Minireview: physiological and pharmacological properties of vanadium

Concentrations of vanadium in urine with hypertension prevalence and blood pressure levels

The associations of vanadium exposure with hypertension risk in animal studies are inconsistent. Furthermore, epidemiologic studies on this topic are scarce. We aimed to assess the associations of vanadium exposure with hypertension prevalence and blood pressure levels in a general Chinese population. We measured urinary vanadium concentrations in 1867 participants to evaluate their internal exposure levels. The associations of urinary vanadium concentrations, categorized into quartiles or treated as continuous variables by logarithm transformation (log2), with hypertension prevalence and blood pressure levels were assessed by the multivariable logistic and linear regression models, respectively. We used the restricted cubic spline model to evaluate the dose-response relationship. Compared with the bottom quartile of vanadium, participants in the third and fourth quartile had an adjusted odds ratio of 2.04 (95% CI:1.40, 2.96) and 2.08 (95% CI:1.42, 3.06) for hypertension, with a linear dose-response relationship. The corresponding number for a doubling of vanadium concentrations was 1.25 (95% CI:1.12, 1.39). Besides, a doubling of vanadium concentrations was associated with a 0.66 (95% CI: 0.01, 1.31) and 0.90 (95% CI: 0.50, 1.31) mm Hg increased systolic and diastolic blood pressure level, respectively. Vanadium exposure was associated with increased hypertension prevalence and blood pressure levels. Prospective studies are needed to confirm our findings in other populations.

Influence of vanadium on serum lipid and lipoprotein profiles: a population-based study among vanadium exposed workers

BACKGROUND

Some experimental animal studies reported that vanadium had beneficial effects on blood total cholesterol (TC) and triglyceride (TG). However, the relationship between vanadium exposure and lipid, lipoprotein profiles in human subjects remains uncertain. This study aimed to compare the serum lipid and lipoprotein profiles of occupational vanadium exposed and non-exposed workers, and to provide human evidence on serum lipid, lipoprotein profiles and atherogenic indexes changes in relation to vanadium exposure.

METHODS

This cross-sectional study recruited 533 vanadium exposed workers and 241 non-exposed workers from a Steel and Iron Group in Sichuan, China. Demographic characteristics and occupational information were collected through questionnaires. Serum lipid and lipoprotein levels were measured for all participants. The ratios of total cholesterol to high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) to HDL-C and apoB to apoA-I were used as atherogenic indexes. A general linear model was applied to compare outcomes of the two groups while controlling possible confounders and multivariate logistic regression was performed to evaluate the relationship between low HDL-C level, abnormal atherogenic index and vanadium exposure.

RESULTS

Higher levels of HDL-C and apoA-I could be observed in the vanadium exposed group compared with the control group (P < 0.05). Furthermore, atherogenic indexes (TC/HDL-C, LDL-C/HDL-C, and apoB/apoA-I ratios) were found statistically lower in the vanadium exposed workers (P < 0.05). Changes in HDL-C, TC/HDL-C, and LDL-C/HDL-C were more pronounced in male workers than that in female workers. In male workers, after adjusting for potential confounding variables as age, habits of smoking and drinking, occupational vanadium exposure was still associated with lower HDL-C (OR 0.41; 95% CI, 0.27-0.62) and abnormal atherogenic index (OR 0.38; 95% CI, 0.20-0.70).

CONCLUSION

Occupational vanadium exposure appears to be associated with increased HDL-C and apoA-I levels and decreased atherogenic indexes. Among male workers, a significantly negative association existed between low HDL-C level, abnormal atherogenic index and occupational vanadium exposure. This suggests vanadium has beneficial effects on blood levels of HDL-C and apoA-I.

Vanadium exposure-induced neurobehavioral alterations among Chinese workers

Vanadium-containing products are manufactured and widely used in the modern industry. Yet the neurobehavioral toxicity due to occupational exposure to vanadium remained elusive. This cross-sectional study was designed to examine the neurotoxic effects of occupational vanadium exposure. A total of 463 vanadium-exposed workers (exposed group) and 251 non-exposed workers (control group) were recruited from a Steel and Iron Group in Sichuan, China. A WHO-recommended neurobehavioral core test battery (NCTB) and event-related auditory evoked potentials test (P300) were used to assess the neurobehavioral functions of all study subjects. A general linear model was used to compare outcome scores between the two groups while controlling for possible confounders. The exposed group showed a statistically significant neurobehavioral alteration more than the control group in the NCTB tests. The exposed workers also exhibited an increased anger-hostility, depression-dejection and fatigue-inertia on the profile of mood states (p<0.05). Performances in the simple reaction time, digit span, benton visual retention and pursuit aiming were also poorer among exposed workers as compared to unexposed control workers (p<0.05). Some of these poor performances in tests were also significantly related to workers' exposure duration. P300 latencies were longer in the exposed group than in the control (p<0.05). Longer mean reaction times and more counting errors were also found in the exposed workers (p<0.05). Given the findings of our study and the limitations of neurobehavioral workplace testing, we found evidence of altered neurobehavioral outcomes by occupational exposure to vanadium.

An evidence-based systematic review of vanadium by the Natural Standard Research Collaboration

An evidence-based systematic review of vanadium by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Influence of vanadium supplementation on oxidative stress factors in the muscle of STZ-diabetic rats

In recent years, the role of free radical damage consequent to oxidative stress is widely discussed in diabetic complications. In this aspect, the protection of cell integrity by trace elements is a topic to be investigated. Vanadium is a trace element believed to be important for normal cell function and development. The aim of the present study was to investigate the effect of vanadyl sulfate supplementation on the antioxidant system in the muscle tissue of diabetic rats. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ, 65 mg/kg body weight) to male Swiss albino rats. The rats were randomly divided into 4 groups: Group I, control; Group II, vanadyl sulfate control; Group III, STZ-diabetic untreated; Group IV, STZ-diabetic treated with vanadyl sulfate. Vanadyl sulfate (100 mg/kg) was given daily by gavage for 60 days. At the last day of the experiment, rats were killed, muscle tissues were taken, homogenized in cold saline to make a 10% (w/v) homogenate. Body weights and blood glucose levels were estimated at 0, 30 and 60th days. Antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), as well as carbonic anhydrase (CA), myeloperoxidase (MPO) activities and protein carbonyl content (PCC) were determined in muscle tissue. Vanadyl sulfate administration improved the loss in body weight due to STZ-induced diabetes and decreased the rise in blood glucose levels. It was shown that vanadium supplementation to diabetic rats significantly decrease serum antioxidant enzyme levels, which were significantly raised by diabetes in muscle tissue showing that this trace element could be used as preventive for diabetic complications.

On-line separation/preconcentration of V(IV)/V(V) in environmental water samples with CTAB-modified alkyl silica microcolumn and their determination by inductively coupled plasma-optical emission spectrometry

A simple and selective method of flow injection microcolumn separation/preconcentration on-line coupled with inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the speciation of V(V)/(IV). Various factors affecting the separation/preconcentration of V(IV) and V(V) by conical microcolumn packed with cetyltrimethylammonium bromide (CTAB)-modified alkyl silica have been systematically investigated. It is found that V(V) was quantitatively retained by the microcolumn at pH 2.0-7.0, while V(IV) was not retained by the microcolumn at pH 2.0-3.5 but quantitatively retained at pH 5.0-7.0. The two vanadium species adsorbed by the modified adsorbent were quantitatively desorbed by 0.10 mL of 1.0 mol L(-1) HNO(3). Therefore, V(V) and total vanadium could be determined by CTAB-modified alkyl silica packed microcolumn separation/preconcentration and on-line ICP-OES detection after adjusting sample solution to pH 2.5 and 6.0, respectively, and the assay of V(IV) was realized by subtracting V(V) from total V. The detection of limit (LOD) for V(V) was 0.03 microg L(-1) with an enrichment factor of 27.9 for a 3.0 mL sample consumption. The relative standard deviations (RSDs) (C(V(V))=C(V(IV))=5.0 microg L(-1), n=9) were 4.3% and 4.0% for V(V) and total V, respectively. The developed method was validated by the determination of V(IV) and V(V) in environmental water samples.

Kinetics of inhibition of rabbit intestine alkaline phosphatase by heteroligand peroxo complexes of vanadium(V) and tungsten(VI)

The present work was undertaken to examine and compare some biologically important properties of peroxo compounds of V(V) and W(VI) containing biogenic species as ancillary ligand. New anionic peroxovanadate(V) complex of the type Na[VO(O(2))(2)(triglycine)].3H(2)O (pV1) and a molecular peroxotungstate(VI) [WO(O(2))(2)(triglycine)].3H(2)O (pW1) were synthesized and characterized for the purpose and their stability in solution was ascertained. Studies on kinetics of inhibition of alkaline phosphatase activity by the newly synthesized compounds and series of dipeptide and amino acid containing peroxo complexes of vanadium and tungsten synthesized previously by us viz., Na[VO(O(2))(2)(gly-gly)(H(2)O)].H(2)O (gly-gly = glycyl-glycine), Na[VO(O(2))(2)(asn)].H(2)O (asn = asparagine), Na[VO(O(2))(2)(gln)].H(2)O (gln = glutamine), and [WO(O(2))(2)(gly-gly)(H(2)O)].3H(2)O, revealed that each of these species is a potent mixed-type inhibitor of the enzyme. Significant difference was noted between the peroxovanadium (pV) and peroxotungsten (pW) compounds in terms of their oxidant activity with reduced glutathione.

Malignant fibrous histiocytoma associated with coxofemoral arthrodesis

The discovery of biomaterials led to their use in the manufacture of implants for biomedical applications. In vivo, no metal or alloy is completely inert. The potential toxicity of some of the metals most frequently employed in the manufacture of orthopedic implants has been reported. Their carcinogenic potential has been evaluated in experimental animal models. However, few reports have discussed the potential development of malignant tumors associated with prosthetic structures in humans. The present study documents a case of intraosseous sarcoma that developed in the vicinity of a metallic prosthesis 43 months after a coxofemoral arthrodesis with metallic pins and screws. With this report the authors seek to contribute to the understanding of the potential toxicity and risks of using metallic implants. Since metallic implants employed in the rehabilitation of osteo-muscular-articular disorders usually remain in the organism for long periods of time, the need to monitor the metallic structures and the adjacent tissues is extremely relevant.

Antidiabetic Activity of the Orally Effective Vanadyl-Poly (γ-Glutamic Acid) Complex in Streptozotocin(STZ)-induced Type 1 Diabetic Mice

Newly synthesized vanadyl-poly(γ-glutamic acid) complex (VO-γ-PGA) with a VO(O4) coordination mode was found to have potent antidiabetic activity in streptozotocin (STZ)-induced type 1 diabetic mice (STZ-mice), compared with that of a solution containing only vanadyl sulfate, VOSO 4. This was the first example of orally active vanadyl complex of γ-PGA for treating STZ-mice. To better define its efficacy, we examined here the effects of VO-γ-PGA treatment in STZ-mice by oral administration at the dose of 10 mg V/kg body mass for a longer period time than our previous study. The improvement in diabetic states in STZ-mice compared with saline-treated nondiabetic normal Std ddY mice. It was found that the elevated blood glucose levels in STZ-mice significantly decreased after 3 days and sustained the normalized blood glucose level around 180—200 mg/dL (10—11.1 mM) for the last 14 days, which is close to the blood glucose levels 100—200 mg/dL (5.6—11.1 mM) in nondiabetic normal Std ddY mice. The improvement in diabetes was strongly corelated by the improvement in oral glucose tolerance ability, glycosylated hemoglobin (HbA1c) levels and blood pressure, and serum parameters. The present results confirmed that VO-γ-PGA complex is a promising, orally active insulin-mimetic agent to treat type 1 diabetic mice.

Therapeutic Time Window and Dose Dependence of Neuroprotective Effects of Sodium Orthovanadate following Transient Middle Cerebral Artery Occlusion in Rats

Vanadium is widely distributed in the environment and exhibits various biological and physiological effects in the human body. We previously documented the neuroprotective effect of sodium orthovanadate (SOV) against in rodents i.v. injected with 2 ml/kg 50 mM SOV just after the induction of middle cerebral artery occlusion (MCAO; 0 min post-MCAO). To evaluate its potential clinical use, we determined here therapeutic time window (0, 45, and 90 min post-MCAO) and the neuroprotective dose (2 ml/kg, 12.5, 25, 37.5, and 50 mM) of SOV in rats. A single injection of 50 mM SOV at 0 or 45 min post-MCAO produced similar neuroprotective effects, and even 50 mM delivered 90 min post-MCAO exerted significant neuroprotection. Although the maximal neuroprotective effect was obtained at 50 mM SOV, 25 mM injected once and 12.5 mM delivered at 0 and 45 min post-MCAO significantly reduced the infarct volume. We also documented that SOV treatment ameliorates ischemic neuronal cell injury via the activation of both protein kinase B (Akt) and extracellular signal-regulated kinase (ERK), inhibits serum glucose, and elicits the gradual recovery of regional cerebral blood flow (rCBF) after transient MCAO in rats. To elucidate the important factor(s) involved in the neuronal protection afforded by SOV, we measured Akt and ERK activity, physiological parameters, blood glucose levels, and rCBF following various SOV treatments. In conclusion, Akt activation was the most important factor in SOV-induced neuroprotection; ERK activation, the gradual recovery of rCBF, and decreased blood glucose were weak contributors.

Metal degradation products: a cause for concern in metal-metal bearings?

In the majority of patients, orthopaedic implants are biocompatible. However, there is an increasing recognition that, in the long-term, permanent orthopaedic implants may be associated with adverse local and remote tissue responses in some individuals. These adverse effects are mediated by the degradation products of implant materials. The recent reintroduction of metal-on-metal bearings for total hip arthroplasty has heightened concerns about the biologic response to metal degradation products in light of the fact that the serum and urine metal concentrations in patients with these implants typically are higher than those seen in patients with conventional metal-on-polyethylene bearings. From previous studies of long-term metal-on-metal McKee-Farrar implants, it seems that these elevated levels may persist for the duration of the implant's lifetime. This is of particular concern in the younger and more active patient in whom life expectancy after implantation may exceed 30 years. The association of metal release from orthopaedic implants with any metabolic, bacteriologic, immunologic, or carcinogenic toxicity currently remains conjectural because cause and effect have not been established in human subjects. However, continued surveillance of patient populations with metal implants, particularly those with metal-metal bearings, is warranted.

Insulin mimetic effects of macrocyclic binuclear oxovanadium complexes on streptozotocin-induced experimental diabetes in rats

AIM

The vanadium complexes so far tested for their insulin mimetic effects are either mono- or binuclear and contain only acyclic ligands. The leaching or hydrolysis of vanadyl ions from these complexes is much easier, and hence they elicit side effects. In the present study, a new binuclear macrocyclic oxovanadium complex was synthesized, and its efficacy was studied on streptozotocin (STZ)-induced diabetic rats over a period of 30 days.

METHODS

The insulin mimetic effect of the complex was tested on the blood sugar level in the STZ-diabetic rats and on the activities of the carbohydrate-metabolizing enzymes present in the liver.

RESULTS

Administration of vanadium complex to STZ-induced diabetic rats decreased blood glucose levels from hyperglycaemic to normoglycaemic when compared to diabetic rats. The activity of carbohydrate-metabolizing enzymes such as hexokinase, glucose-6-phosphate dehydrogenase, glycogen synthase and glycogen content were increased to near normal in vanadium complex-administered diabetic rats. The biochemical studies such as assay of blood urea and glutamate oxaloacetate transaminases revealed that the complex is not toxic to the system.

CONCLUSION

The nontoxic nature of this complex may be due to the presence of the vanadyl ions in an intact macrocyclic form. Further, the vanadyl ions present in the macrocyclic binuclear oxovanadium complex are very close to each other, and this may enhance the insulin mimetic activity by synergic effect.

Effects of ammonium metavanadate on fertility and reproductive performance of adult male and female rats

Vanadium is a ubiquitous trace metal present in most plant and animal tissues. Environmental exposure to trivalent and pentavalent inorganic vanadium compounds has been related to impaired different phases of reproduction. Therefore, the effects of a pentavalent inorganic vanadium compound on general reproductive performance and fertility were investigated in male and female rats. Sexually mature male and female rats were exposed to 200 ppm ammonium metavanadate in drinking water. Male rats were exposed for 70 days, while the female rats exposed for 14 days premating, during mating, and throughout the whole length of gestation and lactation periods till weaning. The effects on male sex organ weights and fertility were evaluated at the end of exposure period. However, the effects on female fertility as well as developmental and postnatal effects were evaluated throughout the exposure period. The fertility was significantly reduced in both treated groups, with more pronounced suppressive effects in the male treated group. The number of implantation sites and the number of viable fetuses were significantly reduced in pregnant females of both treated groups. However, the number of resorptions, dead fetuses, and pre- and postimplantation losses were significantly increased. The incidence of resorptions was significantly increased in treated female group compared with untreated female group. The behavioral responses as well as fetal survival and viability indices were decreased in both treated groups during the lactation period. The incidence of these effects was more pronounced in the treated female group. The morphological, visceral, and skeletal anomalies were recorded significantly increased in fetuses of both treated groups, with more pronounced effects on fetuses of treated females. In conclusion, the exposure of adult male and female rats to ammonium metavanadate would cause adverse effects on fertility and reproduction.

Vanadate inhibits the ATPase activity and DNA binding capability of bacterial MutS. A structural model for the vanadate-MutS interaction at the Walker A motif

MutS, a member of the ABC ATPases superfamily, is a mismatch DNA-binding protein constituent of the DNA post-replicative mismatch repair system (MMRS). In this work, it is shown that the ATPase activity of Pseudomonas aeruginosa and Escherichia coli MutS is inhibited by ortho- and decavanadate. Structural comparison of the region involved in the ATP binding of E.coli MutS with the corresponding region of other ABC ATPases inhibited by vanadate, including the myosin- orthovanadate-Mg complex, showed that they are highly similar. From these results it is proposed that the orthovanadate inhibition of MutS ATPase can take place by a similar mechanism to that described for other ATPases. Docking of decavanadate on the ATP-binding region of MutS showed that the energetically more favorable interaction of this compound would take place with the complex MutS- ADP-Mg, suggesting that the inhibitory effect could be produced by a steric impediment of the protein ATP/ADP exchange. Besides the effect observed on the ATPase activity, vanadate also affects the DNA-binding capability of the protein, and partially inhibits the oligomerization of MutS and the temperature-induced inactivation of the protein. From the results obtained, and considering that vanadate is an intracellular trace component, this compound could be considered as a new modulator of the MMRS.

Vanadium in ambient air: concentrations in lung tissue from autopsies of Mexico City residents in the 1960s and 1990s

Vanadium concentrations in lung tissue were determined by atomic absorption spectrometry from autopsy specimens taken from residents of Mexico City during the 1960s and 1990s (20 males and 19 females, and 30 males and 18 females, respectively). Samples from the 1990s had significantly increased mean vanadium concentrations (mean +/- standard deviation: 1.36 +/- 0.08), compared with those from the 1960s (1.04 +/- 0.05). Concentrations were not correlated with gender, smoking habit, age, cause of death, or occupation. These findings suggest that vanadium in ambient air is increasing and it represents a potential health hazard for Mexico City residents. Air pollution monitoring efforts should include vanadium concentrations in suspended particles to follow-up the findings reported herein. Researchers need to acquire a better knowledge of the levels of airborne vanadium exposure at which risk to human health occurs.

Immobilized liposome layers for drug delivery applications: inhibition of angiogenesis

Liposomes were immobilized onto the surface of perfluorinated polymer tape samples and tissue culture polystyrene well-plates using a multilayer immobilization strategy. In the first step, a thin interfacial bonding layer with surface aldehyde groups was deposited from a glow discharge struck in acetaldehyde vapour. Polyethylenimine was then covalently bound onto the aldehyde groups by reductive amination, followed by covalent binding of NHS-PEG-biotin molecules onto the surface amine groups by carbodiimide chemistry. Next, NeutrAvidin protein molecules were bound onto the PEG-biotin layer. Finally, liposomes containing PEG-biotinylated lipids were docked onto the remaining binding sites of the surface-immobilized NeutrAvidin molecules. AFM was used to image surface-bound liposomes and revealed a density well below close packing. The release characteristics of the surface-bound liposomes were measured by the fluorescence intensity changes of carboxyfluorescein upon release. Liposomes filled with sodium orthovanadate were surface immobilized and used in two in vitro angiogenesis assays. Marked differences compared to various control samples were observed, demonstrating the utility of drug-filled, surface-bound liposomes for evoking localized, controlled biological host responses proximal to an implanted biomedical device.

Systemic metal-protein binding associated with total joint replacement arthroplasty

The distribution of titanium [Ti] and chromium [Cr] in serum protein fractions of patients with and without total joint replacements containing Cr and Ti was studied. Three groups were evaluated: 10 patients with cobalt-chromium [CoCr] alloy prostheses and known elevated levels of Cr; 10 patients with Ti containing implants and known elevated levels of Ti; and 10 age matched controls without prostheses. Metal-protein binding was also examined by adding various concentrations of Cr(+3) (CrCl(3)) to control serum. Cr and Ti were bound to serum proteins within specific molecular weight ranges in both patient groups. Two molecular weight ranges were found to bind Cr (at approximately 70 and approximately 180 kDa) in patients with CoCr alloy prostheses, whereas a single molecular weight range (at approximately 70 kDa) was found to bind Ti in patients with Ti alloy implants. This metal-protein binding was reproduced in vitro by adding CrCl(3) at concentrations of approximately 100 and 1000 ppb Cr, which is orders of magnitude higher than that contained in the serum of patients with CoCr alloy implants ( approximately 3 ppb Cr). This suggests that protein binding is initiated in the periprosthetic space where metal concentrations are typically 2-3 orders of magnitude higher than that observed systemically in the serum. In vitro, high molecular weight proteins including immunoglobulins demonstrated the highest affinity to Cr. Determination of specific protein carriers of metal degradation products is an essential component in the assessment of the long-term biological affects of total joint replacement devices.

Genotoxic studies of vanadium pentoxide (V(2)O(5)) in male mice. II. Effects in several mouse tissues

Vanadium pentoxide (V2O5) was tested for its ability to induce genotoxic damage in six different organs (liver, kidney, lung, spleen, heart, and bone marrow) of mice by using the alkaline Single Cell Gel Electrophoresis (SCGE) assay. Animals were sacrificed 24 h after i.p. administration of the vanadium pentoxide of 23.0, 11.5, or 5.75 microg/g (corresponding to the LD50, 1/2 LD50 and 1/4 LD50, respectively). In all tissues and organs evaluated (except for bone marrow), V2O5 increased the number of cells with damage. Our results showed that i.p. injection of V2O5 induced DNA damage in different organs and tissues, and that this kind of damage can be observed even 24 h after treatment. The analysis of DNA migration and the distribution of DNA damage showed that there are differences in sensitivity between organs and tissues to this compound. In addition the sensitivity of SCGE assay allows the detection of long term DNA damage and the possibility to compare it in various tissues and target organs.

Comparison of the therapeutic effects of two vanadium complexes administered at low dose on benzo[a]pyrene-induced malignant tumors in rats

The antitumor effects of low dose administration of the vanadium(III) complexes with L-cysteine (complex 1) and N-(2-mercaptopropionyl)-glycine (complex 2) were compared on benzo[a]pyrene (BaP)-induced tumors in Wistar rats. Male Wistar rats, injected with 10.0 mg of BaP, were divided into one control (C-G) and two treatment (TR-G) groups of 17 animals each. Animals of the first treatment group were administered complex 2 (TR-2 group) and those of the second group were administered complex 1 (TR-1 group) at doses of 100 microg of vanadium per os daily, starting from the day a palpable tumor was developed till their death. BaP injection induced a 100% tumor (leiomyosarcomas) development in the animals of all groups. Administration of complex 1 to the animals resulted in a significant prolongation of the mean survival time, a complete remission of 17.6% of the tumors developed, a significant reduction of the carcinogenic potency (CP) of BaP and of the tumor growth rate (TGR) in TR-1 group animals, compared to the control and the TR-2 group. In marked contrast, complex 2 failed at the doses administered to exert any significant modulation of the above mentioned parameters. Results indicate that at low (100 micro/day) concentrations of vanadium, complex 1 exerts a significant anticarcinogenic effect on experimentally-induced leiomyosarcomas in rats, whereas complex 2 has no effect when administered at the same low concentrations of vanadium.

A polymer-based drug delivery system for the antineoplastic agent bis(maltolato)oxovanadium in mice

Using vanadyl sulphate, sodium orthovanadate or bis(maltolato)oxovanadium (BMOV), Cruz TF, Morgan A, Min W (1995, Mol Cell Biochem 153: 161-166) have recently demonstrated the antineoplastic effects of vanadium in mice. In this study, the antineoplastic effects of BMOV against human tumour cell lines was confirmed, and this effect was shown to depend on the prolonged exposure of the cells to the drug. We have investigated a polymeric drug delivery system for the sustained delivery of BMOV as an antineoplastic agent in mice. The objective was to design and evaluate an injectable polymer-BMOV paste that would act as a drug implant for the slow but sustained release of BMOV in the mice. In vitro studies showed that the biodegradable polymer poly (Ghlr epsilon epsilon-caprolactone) (PCL) released BMOV in a sustained manner with rates of drug release increasing with increased loading of the drug in the polymer. In vivo studies showed that PCL-BMOV paste implants produced a concentration-dependent inhibition of MDAY-D2 tumour growth via systemic drug delivery. Further in vivo studies showed that 5% BMOV-loaded PCL (containing 20% methoxypolyethylene glycol) was effective in preventing tumour regrowth of resected RIF tumour masses in mice when the PCL-BMOV paste was applied to the resected site for localized drug delivery. The results confirm the potential of vanadium as an antineoplastic agent and show that the injectable PCL-BMOV formulation releases a chemotherapeutic dose of vanadium for the systemic treatment of whole tumours as well as the localized treatment of resected RIF tumours.

Vanadium salts as insulin substitutes: mechanisms of action, a scientific and therapeutic tool in diabetes mellitus research

Vanadium and its compounds exhibit a wide variety of insulin-like effects. In this review, these effects are discussed with respect to the treatment of type I and type II diabetes in animal models, in vitro actions, antineoplastic role, treatment of IDDM and NIDDM patients, toxicity, and the possible mechanism(s) involved. Newly established CytPTK plays a major role in the bioresponses of vanadium. It has a molecular weight of approximately 53 kDa and is active in the presence of Co2+ rather than Mn2+. Among the protein-tyrosine kinase blockers, staurosporine is found to be a potent inhibitor of CytPTK but a poor inhibitor of InsRTK. Vanadium inhibits PTPase activity, and this in turn enhances the activity of protein tyrosine kinases. Our data show that inhibition of PTPase and protein tyrosine kinase activation has a major role in the therapeutic efficacy of vanadium in treating diabetes mellitus.

Vanadium: a review of the reproductive and developmental toxicity

While the essentiality of vanadium for living organisms has yet to be established with certainty, vanadium has become an increasingly important environmental metal. Moreover, in recent years pharmacological interest in vanadium has also increased because of the hypothetical utilization of oral vanadium as an alternative therapy to parenteral insulin in diabetic patients. Adverse effects of vanadium depend on the circulating levels of this element. Among those effects, it is now well established that vanadate (V+5) and vanadyl (V+4) may be reproductive and developmental toxicants in mammals. Decreased fertility, embryolethality, fetotoxicity, and teratogenicity have been reported to occur in rats, mice, and hamsters following vanadium exposure. The reproductive vanadium toxicity, the maternal and embryo/fetal toxicity of this trace element, the perinatal and postnatal effects of vanadium, as well as the prevention by chelating agents of vanadium-induced developmental toxicity are reviewed here. The developmental effects of vanadium in pregnant diabetic rats are also summarized.

Genotoxicity of vanadium pentoxide evaluate by the single cell gel electrophoresis assay in human lymphocytes

Vanadium compounds are extensively used in modern industry and occupational exposure to high doses of Vanadium is quite common. In this study, the genotoxicity of vanadium pentoxide (V2O5) was evaluated directly in whole blood leukocytes and in human lymphocyte cultures using the single-cell gel electrophoresis assay (Comet Assay) to detect DNA damage expressed as DNA strand breaks and alkali labile sites. This chemical produces a clear dose-response in DNA migration in whole blood leukocytes and a significative positive effect only with the highest tested concentration in human lymphocyte cultures. After different recovery times the level of DNA damage returned to the control values. These results indicate that V2O5 is capable to induce DNA single-strand breaks and/or alkali-labile damage.

Membrane--vanadium interaction: a toxicokinetic evaluation

Vanadium is an important trace metal widely distributed in environment. Interaction of vanadate with skeletal muscle sarcolemma and basement membrane has been focussed. Scatchard analysis indicated the presence of more than one binding site for vanadate. Vanadate inhibits sarcolemmal and intestinal brush border membrane enzymes in a non-competitive manner. Membrane-vanadium interaction may lead to several structural and functional changes. The binding of vanadium to basement membrane may have some protective role.

Contractile effects of vanadate on aorta rings from virgin and pregnant rats

The present study was undertaken to characterize the contractile effects of vanadate on thoracic aorta rings from virgin and term-pregnant rats. Vanadate caused concentration-dependent contraction in rat aortic rings with an EC50 (concentration producing 50% maximum response) of 0.10 mM. Contractions in response to vanadate were equivalent to the ones measured with 1 microM phenylephrine. The effects of vanadate were not affected by indomethacin (up to 10 microM), an inhibitor of prostanoid cyclooxygenase, but were blocked in a concentration-dependent manner by staurosporine (0.1-1.0 microM), an inhibitor of protein kinase C. Vanadate exhibited a significant decrease of contractile responses in aorta of pregnant as compared to virgin rats. When aortic rings were bathed in presence of different concentrations of vanadate, the concentration-response curve to phenylephrine was shifted to the left, but maximum response was not affected. The potentiation of the contractions to phenylephrine by vanadate was significantly more prominent in aorta of virgin than of pregnant rats. These results suggest that the contractile effect of vanadate on rat aorta is independent of endogenous prostanoids and may be mediated by protein kinase C-dependent pathway. These results also show that the contractile response to vanadate on the rat aorta is impaired during pregnancy.

Toxicology of vanadium compounds in diabetic rats: the action of chelating agents on vanadium accumulation

The possible use of vanadium compounds in the treatment of diabetic patients is now being evaluated. However, previously to establish the optimal maximum dose for diabetes therapy, it should be taken into account that vanadium is a highly toxic element to man and animals. The toxic effects of vanadium are here reviewed. The tissue vanadium accumulation, which would mean an additional risk of toxicity following prolonged vanadium administration is also discussed. Recently, it has been shown that coadministration of vanadate and TIRON, an effective chelator in the treatment of vanadium intoxication, reduced the tissue accumulation of this element, decreasing the possibility of toxic side effects derived from chronic vanadium administration without diminishing the hypoglycemic effect of vanadium. However, previously to assess the effectiveness of this treatment in diabetic patients, a critical reevaluation of the antidiabetic action of vanadium and its potential toxicity is clearly needed.

In vitro biocompatibility, mechanical properties, and corrosion resistance of Ti-Zr-Nb-Ta-Pd and Ti-Sn-Nb-Ta-Pd alloys

There is much discussion about the toxic effect of vanadium and aluminum contained in Ti-6Al-4V alloy for prosthetic implants. The goal of the present investigation was to develop new titanium alloys with sufficient mechanical properties using more biocompatible alloying elements: zirconium, tin, niobium, tantalum, and palladium. The relative growth rates of L929 and MC3T3-E1 cells were significantly higher when cultured with the extraction of Ti-10Zr-8Nb-2Ta-0.2Pd or Ti-15Zr-4Nb-2Ta-0.2Pd alloys than when cultured with the extraction of Ti-6Al-4AV ELI alloy. The tensile strength, elongation, and reduction of area for Ti-15Sn-4Nb-2Ta-0.2Pd alloy were 989 MPa, 14.4%, and 49.3%, respectively, surpassing Ti-6Al-4V ELI alloy. (ASTM F138-84); those for Ti-15Zr-4Nb-2Ta-0.2Pd alloy were 725 MPa, 23.6% and 54.9%, respectively. More than 15% addition of tin as well as zirconium deteriorated the tensile properties. Titanium release into a 5% hydrochloric acid solution from the new titanium alloys was 20-50 micrograms/cm2 per day, though that from Ti-6Al-4V ELI alloy was 1300 micrograms/cm2 per day. The optimum alloy compositions are Ti-15Zr-4Nb-2Ta-0.2Pd and Ti-15Sn-4Nb-2Ta-0.2Pd, judging from cytocompatibility, corrosion resistance, and mechanical properties. The former is characterized by its higher level cytocompatibility and corrosion resistance, while the latter is characterized by mechanical properties.

Regulation of vascular and gastric smooth muscle contractility by pervanadate

1. The contractile actions of vanadate (VO4) and pervanadate (PV, peroxide(s) of vanadate) were studied in rat gastric longitudinal muscle strips and in aortic rings. The roles of extracellular sodium and calcium were evaluated and the potential effects of nerve-released agonists were considered. The possibility that these responses were due to the potentiation of tyrosine kinase activity, as a result of PV-mediated tyrosine phosphatase inhibition was explored with the use of tyrosine kinase inhibitors (genistein, tyrphostin) and by Western blot analysis of phosphotyrosyl proteins in PV-treated tissues. The ability of PV to mimic the action of the tyrosine kinase receptor-associated agonist, epidermal growth factor-urogastrone (EGF-Uro), in the gastric preparation was also studied. 2. PV caused concentration-dependent contractions in both gastric and aorta-derived tissues, with a potency that was 1 to 2 orders of magnitude greater than that of VO4. 3. Although repeated exposure of gastric and aortic tissues to a fixed concentration of VO4 caused reproducible contractions in both tissues, repeated exposure of gastric tissue to PV caused an increased contractile response plateauing after 3 exposures. In contrast, a single exposure of aortic tissue to PV (20 microM) caused a prolonged desensitization of the tissue to the subsequent contractile actions of PV or other agonists. 4. The contractile responses to PV were unaffected in both preparations by tetrodotoxin, atropine, yohimbine and phenoxybenzamine; and in the aortic preparation, the responses to VO4 and PV were the same in the presence or absence of a functional endothelium. 5. PV-induced contractions in both tissues were observed in the absence of extracellular sodium but required extracellular calcium and were attenuated by 1 micro M nifedipine.6. In the gastric preparation, the characteristics of the contractile actions of PV paralleled those of EGF-Uro in terms of (1) inhibition by genistein, (2) inhibition by indomethacin and (3) a requirement for extracellular calcium. These response characteristics differed from those of other contractile agonists such as carbachol.7. In both the gastric and aortic preparations genistein was able to inhibit PV-induced contractions selectively without causing comparable inhibition of KCI-induced contractions. Tyrphostin (AG18) also selectively blocked PV-induced contractions in the gastric, but not in the aortic preparation.8. In both the gastric and aortic tissue, in step with an increased contractile response, PV caused increases in tissue phosphotyrosyl protein content, as detected by Western blot analysis using a monoclonal antiphosphotyrosine antibody; the increases in phosphotyrosyl protein content were reduced when tissues were treated with PV at the same time as a tyrosine kinase inhibitor.9 PV, at sub-contractile concentrations, potentiated the contractile action of angiotensin II in both the gastric and aorta tissue.10 We conclude that the growth factor-mimetic agent, PV, is a much more potent contractile agonist than V04 in both vascular and gastric smooth muscle tissue. PV can cause enhanced tissue phosphotyrosyl protein content most likely via the inhibition of tissue protein tyrosine phosphatases. The contractile actions of PV, which require extracelullar calcium and are independent of extracellular sodium, would appear not to be due either to Na+/Ca2" exchange, promoted by Na+/K+-ATPase inhibition or to the inhibition of Ca2+-ATPase and might be best explained by the ability of PV, via tyrosine phosphatase inhibition, to potentiate a tyrosine kinase pathway linked to calcium entry and to the contractile process.

Investigation into vanadate-induced potentiation of smooth muscle contractility in the rabbit isolated ileum

The action of sodium orthovanadate (Na3VO4) on spontaneous mechanical activity of the longitudinal muscle was investigated in isolated segments of rabbit distal ileum. Vanadate (0.3-1000 microM) concentration-dependently enhanced the amplitude of phasic contractions (pendular movements) and caused the muscle tone to slightly increase at the highest concentrations. Both these effects were mimicked by the Ca2+ channel activator BAY K 8644 (10-1000 nM). Vanadate- and BAY K 8644-induced potentiation of mechanical activity was antagonized by the Ca2+ entry blocker nifedipine (3 nM). In Ca(2+)-free, K(+)-depolarized preparations, vanadate (100 microM) failed to contract the musculature, but potentiated the contractile response to applied calcium (CaCl2: 30-300 microM). The action of vanadate was similar to that of BAY K 8644 (3 nM) and was antagonized by nifedipine (0.1 nM). These results suggest that extracellular calcium is required for vanadate-induced smooth muscle excitation which, at least in part, appears to arise from facilitation of calcium influx through voltage-dependent Ca2+ channels.

Prevention by Tiron (sodium 4,5-dihydroxybenzene-1,3-disulfonate) of vanadate-induced developmental toxicity in mice

Vanadate is embryotoxic and fetotoxic in golden hamsters, mice and rats. Tiron (sodium 4,5-dihydroxybenzene-1,3-disulfonate), a chelating agent widely used in analytical chemistry, is an effective antidote in the treatment of oral or parenteral vanadate poisoning. The present study evaluated the effect of administration of Tiron on sodium metavanadate (NaVO3)-induced developmental toxicity in mice. NaVO3 (25 mg/kg, i.p.) was injected on day 12 of gestation, whereas Tiron was injected subcutaneously at 0, 24, 48, and 72 hr after NaVO3 administration. Tiron effectiveness was assessed at dosage levels of 0, 250, 500, and 1,000 mg/kg. Cesarean sections were performed on gestation day 18. All live fetuses were examined for external, internal, and skeletal malformations and variations. Amelioration by Tiron of NaVO3 developmental toxicity was evidenced by a significant decrease in the number of resorbed fetuses, an increase in the mean fetal weight, and a reduction in the incidence of the skeletal variations caused by NaVO3. According to these results, Tiron offers encouragement with regard to its therapeutic potential for pregnant women exposed to vanadate. However, further investigations, including the effect of increasing the time interval between acute vanadate exposure and initiation of Tiron therapy, are required.

Embryotoxic and teratogenic effects of intraperitoneally administered metavanadate in mice

Metavanadate was evaluated for developmental toxicity in pregnant Swiss mice. Sodium metavanadate (NaVO3) was administered intraperitoneally on d 6-15 of gestation at doses of 0, 2, 4, or 8 mg/kg/d. On gestation d 18, all live fetuses were examined for external, visceral, and skeletal malformations and variations. Maternal toxicity was observed at 2, 4, and 8 mg/kg/d as evidenced by decreased weight gain during treatment. Increased resorptions and dead fetuses, increased percentage postimplantation loss, and reduced fetal body weight per litter were observed at 4 and 8 mg/kg/d. There were no significant increases in the type or incidence of external and skeletal anomalies, but a significant increase in the incidence of cleft palate was detected at 8 mg/kg/d. The lowest-observed-adverse-effect level (LOAEL) for maternal toxicity was 2 mg NaVO3/kg/d, while 2 mg/kg/d was also the no-observed-adverse-effect level (NOAEL) for significant developmental toxicity.

Haematological effects of vanadium on living organisms

Although vanadium has been of great interest for many researchers over a number of years, its biochemical and physiological role is not yet fully clear. There are many papers describing the haematological consequences of its excess in living organisms and most of their data are quoted in this mini-review. The authors of these papers used various laboratory animals, different vanadium compounds, frequently different routes of administration and duration of intoxication. Hence a checklist and comparison of the results are rather difficult. Vanadium reduces the deformability of erythrocytes, and such cells are rather frequently retained in the reticuloendothelial system of the spleen and eliminated faster from the blood stream (Kogawa et al., 1976). Vanadium produces peroxidative changes in the erythrocyte membrane, this leading to haemolysis. Therefore, the depressed erythrocyte count in animals intoxicated with vanadium may be the consequence of both the haemolytic action of vanadium and the shortened time of survival of erythrocytes. Changes of the haem precursor level in blood serum and urine observed in humans exposed occupationally to vanadium suggest an influence of this element on haem synthesis. This problem requires, however, further studies and observations. Changes occurring under the influence of vanadium on the leukocyte system of animals suggest the influence of this element on the resistance of the organism, but the mechanism of the action of vanadium still requires elucidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Vanadium redox cycling, lipid peroxidation and co-oxygenation of benzo(a)pyrene-7,8-dihydrodiol

Mechanism of lipid peroxidation triggered by vanadium in human term placental microsomes was reinvestigated in vitro. Production of lipid peroxyl radicals was estimated from co-oxygenation of benzo(a)pyrene and benzo(a)pyrene-7,8-dihydrodiol. Vanadyl(IV), but not vanadate(V) caused a dose-dependent co-oxygenation. Vanadate(V) required the presence of reduced nicotinamide adenine dinucleotide phosphate to trigger co-oxygenation of benzo(a)pyrene-7,8-dihydrodiol. To determine the role of pre-formed lipid hydroperoxides, the results obtained with partially peroxidized linoleic acid were compared with those of fresh linoleate. Superoxide dismutase inhibited the co-oxygenation of reaction when fresh linoleic acid was used. To further characterize the role of superoxide anion-radical in the vanadium redox cycling, the increase of optical density of vanadate(V) dissolved in Tris buffer was measured at 328 nm during the addition of KO2. The rate of this reaction producing peroxy-vanadyl complex was decreased by superoxide dismutase, especially, in the presence of catalase. It is suggested that vanadium catalyzes two separate processes, both leading to enhanced lipid peroxidation: (i) initiation, dependent on superoxide and triggered by peroxy-vanadyl; (ii) propagation, dependent on pre-formed lipid hydroperoxide not sensitive to superoxide dismutase. It is postulated that the vanadium-triggered initiation of lipid peroxidation may be crucial for toxicity in organs with limited endogenous lipid peroxidation.

Characterization of oxygen free radicals generated during vanadate-stimulated NADH oxidation

The oxidation of NADH and accompanying reduction of oxygen to H2O2 stimulated by polyvanadate was markedly inhibited by SOD and cytochrome c. The presence of decavanadate, the polymeric form, is necessary for obtaining the microsomal enzyme-catalyzed activity. The accompanying activity of reduction of cytochrome c was found to be SOD-insensitive and therefore does not represent superoxide formation. The reduction of cytochrome c by vanadyl sulfate was also SOD-insensitive. In the presence of H2O2, all the forms of vanadate were able to oxidize reduced cytochrome c, which was sensitive to mannitol, tris and also catalase, indicating H2O2-dependent generation of hydroxyl radicals. Using ESR and spin trapping technique only hydroxyl radicals, but not superoxide anion radicals, were detected during polyvanadate-dependent NADH oxidation.

Developmental toxicity evaluation of orthovanadate in the mouse

Sodium orthovanadate in deionized water was administered once daily by gavage on gestational days 6-15 to mice at doses of 0, 7.5, 15, 30, and 60 mg/kg. Dams were killed on day 18 of pregnancy, and fetuses were examined for external, visceral, and skeletal defects. Maternal toxicity was observed at the highest doses of sodium orthovanadate, as evidenced by a significant number of deaths (60 and 30 mg/kg/d) and reduced weight gain and food consumption (30 and 15 mg/kg/d). Embryolethality and teratogenicity were not observed at maternally toxic doses and below, but fetal toxicity was evidenced by a significant delay in the ossification process of some skeletal districts at 30 mg/kg/d. The no-observed-adverse-effect level (NOAEL) for maternal toxicity was 7.5 mg/kg/d, and 15 mg/kg/d represented a NOAEL for developmental toxicity in mice under the conditions of this study.

Decavanadate acts like an alpha-adrenergic agonist in redistributing protein kinase C activity

Perfusion of rat livers with polyvanadate, but not metavanadate, was found to increase in plasma membrane and decrease in cytosol protein kinase C activity, similar to that obtained with phenylephrine, an alpha-adrenergic agonist. The effect was prevented by phenoxybenzamine, but not by propranolol implicating alpha-adrenergic receptor activation. Comparison of crystal structures of decavanadate and nonadrenaline revealed the occurrence of a structural feature of O-O-O(N) with distances of 5.5 A and 2.9 A.

Developmental toxicity of vanadium in mice after oral administration

Vanadium, as vanadyl sulphate pentahydrate, was evaluated for its embryotoxic, fetotoxic and teratogenic potential in Swiss mice. The compound was administered by gavage to pregnant mice at doses of 0, 37.5, 75 or 150 mg kg-1 day-1 on days 6-15 of pregnancy. On gestation day 18, all live fetuses were examined for external, visceral and skeletal malformations and variations. Maternal toxicity was observed in the vanadium-treated animals, as evidenced by reduced weight gain, reduced body weight on gestation day 18 (corrected for gravid uterine weight) and decreased absolute liver and kidney weights at 75 and 150 mg kg-1 day-1. The number of total implants, live and dead fetuses, late resorptions, the sex ratio and the post-implantation losses were not significantly different between the vanadium-treated mice and the controls. However, there was a significant increase in the number of early resorptions per litter at all dose levels. Fetotoxicity was evidenced by lower fetal weights and fetal lengths, and the presence of developmental variations. Malformation incidence also was increased by the administration of vanadium. Thus, the 'no observable effect level' (NOEL) for maternal toxicity, embryofetotoxicity and teratogenicity for vanadyl sulphate pentahydrate under these test conditions was below 37.5 mg kg-1 day-1 for Swiss mice.

Chelating agents in the treatment of acute vanadyl sulphate intoxication in mice

Eighteen chelating or reducing agents were tested to determine their relative efficacy as antagonists in acute intramuscular vanadyl sulphate intoxication in mice. The chelating or reducing agents were administered intraperitoneally to male Swiss mice at doses equal to one-fourth of their respective LD50. Therapeutic effectiveness (TEF) was calculated. In a subsequent experiment, the effect of EDTA, glutathione, DFOA, ascorbic acid, succinic acid, monosodium phosphate, Tiron, DTPA, and 2-mercaptosuccinic acid on the excretion, and distribution of vanadium was determined. Of the compounds examined, Tiron followed by ascorbic acid, and 2-mercaptosuccinic acid were effective in increasing the urinary excretion of vanadium. Tiron, and 2-mercaptosuccinic acid were also effective in reducing the concentration of vanadium found in kidney, the main target organ of vanadium accumulation. Tiron appears to be the most effective agent of those tested in the prevention of acute vanadium (IV) intoxication in mice.

Peripheral erythrocyte levels, hemolysis and three vanadium compounds

Three vanadium compounds of different valence states were administered to adult mice. Two, four, and eight days following treatment of vanadium, cardiac blood was collected. The blood sample was used to ascertain the peripheral erythrocyte count (cell/mm3) and to determine the in vitro hemolytic index of erythrocytes obtained from mice treated in vivo with either the tri-, tetra-, or pentavalent vanadium compound. Data indicate that the tetravalent form was the most effective test substance in 1) promoting rupture of isolated erythrocytes compared to red cells retrieved from control mice and 2) depressing the erythrocyte count obtained from heart blood; maximum effects were manifest four days post-treatment. For all treatments there appeared to be a good correlation between the degree of vanadium-induced hemolysis and the peripheral erythrocyte count reduction following exposure to the vanadium.

Redistribution of subcellular calcium in rat liver on administration of vanadate

Mitochondria isolated from the livers of rats administered with sodium meta-, ortho-, or polyvanadate, but not vanadyl sulphate, exhibited enhanced Ca2+ -stimulated respiration and uptake of calcium. These effects were shown also by mitochondria isolated from livers perfused with polyvanadate. The concentration of acid-soluble calcium decreased significantly in the mitochondrial fraction on vanadate treatment, while that in the cytosol showed a corresponding increase. Phenoxybenzamine, an antagonist to alpha-adrenergic receptors, effectively inhibited vanadate-induced Ca2+ mobilization, but surgical sympathectomy was without effect. This is the first demonstration of vanadate mimicking alpha-adrenergic agonists in vivo.

Urinary vanadium as a biological indicator of exposure to vanadium

Vanadium was determined in urine and blood of two workers (Worker Nos. 1 and 2 with direct exposure to vanadium pentoxide) and 13 fellow workers (with indirect or no vanadium exposure), and the results were compared by means of personal and stationary sampling of vanadium in air. Worker No. 1, a foreman with the heaviest exposure to vanadium, had a green tongue, complained of frequent productive coughing, and excreted 47 to 124 ng/ml vanadium in his late morning and mid-afternoon urine. Worker No. 2, a helper to the foreman with less exposure, had no green tongue or subjective complaints, and excreted no vanadium at a measurable level even in his mid-shift urine. No vanadium was detected in urine samples from other workers, nor in blood from all workers including Worker Nos. 1 and 2. Application of inductively coupled plasma emission spectrometry to measurement of vanadium in biological materials is discussed.

Some selected peripheral blood and haemopoietic system indices in Wistar rats with chronic vanadium intoxication

1. Wistar rats of both sexes received vanadium in drinking water in the amount of 23-29 mg/kg body weight in the form of ammonium metavanadate (AMV) for a period of 2, 4 and 8 weeks. 2. Animals treated in this way ate less food and drank less AMV solution as compared with the amount of water consumed by the controls; they suffered from diarrhoea, and owing to this the increment in body weight was reduced. 3. Vanadium decreased erythropoiesis and maturation of red blood cells, which was expressed by a reduced erythrocyte count and haemoglobin level and increased reticulocyte and polychromatophilic erythrocyte count in the peripheral blood. 4. The composition percentage of the bone marrow cells and the peripheral blood leukocyte count did not undergo noticeable changes under the influence of vanadium.

Vanadium and lipid peroxidation: evidence for involvement of vanadyl and hydroxyl radical

The present study was designed to determine which form of vanadium is involved in initiating conjugated diene formation in both purified and partially peroxidized fatty acids, and to determine if active oxygen radicals are involved in this process. We report that vanadyl is the active form of vanadium in initiating conjugated diene formation in micelles prepared from purified fatty acids or partially peroxidized fatty acids. Vanadate did not initiate conjugated diene formation in either case. Hydroxyl radicals were shown to be involved in the initiation of diene conjugation when vanadyl and hydrogen peroxide were added together in a reaction mixture. In this case, there was a rapid burst of conjugated diene formation which quickly leveled off. Using spin trapping techniques, hydroxyl radicals were shown to be generated in the vanadyl-catalyzed break-down of fatty acid hydroperoxides. A comparison was made between the ability of vanadyl or vanadyl chelates to decompose hydrogen peroxide and catalyze the decomposition of fatty acid hydroperoxides. It was found that strongly chelated vanadyl (vanadyl/EDTA) was much less effective in decomposing both hydrogen peroxide and fatty acid hydroperoxides than the weak vanadyl chelates (e.g., vanadyl/ADP). This study suggests a mechanism to explain the effects of vanadium on lipid peroxidation.

Histamine secretion from mast cells stimulated with sodium orthovanadate

Sodium orthovanadate was found to be an effective histamine liberator from peritoneal mast cells of the rat and mouse. The release process was slow, non-cytotoxic and strongly dependent on pH and extracellular calcium. The effect was highly tissue and species specific and human basophil leucocytes and tissue mast cells of the rat and guinea pig were only weakly responsive or essentially unreactive.