on calcium homeostasis and enzyme secretion have been assessed in the incubated pancreas of young rats. Vanadate causes an acceleration of 45Ca efflux from pre-loaded uncinate glands; amylase release is reversibly increased for the duration of exposure to vanadate. Alkaline orthovanadate is most effective in eliciting these responses; its effects are greatly reduced at pH 7.4. However, changes in pH alone do not mimic these effects. Other vanadium oxides (meta-vanadate, vanadium pentoxide and vanadyl sulphate) are poor secretagogues. Alkaline ortho-, or meta-vanadate also causes an increased calcium uptake although this does not seem to be responsible for the observed secretory response. Vanadate is thought to stimulate pancreatic secretion by an effect on intracellular calcium store(s).

Amylases↗
PubMed1990

Chromosomal aberrations, sister-chromatid exchanges, cell-cycle kinetics and satellite associations in human lymphocyte cultures exposed to vanadium pentoxide.

Treatment of human lymphocytes with vanadium pentoxide (V2O5) was not found to increase the frequency of structural chromosomal aberrations (CA) and sister-chromatid exchanges (SCE). However, V2O5 significantly increased polyploid cell frequency; also, the mitotic index (MI) was significantly decreased, and the average generation time (AGT) was significantly increased. Finally, the frequency of cells with satellite associations (SA), the frequency of SA per cell, and the frequency of chromosomes associated increased in treated cultures.

Adult↗
PubMed1991

Reactivation of vanadium bromoperoxidase; inhibition by metallofluoric compounds.

The effect of phosphate analogs (pyrophosphate, aluminofluoride and beryllofluoride complexes) on the reactivation of apobromoperoxidase by vanadate was studied. P2O7(4-) inhibited the reactivation in the millimolar range. Of the different aluminofluoride complexes, only AlF4- was inhibitory. In addition, BeF4(2-) also appeared to bind with high affinity to the apobromoperoxidase, thus inhibiting the reactivation very strongly. The inhibition observed supports a mechanism in which the fluorometallic complexes act as analogs of vanadate and bind accordingly to the apobromoperoxidase.

Aluminum↗
PubMed1991

Evaluation of the efficacy of various chelating agents on urinary excretion and tissue distribution of vanadium in rats.

The effect of repeated intraperitoneal administration of Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid), ascorbic acid, deferoxamine (DFOA) or 2-mercaptosuccinic acid on urinary excretion and tissue distribution of vanadium was assessed in rats which had previously received 12 intraperitoneal injections of sodium metavanadate (1.84 mg/kg per injection) or vanadyl sulphate trihydrate (6.35 mg/kg per injection) during a 4-week period. Chelating agents were administered daily for 5 days at doses equal to one-eighth of their respective LDSO. Only Tiron significantly decreased the tissue concentration of vanadium, whereas DFOA and Tiron significantly enhanced the urinary excretion of vanadium after repeated parenteral administration of sodium metavanadate. Again, only Tiron significantly increased the urinary elimination of vanadium following vanadyl sulphate administration. The results of this study show that Tiron has potential beneficial effects in the treatment of repeated intraperitoneal vanadium poisoning, while the effectiveness of DFOA is very uncertain. 2-Mercaptosuccinic and ascorbic acids were not effective as antidotes for parenteral vanadium intoxication.

Animals↗
PubMed1994

Determination of 51V quadrupole and chemical shift tensor orientations in V2O5 by analysis of magic-angle spinning nuclear magnetic resonance spectra.

Magic-angle spinning (MAS) 51V nuclear magnetic resonance (NMR) spectra of V2O5 have been recorded at various fields to evidence the relative effects of the quadrupole interaction and electronic shielding at the nucleus. A refinement of the spectra using theoretical simulations has been performed assuming a simultaneous existence of these two anisotropic interactions. The relative orientation of the principal axes for both tensors has been obtained. The results agree with previous single-crystal studies. Reliability of the results is discussed. A fundamental indetermination of the actual relative tensor orientations remains, owing to the powder nature of the sample.

Anisotropy↗
PubMed1995

Fractional power time dependence of the nuclear magnetization in the presence of paramagnetic impurities.

We extend the theory of growth of the nuclear magnetization in the presence of paramagnetic impurities and the absence of spin diffusion to the case of multi-paramagnetic centers. We show that for short times after saturation pulses, the rate of growth of the magnetization is proportional to t alpha where t is the time and alpha = 1/3, 1/2 and 2/3 for one-, two- and three-dimensional systems, respectively. We also present experimental data for which the total time-dependent magnetization is proportional to exp[-(t/T1) alpha], which reduces to the above time dependence for short times.

Electron Spin Resonance Spectroscopy↗
PubMed1996

Study by 31P NMR spin echo mapping of vanadium phosphorus oxide catalysts.

Vanadium phosphorus oxides (VPO) containing vanadium ions in the +3 and +4 oxidation states, namely VPO4, (VO)2P2O7, VOHPO4.0.5H2O and VO(H2PO4)2 have been characterized using 31P solid state NMR spectroscopy. Because of couplings between the unpaired electrons of V4+ or V3+ ions and 31P nuclei, 31P NMR lines are drastically broadened and shifted by more than 4500 ppm in the case of the V3+ phases. It is therefore necessary to use the Spin Echo Mapping technique to obtain the complete NMR information. The technique has proved to be particularly interesting as it permits us to distinguish between various V4+ phases. The observed frequency shift is proportional to the atomic magnetic susceptibility of the material and, therefore, changes with temperature. For V4+ phases, we have observed that the inverse shift was proportional to temperature in the working temperature range and that good estimations of the Weiss temperatures could be obtained. Moreover, at low temperature, the 31P NMR spin echo mapping of the pyrophosphate (VO)2P2O7 showed four distinct peaks that could be assigned to various unpaired electron spin densities on the phosphorus atoms. This has been correlated with previous structural determinations, particularly the oxidation state of vanadium ions in these solids. We have also observed that the inverse of the line width increased linearly with temperature in the working range. Special attention was given to VPO4 where both the evolution with temperature of the observed shift and the line width were very different from those observed on V4+ phases.

Catalysis↗
PubMed2003

Prolongation of insulin-induced activation of mitogen-activated protein kinases ERK 1/2 and phosphatidylinositol 3-kinase by vanadyl sulfate, a protein tyrosine phosphatase inhibitor.

Vanadium salts such as vanadyl sulfate (VS), potent inhibitors of protein tyrosine phosphatases, have been shown to mimic, augment, and prolong insulin's action. However, the molecular mechanism of responses to these salts is not clear. In the present studies, we examined if VS-induced effects on insulin action are associated with enhancement or augmentation in the activation state of key components of the insulin signaling pathway. Treatment of insulin receptor-overexpressing cells with insulin or VS resulted in a time-dependent transient increase in phosphorylation and activation of extracellular signal-regulated kinases 1 and 2 (ERK 1/2) that peaked at about 5 min, then declined rapidly to about baseline within 30 min. However, when the cells were treated with VS before stimulation with insulin, sustained ERK 1/2 phosphorylation and activation were observed well beyond 60 min. VS treatment also prolonged the insulin-stimulated activation of phosphatidylinositol 3-kinase (PI3-K), which was associated with sustained interaction between insulin receptor substrate-1 (IRS-1) and the p(85 alpha) subunit of phosphatidylinositol 3-kinase (PI3-K) in response to insulin. These data indicate that prolongation of insulin-stimulated ERK 1/2 and PI3-K activation by VS is due to a more stable complex formation of IRS-1 with the p(85 alpha) subunit which may, in turn, be responsible for its ability to enhance and extend the biological effects of insulin.

Adaptation, Physiological↗
PubMed2004

Redox behaviour of cysteine in the presence of ammonium trioxovanadate(V).

The interaction of ammonium trioxovanadate(V) with cysteine in aqueous solution was studied by cyclic voltammetry and absorption spectroscopy techniques. In the absence of cysteine, the cyclic voltammogram (CV) of ammonium trioxovanadate(V) solution in 0.1 M phosphate buffer (pH 7) gave two peaks at -0.130 V (reversible) and -0.400 V (irreversible). These peaks (-0.130 V, -0.400 V) can be attributed to V(V)/V(IV) and V(IV)/V(III) redox processes, respectively. In the presence of cysteine at low scan rate (40 mV/s), the peak at -0.780 V, which is assigned to the irreversible reduction of free cystine, was observed. In addition, the reduction peak of the disulfidic anion S(2)(2-) was seen at -0.650 V. Under aerobic conditions, the peaks of the disulfidic anion S(2)(2-) and free cystine are well separated. From electronic spectra of ammonium trioxovanadate(V) and cysteine mixtures, LMCT transition associated with V(V)-cyteine complex was obtained at 743 nm. The stoichiometry (ML(2)) and stability constant (log beta(1:2)=6.67) of V(V)-cysteine complex were determined by means of mole ratio method.

Cysteine↗
PubMed2006

Synthesis, characterization, and biological activity of oxovanadium(IV) complexes with polyalcohols.

Oxovanadium(IV) complexes of the polyalcohols sorbitol, galactitol, and mannitol, of stoichiometry Na(2)[VO(L)(2)].H(2)O, were obtained from aqueous alkaline solutions. They were characterized by elemental analysis, infrared and UV-vis spectroscopies, thermoanalytical (thermogravimetric and differential thermal analysis) data, and magnetic susceptibility measurements. The biological activities of the complexes on the proliferation, differentiation, and glucose consumption were tested on osteoblast-like cells (MC3T3E1 osteoblastic mouse calvaria-derived cells and UMR106 rat osteosarcoma-derived cells) in culture. The three complexes exerted a biphasic effect on cell proliferation, being slight stimulating agents at low concentrations and inhibitory in the range of 25-100 microM. All the complexes inhibited cell differentiation in tumor osteoblasts. Their effects on glucose consumption were also discussed. The free ligands did not show any effect on the studied biological parameters.

Alcohols↗
PubMed2006

Vanadium mediated apoptosis and cell cycle arrest in MCF7 cell line.

Vanadium is a metal widely distributed in the environment. It is also a dietary micronutrient. It has shown insulin mimetic and chemopreventive properties and has been considered as an important pharmacological agent. In this study, we evaluated the apoptogenic role of vanadium on human breast cancer cell line MCF7. Exposure of MCF7 cells to vanadium led to the induction of apoptosis in a dose-dependent manner. Percentage of apoptosis was maximum (42.5%) at the highest non-toxic dose (250 microM). It was found that vanadium treatment brought about a prominent chromatin condensation, cell cycle arrest leading to apoptosis. These apoptosis based assays demonstrate that vanadium has the potential to be developed into an anti-cancer drug in the near future.

Apoptosis↗
PubMed2004

Vanadyl sulfate ameliorates insulin resistance and restores plasma dehydroepiandrosterone-sulfate levels in fructose-fed, insulin-resistant rats.

OBJECTIVES: To elucidate whether vanadyl sulfate ameliorates the decreased dehydroepiandrosterone sulfate (DHEAS) in hyperinsulinemic rats, we evaluated plasma DHEAS, insulin and triglyceride (TG) levels in fructose-induced, insulin-resistant rats. DESIGN AND METHODS: Animals were divided into three groups: control (C), fructose fed (F-F), and vanadyl-treated fructose fed (F-T). Control animals were fed with standard chow; F-F and F-T groups fed with 66% fructose diet. F-F and C groups received tap water; F-T group received water supplemented with 0.2 mg/ml vanadyl sulfate. RESULTS: Fasting plasma glucose levels of three groups were comparable. Vanadyl treatment prevented the increase in plasma insulin and TG in the F-T group (P < 0.001) compared with the F-F group. Fructose feeding led to a decrease in plasma DHEAS in the F-F group (P < 0.001) compared with the C group. Vanadyl treatment prevented the decrease in plasma DHEAS in the F-T group (P < 0.001) compared with the F-F group. CONCLUSIONS: Our results indicated that the hyperinsulinemia in fructose-fed, insulin-resistant rats is associated with low levels of DHEAS. Vanadyl sulfate probably restores plasma DHEAS, due to the improved insulin action.

Animals↗
PubMed2005

Vaginal contraceptive activity of a chelated vanadocene.

Bis(cyclopentadienyl) complexes of vanadium (IV) or vanadocenes are rapid and potent inhibitors of human sperm motility with potential as a new class of contraceptive agents. This study sought to determine the vaginal contraceptive activity of vanadocene dithiocarbamate (VDDTC), a stable vanadocene (IV)-chelated complex, using the standard rabbit model as well as the domestic pig as a physiologically relevant animal model for contraception. In experiment I, ovulating New Zealand White does in subgroups of eight were artificially inseminated (AI) with semen mixed with VDDTC (0.01-1 mM) or vehicle. In experiment II, ovulating does in subgroups of 18 were AI at 5 and 60 min after intravaginal application of a gel with and without 0.1% VDDTC or 2% nonoxynol-9 (N-9) (Gynol II, Ortho Pharmaceutical, Raritan, NJ), and allowed to complete term pregnancy. In experiment III, seven sexually mature Duroc gilts in standing estrus were AI with and without intravaginal application of 0.1% VDDTC gel microemulsion. Exposure of rabbit semen to VDDTC at the time of artificial insemination resulted in a dose-dependent reduction in fertility. Exposure of semen to 1 mM VDDTC led to complete inhibition of fertility as assessed by the number of embryos (control 49/94 vs. VDDTC-treated 0/117, p<.0001) or the percent embryos (52% vs. 0%, respectively) based on number of embryos to corpora lutea. Intravaginal administration of 0.1% VDDTC gel microemulsion or Gynol II prior to artificial insemination significantly inhibited term pregnancy rates (88% and 62% inhibition, respectively) when compared to control gel alone. Vanadocene dithiocarbamate gel microemulsion provided 80% inhibition of fertility even when insemination was delayed until 60 min after intravaginal application of VDDTC gel microemulsion. Rabbits that delivered litters despite intravaginal exposure of semen to VDDTC via gel microemulsion had healthy offsprings with no apparent perinatal repercussions. In domestic pigs, intravaginal applications of 0.1% VDDTC gel microemulsion prior to artificial insemination led to complete inhibition of fertility as assessed by the number of embryos (control 29/52 vs. VDDTC-treated 0/44, p<.0001) or the percent embryos (56% vs. 0%, respectively) based on the number of embryos to corpora lutea. These results suggest that VDDTC is a potent contraceptive agent in vivo. Intravaginal use of VDDTC via a gel microemulsion has clinical potential as a safe alternative to currently used detergent-type contraceptives.

Administration, Intravaginal↗
PubMed2005

Protective effect of vanadyl sulfate on the pancreas of streptozotocin-induced diabetic rats.

The aim of this study is to examine from a biochemical and histological perspective, whether vanadium has a protective effect on the pancreas of diabetic rats. Male, 6-6.5 months old, Swiss albino rats were divided into four groups. Group I: control (intact) animals (n=13). Group II: control rats given vanadyl sulfate (n=5). Group III: streptozotocin-induced diabetic animals (n=11). Group IV: streptozotocin-induced diabetic animals given vanadyl sulfate (n=11). Vanadyl sulfate was given by gavage technique to rats in a dose of 100mg/kg daily for 60 days, after experimental animals were made diabetic. On day 60, the pancreas tissue and blood samples were taken from the animals. In the streptozotocin-induced diabetic group, blood glucose levels significantly increased in contrast to the loss of body weight, but vanadyl sulfate in streptozotocin-diabetic rats reduced blood glucose levels and increased both blood glutathione levels and body weight. Tissue sections were immunostained using an insulin antibody. The control group given vanadyl sulfate was no different from the other intact control group considering the insulin immunoreactivity in B cells. In pancreatic islets of the diabetic group, a decrease in the number of immunoreactive B cells was observed in comparison to the control group. On the other hand, pancreatic islets of the diabetic group given vanadyl sulfate showed a higher number of immunoreactive B cells in comparison to the diabetic group. According to the immunohistochemical and biochemical results obtained, it was concluded that vanadyl sulfate can regenerate B cells of endocrine pancreas in experimental diabetes.

Animals↗