Vanadium compounds and cellular death mechanisms in the A549 cell line: The relevance of the compound valence.

Non-small lung cell carcinoma has a high morbidity and mortality rates. The elective treatment for stage III and IV is cisplatinum that conveys serious toxic side effects. Vanadium compounds are metal molecules with proven antitumor activity that depends on its valence. Therefore, a better understanding of the mechanism of action of vanadium compounds is required. The aim of our study was to investigate the mechanisms of cell death induced by sodium metavanadate (NaVO3 [V(+5)]) and vanadyl sulfate (VOSO4 [(+4)]), both of which have reported apoptotic-inducing activity. We exposed the A549 cell line to various concentrations (0-100 µM) and to different exposure times to each compound and determined the cell viability and expression of caspases, reactive oxygen species (ROS) production, Bcl2, Bax, FasL and NO. Our results showed that neither compounds modified the basal expression of caspases or pro- and anti-apoptotic proteins. The only change observed was the 12- and 14-fold significant increase in ROS production induced by NaVO3 and VOSO4 , respectively, at 100 µm concentrations after 48 hours. Our results suggest that classical apoptotic mechanisms are not related to the cell death induced by the vanadium compounds evaluated here, and showed that the higher ROS production was induced by the [(+4)] valence compound. It is possible that the difference will be secondary to its higher oxidative status and thus higher ROS production, which leads to higher cell damage. In conclusion, our results suggest that the efficacy of the cell death mechanisms induced by vanadium compounds differ depending on the valence of the compound.

Astrogliosis and HSP 70 activation in neonate rats' brain exposed to sodium metavanadate through lactation.

The effect of sodium metavanadate (NaVO3) exposure on lipid oxidative damage in the CNS of suckling rats was studied. Using histological markers of cellular injury, we also studied the morphological alterations of neurons and astroglial cells in different regions of neonate rats CNS after NaVO3 exposure. Dams of treated litters were intraperitoneally injected with 3mgNaVO3/kgbody weight/day during 12days starting on post-natal day (PND) 10. On the 21st PND, four pups of each litter were sacrificed by decapitation and six brain areas were removed for lipid peroxidation assay by the thiobarbituric acid (TBA) reaction, the other four were transcardially perfused-fixed and their brains were removed and cut with a cryostat. Brain sections were processed for: NADPHd histochemistry and anti-HSP70, anti-GFAP and anti-S100 immunohistochemistry. The relative optical density of the NADPHd stained layers and of S100 (+) astrocytes and the GFAP (+) astrocyte surface area in Cer and Hc were measured. Although MDA levels, S100 immunostaining and NADPHd activity didn't show differences between experimental and control groups, both astrogliosis and HSP70 activation were detected in Cer, while only the former was detected in Hc of V-exposed pups.

Effects of sodium metavanadate on in vitro neuroblastoma and red blood cells.

Toxicity of vanadium on cells is one of the less studied effects. This prompted us to study the structural effects induced on neuroblastoma and erythrocytes by vanadium (V) sodium metavanadate. This salt was incubated with mice cholinergic neuroblastoma cells and intact human erythrocytes. To learn whether metavanadate interacts with membrane lipid bilayers it was incubated with bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE). These are phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. Exposure of neuroblastoma cells to metavanadate showed significant decreases in cell viability as well as in cell number correlating with inhibition of aconitase activity. In scanning electron microscopy (SEM) and defocusing microscopy (DM) it was observed that induced on erythrocytes the formation of echinocytes. However, no effects were obtained when metavanadate was made to interact with DMPC and DMPE multibilayers and liposomes, assays performed by X-ray diffraction and differential scanning calorimetry (DSC), respectively. These results imply that the effects of metavanadate on erythrocytes are through interactions with proteins located in the membrane outer moiety, and could still involve other minor lipid components as well. Also, partly unsaturated lipids could interact differently the fully saturated chains in the model systems.

The role of silver and vanadium release in the toxicity of silver vanadate nanowires toward Daphnia similis.

Nanomaterials are used in a wide spectrum of applications, including nanowires that are objects with at least one of its dimensions in the range of 1 to 100 nm. Recently, a new type of silver vanadate nanowire decorated with silver nanoparticles (SVSN-LQES1) with promising antimicrobial activity against different pathogenic bacteria was described. The objective of the present study was to evaluate the role of silver and vanadium release in the acute toxicity of this material using Daphnia similis. To verify the effect of the presence of the nanowires in the test solution, tests were performed before and after filtration. Total silver release to the testing media was determined using the method of inductively coupled plasma atomic emission spectroscopy (ICP-AES). Silver vanadate nanowires decorated with silver nanoparticles (SVSN-LQES1) are acutely toxic to D. similis. The release of silver from the nanomaterial trapped in the gut along with the silver released to the test media seems to be responsible for the observed toxicity. Although toxic to Daphnia, vanadium does not contribute to the toxicity of SVSN-LQES1. The observed increase in lipid droplets appears to be related to the exposure of the organisms to the nanomaterials, but the significance of this response needs further investigation.

Hydroxylamido-amino acid complexes of oxovanadium(V). Toxicological study in cell culture and in a zebrafish model.

Oxovanadium(V) complexes [VO(NH(2)O)(2)(val)] and [VO(NH(2)O)(2)(met)] caused inhibition of cell proliferation in two osteoblast cell lines, MC3T3-E1 and UMR106, as well as the viability of zebrafish eggs. In MC3T3-E1, both compounds inhibited cell proliferation (up to ca. 40% at 25 µM [VO(NH(2)O)(2)(val)] and 25% at 25 µM [VO(NH(2)O)(2)(met)]). This effect occurs in a dose response manner from 2.5 µM (p < 0.01) with a more deleterious action of [VO(NH(2)O)(2)(met)]. In UMR106 tumoral cells, [VO(NH(2)O)(2)(val)] inhibited cell proliferation up to 75% from 25 µM while [VO(NH(2)O)(2)(met)] behaved as an inhibitory agent in the whole range of concentrations (p < 0.01). Similar toxic effects were obtained from morphological studies in cell cultures. Moreover, the IC(50) values for both complexes in culture studies correlated with the IC(50) values obtained with an in vivo model of toxicity (FET test). Besides, the cytotoxicity evaluation in cell culture showed a decrease in mitochondrial activity which was stronger for [VO(NH(2)O)(2)(met)] than for [VO(NH(2)O)(2)(val)] (44% vs. 58% at 25 µM) in both cell lines (p < 0.001). Genotoxicity assessed by micronuclei induction also showed a stronger effect of [VO(NH(2)O)(2)(met)] in both cell lines. Besides, [VO(NH(2)O)(2)(val)] caused DNA damage determined by comet formation in MC3T3-E1 cells in the range of 2.5-25 µM, while this effect could not be observed in the osteosarcoma cells. On the other hand, [VO(NH(2)O)(2)(val)] enhanced ROS levels over basal up to 225% and 170% at 100 µM in MC3T3-E1 and UMR106 cells, respectively (p < 0.01). For [VO(NH(2)O)(2)(met)] a similar situation was observed, suggesting an important role for oxidative stress in the toxicity mechanism of action. Although both complexes showed interesting results that would deserve further drug development [VO(NH(2)O)(2)(val)] was more stable than [VO(NH(2)O)(2)(met)] in the solid state. Therefore, we consider that [VO(NH(2)O)(2)(val)] is a good candidate to be tested in in vivo models as a potential antitumoral agent.

Cyto- and genotoxicity of a vanadyl(IV) complex with oxodiacetate in human colon adenocarcinoma (Caco-2) cells: potential use in cancer therapy.

The complex of vanadyl(IV) cation with oxodiacetate, VO(oda) caused an inhibitory effect on the proliferation of the human colon adenocarcinoma cell line Caco-2 in the range of 25-100 µM (P < 0.001). This inhibition was partially reversed by scavengers of free radicals. The difference in cell proliferation in the presence and the absence of scavengers was statistically significant in the range of 50-100 µM (P < 0.05). VO(oda) altered lysosomal and mitochondria metabolisms (neutral red and MTT bioassays) in a dose-response manner from 10 µM (P < 0.001). Morphological studies showed important transformations that correlated with the disassembly of actin filaments and a decrease in the number of cells in a dose response manner. Moreover, VO(oda) caused statistically significant genotoxic effects on Caco-2 cells in the low range of concentration (5-25 µM) (Comet assay). Increment in the oxidative stress and a decrease in the GSH level are the main cytotoxic mechanisms of VO(oda). These effects were partially reversed by scavengers of free radicals in the range of 50-100 µM (P < 0.05). Besides, VO(oda) interacted with plasmidic DNA causing single and double strand cleavage, probably through the action of free radical species. Altogether, these results suggest that VO(oda) is a good candidate to be evaluated for alternative therapeutics in cancer treatment.

ROS formation and antioxidant status in brain areas of rats exposed to sodium metavanadate.

In the present work, in vivo ROS formation and the activity of antioxidant enzymes in the hippocampus and the cerebellum of sodium metavanadate (NaVO3) treated rats were studied. Rats were i.p. injected with 3 mg/kg bw/day (V1 group) or with 7.2 mg/kg bw/day of NaVO3 (V2 group) for 5 consecutive days. Results show that after only 5 days of NaVO3 exposure, reactive oxygen species formation and alteration of the oxidative defence system were observed. Vanadium-induced OH production was detected in cerebellum at the high dose. This result was confirmed by in situ ROS histochemical staining. Neither Cat nor Cu-Zn SOD activities showed changes while GSH/GSSG ratio, in both brain areas, was significantly decreased in NaVO3-treated groups. The present work indicates that the NaVO3 dose and the particular brain area constitution would be critical in the cellular and molecular oxidative mechanism of this element.

Vanadate-induced cell death is dissociated from H2O2 generation.

Vanadium is an environmentally toxic metal with peculiar and sometimes contradictory cellular effects. It is insulin-mimetic, it can either stimulate cell growth or induce cell death, and it has both mutagenic and antineoplastic properties. However, the mechanisms involved in those effects are poorly understood. Several studies suggest that H(2)O(2) is involved in vanadate-induced cell death, but it is not known whether cellular sensitivity to vanadate is indeed related to H(2)O(2) generation. In the present study, the sensitivity of four cell lines from different origins (K562, K562-Lucena 1, MDCK, and Ma104) to vanadate and H(2)O(2) was evaluated and the production of H(2)O(2) by vanadate was analyzed by flow cytometry. We show that cell lines very resistant to H(2)O(2) (K562, K562-Lucena 1, and Ma104 cells) are much more sensitive to vanadate than MDCK, a cell line relatively susceptible to H(2)O(2), suggesting that vanadate-induced cytotoxicity is not directly related to H(2)O(2) responsiveness. In accordance, vanadate concentrations that reduced cellular viability to approximately 60-70% of the control (10 mumol/L) did not induce H(2)O(2) formation. A second hypothesis, that peroxovanadium (PV) compounds, produced once vanadate enters into the cells, are responsible for the cytotoxicity, was only partially confirmed because MDCK cells were resistant to both vanadate and PV compounds (10 micromol/L each). Therefore, our results suggest that vanadate toxicity occurs by two distinct pathways, one dependent on and one independent of H(2)O(2) production.

Characteristics of in vivo murine erythropoietic response to sodium orthovanadate.

Current knowledge about the effects of vanadium compounds on erythropoiesis is still reduced and even contradictory. The aim of this work was to evaluate the in vivo effects of a single dose of sodium orthovanadate (OV, 33 mg/kg i.p.) on CF-1 mice in a time course study (0-8 days). Murine erythropoiesis was assessed through a combinatory of experimental approaches. Classical peripheral and bone marrow (BM) hematological parameters were determined. Erythroid maturation in blood stream and hemopoietic tissues (59Fe uptake assays), BM erythroid progenitor frequency (clonogenic assays) and erythroid crucial protein expressions for commitment and survival: GATA-1, erythropoietin receptor (Epo-R) and Bcl-xL (immunoblottings) were evaluated. Neither BM cellularities nor BM viabilities changed noticeably during the study. Peripheral reticulocytes showed a biphasic increment on days 2 and 8 post-OV. hematocrits enhanced transiently between days 2 and 4. 59Fe uptake percentages enhanced in peripheral blood nearly two-fold over control values between 4 and 8 days (p<0.01) without changes in BM and spleen. Additionally, mature erythroid BM compartments: polychromatophilic erythroblasts and orthochromatic normoblasts increased by the eighth day. BFU-E colonies remained near basal values during the whole experience, whilst CFU-E colonies raised 60% over control at 8 days post-OV (p<0.05). GATA-1 and Epo-R were significantly over-expressed from the third until the end of the experimental protocol (p<0.01). Surprisingly, Bcl-xL showed a constitutive expression pattern without changes during the experience. Experimental data let us suggest that OV does not to cause bone marrow cytotoxicity and that it accelerates maturation of BM committed erythroid precursors. Moreover, there are significant correlations among erythroid-related protein expressions: GATA-1 and Epo-R and the frequency of CFU-E. In addition, Bcl-xL expression invariance during the time course study would indicate that the stimulatory effect of OV treatment on erythropoiesis was mainly exerted on the maturation of red cell precursors rather than on the antiapoptosis of erythroid terminal progenitors.

Vanadium (V)-induced neurotoxicity in the rat central nervous system: a histo-immunohistochemical study.

As vanadium was found to induce oxidative stress in the central nervous system, the morphological alterations of neurons and astroglial cells in adult rat central nervous system after vanadium exposure was studied, using histological markers of cellular injury. Animals were intraperitoneally injected with 3 mg/kg body weight of sodium metavanadate for 5 consecutive days. NADPH diaphorase histochemistry and heat shock protein (hsp) 70, glial fibrillary acidic protein (GFAP), and S-100 immunohistochemistry were performed in floating sections of several brain areas. NADPHd staining was higher in the molecular and granular layers of the cerebellar cortex, and small NADPHd-stained interneurons were observed in hippocampal sections in V(+5)-exposed animals. hsp 70 immunostaining showed the presence of reactive neurons in cerebellum of treated animals. GFAP and S-100 immunohistochemistry showed enlarged astrocytes in cerebellum and hippocampus in the V(+5)-exposed animals. The histological markers used showed that the main areas affected by vanadium-mediated free-radical generation were the hippocampus and the cerebellum.

Relationship between phosphatase activity and cytotoxic effect of two protein phosphatase inhibitors, okadaic acid and pervanadate, on human myeloid leukemia cell line.

Protein phosphatases are signalling molecules that regulate a variety of fundamental cellular processes including cell growth, metabolism and apoptosis. The aim of this work was to correlate the cytotoxicity of pervanadate and okadaic acid on HL60 cells and their effect on the phosphatase obtained from these cells. The cytotoxicity of these protein phosphatase inhibitors was evaluated on HL60 cells using phosphatase activity, protein quantification and MTT reduction as indices. The major phosphatase presents in the cellular extract showed high activity (80%) and affinity (Km = 0.08 mM) to tyrosine phosphate in relation to p-nitrophenyl phosphate (pNPP)-(Km = 0.51 mM). Total phosphatase (pNPP) was inhibited in the presence of 10 mM vanadate (98%), 200 microM pervanadate (95%) and 100 microM p-chloromercuribenzoate (80%) but okadaic acid caused a slight increase in enzyme activity (25%). When the HL60 cells were treated with the phosphatase inhibitors (pervanadate and okadaic acid) for 24hours, only 20% residual activity was observed in presence of 200 microM pervanadate, whereas in the presence of okadaic acid this inhibitory effect was not observed. However, in respect to mitochondrial function, cell viability decreased about 80% in the presence of 100 nM okadaic acid. The total protein content was decreased 25% when the cells were treated with 100 nM okadaic acid in combination with 200 microM pervanadate. Our results suggest that both phosphatase inhibitors presented different mechanisms of action on HL60 cells. However, their effect on the cell redox status have to be considered.

Mechanisms of vanadate-induced cellular toxicity: role of cellular glutathione and NADPH.

Besides its insulin-mimetic effects, vanadate is also known to have a variety of physiological and pharmacological properties, varying from induction of cell growth to cell death and is also a modulator of the multidrug resistance phenotype. However, the mechanisms underlying these effects are still not understood. The present report analyzes the mechanisms of vanadate toxicity in two cell lines previously found to have different susceptibilities to this compound. It was shown that catalase and GSH reversed the sensitivity of a vanadate-sensitive cell line and NADPH sensitized vanadate-resistant cells. NADPH also increased the residues of P-Tyr and the induction of Ras protein expression in vanadate-resistant cells, while GSH avoided these effects in vanadate-sensitive cells. Thus, it seems that the effects of vanadate in signal transduction are dependent on NADPH and are related to cell death. Based on the effects observed in the present study it was suggested that once inside the cell, vanadate is reduced to vanadyl in a process dependent on NADPH. Vanadyl then may react with H2O2 generating primarily peroxovanadium species (PV) rather than following the Fenton reaction. The PV compounds formed would be responsible for P-Tyr increase, Ras induction, and cell death. The results obtained also point to vanadate as a possible chemotherapic in the use of multidrug-resistant tumors.

Vanadate is toxic to adherent- growing multidrug-resistant cells.

The development of multidrug resistance (MDR) is the primary cause of failure of cancer chemotherapy and circumventing this problem is a major challenge in oncology. Vanadate is known to inhibit the ATPase activity of the P-glycoprotein and multidrug-resistant associated protein. In the present study we show that adherent MDR cells are more sensitive to vanadate than adherent non-MDR ones, but the same is not true for suspension-growing cells. Vanadate induced stress fiber in the non-MDR adherent MDCK cell line, but destroyed the actin fibers of MDCK/60 and MA104 cells, two adherent MDR cell lines, suggesting that the sensitivity of these cells to vanadate is related to their actin cytoskeleton. The results suggest that vanadate may be used as an adjuvant in the chemotherapy of solid tumors, not only as an ATPase inhibitor but also because of its effect in the MDR cell cytoskeleton.

[Genotoxic effects of vanadium compounds]. / Efectos genotóxicos de los compuestos del vanadio.

Vanadium is a metal member of the periodic table VB group, with atomic weight 59.95 and atomic number 23 and it has some oxidizing states from -1 to +5. Vanadium has many industrial uses and its contribution with environmental contamination is growing every day. In the last 10 years research about the vanadium effects on living beings, has been increasing substantially, due to its presence in the environment from different sources. Interest for vanadium and their compounds is because its toxic effects and uses in some biomedical areas: such as antineoplastic, cholesterol and glucose level blood, diuretic, oxygen haemoglobin affinity. Vanadium toxic effects are so due to the fact of its property of inhibiting many enzymatic systems. Vanadate and vanadyl ions make chemical complexes exhibiting the property of inhibiting or increasing the activity of the enzymes participating in the DNA and RNA synthesis. They also induce mutagenic and genotoxic effects. Biochemical assays show cytotoxic effects, increase in the cellular differentiation, gene expression alterations and other biochemical and metabolic alterations. Research has been done with in vitro systems, but few with laboratory animals. It is necessary to carry out more work in the field of genetic toxicology with vanadium compounds. This type of compounds may be considered mutagenic and genotoxic, with cytotoxic and aneuploidogenous effects.

[Teratogenic effect of ammonium metavanadate in Swiss albino mice]. / Efecto teratogénico del metavanadato de amonio sobre el ratón albino suizo.

Far as it is known to us, there is only one report in the medical literature dealing with the teratogenous effect of vanadium on neural structures (1): while trying to experimentally induce anencephaly in the offsprings of swiss-albino mice through the administration of ammonium metavanadate via drinking water, during different stages of their lives; a neural tube defect consisting of arrhinencephaly was obtained; various degrees of hypoplasia or aplasia of both the olfactory bulbs and tracts were evidenced, as well as congenital lesions of variable intensity in other rhinencephalic structures. The probable mechanisms through which vanadium exercises its neural teratogenous effect are analyzed.

[Teratogenic effects of ammonium metavanadate on the CNS of the offspring of albino rats. A histological and histochemical study]. / Efecto teratogénico del metavanadato de amonio en el SNC de la descendencia de ratas albinas. Estudio histológico e histoquímico.

The vanadium is a metallic oligoelement present in the majority of tissues. Its abnormal biological disposal environment can be related with its possible teratogenicity and alteration in the contents of glycosaminoglycans acids (GAGs), which participate in the morphological processes and the maturation of Central Nervous System (CNS). The proposal of the project is to analyze the teratogenic effect of ammonium metavanadate (AMV) and its action on the GAGs in the CNS of the litter of albino rats. The ammonium metavanadate was diluted in distilled water in concentration of 100 and 200 ppm, drunk by the rats since their birth and/or weaning to adult age, except during the matching and gestation. The animals control drunk water without this metal. The litter were analyzed to detect possible congenital malformations, then CNS were removed of descendents and were processed by light microscope, cuts of 6 u were stained with H/E; Alcian Blue pH 3.5 and 5.6, this last one concentrations of C12Mg from 0.05 M to until 1.0 M. Previously parallels sections were treated with testicular hyaluronidase. The macroscopic analysis of the new born rats that came from rats that received AMV in concentrations 100 and 200 ppm, resulted in congenital anomalies like unilateral hypoplasia of olfactory bulbs and cerebral hemisphere. The microscopic analysis revealed changes in the layers patron of olfactory bulbs and an increased of alcianophilia in the pH 5.6 to 0.2 M MgC12, in the extracellular matrix of CNS of rats descendents treated with AMV to the dose 200 ppm, sensibles to the testicular hyaluronidase, corresponding to hyaluronic acid (HA) and chondroitin 4 and/or 6 sulphate (C4S or C6S) of low grade of sulphation. These results suggest that the AMV given to albino rats has a teratogenic result when it is used before the gestation and for long periods of animals life that alter the of GAGs of CNS contents during the development.

[Toxic effects of ammonium metavanadate on the growth and number of the offspring of Swiss albino mice]. / Efectos tóxicos del metavanadato de amonio sobre el crecimiento y número de crías de ratones albinos suizos.

The present research show, an statistical study of the effects of ammonium metavanadate (AMV) on size, weight and number of offsprings of 56 albino swiss mice (male and female) was carried out. These mice ingested AMV in concentration of 100 and 200 ppm "ad libitum" since birth, continuing throughout breasting until mating. The control group received water free from the metal. The statistical results, obtained by the Duncan and Tukey method, were the following: a significant drop in body size in 200 ppm concentration of AMV, and in tail size in a concentrations of 100 and 200 ppm. A significant increase was observed in the number of the offsprings on the groups treated with AMV on a concentration of 200 ppm with respect to the control group.

[Changes in female reproduction induced by ammonium metavanadate in Swiss albino mice]. / Alteraciones de la reproducción femenina, inducidas por el metavanato de amonio en ratón albino suizo.

Female reproduction alterations induced by vanadium salts, taken in periods no related with mating/gestation, correlated with histological alterations has not been reported. Vanadium is a metal from VB group of periodical table, and it has been detected in high concentrations in heavy petroleum produced in this region of our country, there have not had investigations about vanadium effect on species reproduction. In this work 100 and 200 ppm doses of ammonium vanadate (A.M.V.) prepared with demineralized water were administered orally to swiss albino mice in different periods. The administration of vanadium salt was suspended before mating. Pregnant mice were allowed to deliver and a statistical analysis were performed to pregnancy percent and pups means. Non pregnant mice were killed after 21 days of mating. Uterus and ovaries were weight, luteal bodies were counted and histological samples of ovaries were prepared. The results shown a non significative increase of pregnancy (p < 1) in mice exposed from weaning to adult, for animals exposed to maximum concentrations 200 ppm a significative reduction of pregnancy (p = 0.00001), to mean pups were detected (z = 0.68), and number of luteal bodies (s = 3.3 +/- 0.5). The microscopic observation shown polycystic ovary, atresic follicular increasing, follicle in mature stage and luteal bodies; hard decreasing; hard depletion was observed in thecoluteic cells of luteal bodies. A.M.V. modify reproduction even though if exposition have been made in period before mating and pregnancy. As doses and exposition periods increase detrimental effects induces alteration in the follicular phase and luteal of ovarian cycle. Epidemiological and genetic studies are recommended in regions where vanadium concentrations are high, and the drinking water and foods are contaminated with this metal, in order to know how it affect human reproduction.

Proliferative and morphological changes induced by vanadium compounds on Swiss 3T3 fibroblasts.

Vanadium compounds are shown to have a mitogenic effect on fibroblast cells. The effects of vanadate, vanadyl and pervanadate on the proliferation and morphological changes of Swiss 3T3 cells in culture are compared. Vanadium derivatives induced cell proliferation in a biphasic manner, with a toxic-like effect at doses over 50 microM, after 24 h of incubation. Vanadyl and vanadate were equally potent at 2.5-10 microM. At 50 microM vanadate inhibited cell proliferation, whereas slight inhibition was observed at 100 microM of vanadyl. At 10 microM pervanadate was as potent as vanadate and vanadyl in stimulating fibroblast proliferation, but no effect was observed at lower concentrations. A pronounced cytotoxic-like effect was induced by pervanadate at 50 microM. All of these effects were accompanied by morphological changes: transformation of fibroblast shape from polygonal to fusiform; retraction with cytoplasm condensation; and loss of lamellar processes. The magnitude of these transformations correlates with the potency of vanadium derivatives to induce a cytotoxic-like effect: pervanadate > vanadate > vanadyl. These data suggest that the oxidation state and coordination geometry of vanadium determine the degree of the cytotoxicity.