Novel pH responsive supramolecular hydrogels of chitosan hydrochloride and polyoxometalate: In-vitro, in-vivo and preliminary safety evaluation.

In the current study, electrostatically-driven pH responsive, supramolecular hydrogels of the trilacunary Wells-Dawson-type 15-tungsto-2-phosphate polyanion (P2W15) and chitosan hydrochloride (ChCl) were prepared, using methacrylic acid as pH responsive agent using benzoyl peroxide (BPO) as initiator. The prepared hydrogels were characterized by FT-IR, SEM, XRD and thermal analyses (TGA-DSC). The swelling and pH based P2W15 release profile of the hydrogels showed maximum swellability and release at pH 7.4. Different mathematical models were applied, showing that P2W15 release followed supercase transport-II mechanism and zero-order kinetics. The cytotoxicity results showed that free and embedded P2W15 exhibited dose-dependent cytotoxicity against cancer cell lines (MCF-7; HeLa) with minimal effects on normal cells (Vero). The developed hydrogels were administered to the rabbits for determining the pharmacokinetic behavior of the polyanion. Moreover, the developed hydrogel system as well as polyanion concentration used were also checked for its oral tolerability and safety evaluation in rabbits. The histopathological studies, serum chemistry (except blood glucose level) and hematological investigations exhibited that administered hydrogel suspension at maximal tolerable dose (4000mg/kg body weight) and polyanion concentration used (20mg) were safe from in-vivo point of view. The developed hydrogels exhibited desirable qualities of a drug delivery system that can be used for the delivery of the embedded polyanion.

Ultrasmall, water dispersible, TWEEN80 modified Yb:Er:NaGd(WO4)2 nanoparticles with record upconversion ratiometric thermal sensitivity and their internalization by mesenchymal stem cells.

This work presents the synthesis by coprecipitation of diamond shaped Yb:Er:NaGd(WO4)2 crystalline nanoparticles (NPs) with diagonal dimensions in the 5-7 nm × 10-12 nm range which have been modified with TWEEN80 for their dispersion in water, and their interaction with mesenchymal stem cells (MSCs) proposed as cellular NP vehicles. These NPs belong to a large family of tetragonal Yb:Er:NaT(XO4)2 (T = Y, La, Gd, Lu; X = Mo, W) compounds with green (2H11/2 + 4S3/2 â†’ 4I15/2) Er-related upconversion (UC) efficiency comparable to that of Yb:Er:ß-NaYF4 reference compound, but with a ratiometric thermal sensitivity (S) 2.5-3.5 times larger than that of the fluoride. At the temperature range of interest for biomedical applications (∼293-317 K/20-44 °C) S = 108-118 × 10-4 K-1 for 20 at%Yb:5 at%Er:NaGd(WO4)2 NPs, being the largest values so far reported using the 2H11/2/4S3/2 Er intensity ratiometric method. Cultured MSCs, incubated with these water NP emulsions, internalize and accumulate the NPs enclosed in endosomes/lysosomes. Incubations with up to 10 µg of NPs per ml of culture medium maintain cellular metabolism at 72 h. A thermal assisted excitation path is discussed as responsible for the UC behavior of Yb:Er:NaT(XO4)2 compounds.

Tin Tungstate Nanoparticles: A Photosensitizer for Photodynamic Tumor Therapy.

The nanoparticulate inorganic photosensitizer ß-SnWO4 is suggested for photodynamic therapy (PDT) of near-surface tumors via reiterated 5 min blue-light LED illumination. ß-SnWO4 nanoparticles are obtained via water-based synthesis and comprise excellent colloidal stability under physiological conditions and high biocompatibility at low material complexity. Antitumor and antimetastatic effects were investigated with a spontaneously metastasizing (4T1 cells) orthotopic breast cancer BALB/c mouse model. Besides protamine-functionalized ß-SnWO4 (23 mg/kg of body weight, in PBS buffer), chemotherapeutic doxorubicin was used as positive control (2.5 mg/kg of body weight, in PBS buffer) and physiological saline (DPBS) as a negative control. After 21 days, treatment with ß-SnWO4 resulted in a clearly inhibited growth of the primary tumor (all tumor volumes below 3 cm(3)) as compared to the doxorubicin and DPBS control groups (volumes up to 6 cm(3)). Histological evaluations of lymph nodes and lungs as well as the volume of ipsilateral lymph nodes show a remarkable antimetastatic effect being similar to chemotherapeutic doxorubicin but-according to blood counts-at significantly reduced side effects. On the basis of low material complexity, high cytotoxicity under blue-light LED illumination at low dark and long-term toxicity, ß-SnWO4 can be an interesting addition to PDT and the treatment of near-surface tumors, including skin cancer, esophageal/gastric/colon tumors as well as certain types of breast cancer.

Mitophagy induced by nanoparticle-peptide conjugates enabling an alternative intracellular trafficking route.

The intracellular behaviors of nanoparticles are fundamentally important for the evaluation of their biosafety and the designs of nano carrier-assisted drug delivery with high therapeutic efficacy. It is still in a great need to discover how functionalized nanoparticles are transported inside the cells, for instance, in a complicated fashion of translocation between different types of cell organelles. Here we report a new understanding of the interactions between nanoparticles and cells by the development of polyoxometalates nanoparticle-peptide conjugates and investigation of their intracellular trafficking behaviors. The as-prepared nanoparticles are featured with a unique combination of fluorescence and high contrast for synchrotron X-ray-based imaging. Functional surface modification with peptides facilitates effective delivery of the nanoparticles onto the target organelle (mitochondria) and subsequent intracellular trafficking in a dynamic mode. Interestingly, our experimental results have revealed that autophagy of mitochondria (mitophagy) can be induced by NP-peptide as a cellular response for recycling the damaged organelles, through molecular mediation associated with the change of mitochondrial membrane potential. The biological effects induced by NP-peptide reciprocally affect the distribution patterns and fates of nanoparticles in the cell metabolism by providing an alternative route of intracellular trafficking. The new understanding of the mutual activities between nanoparticles and cells will enrich our approaches in the development of nanobiotechnology and nano-medicine for disease treatments.

An update to the toxicological profile for water-soluble and sparingly soluble tungsten substances.

Tungsten is a relatively rare metal with numerous applications, most notably in machine tools, catalysts, and superalloys. In 2003, tungsten was nominated for study under the National Toxicology Program, and in 2011, it was nominated for human health assessment under the US Environmental Protection Agency's (EPA) Integrated Risk Information System. In 2005, the Agency for Toxic Substances and Disease Registry (ATSDR) issued a toxicological profile for tungsten, identifying several data gaps in the hazard assessment of tungsten. By filling the data gaps identified by the ATSDR, this review serves as an update to the toxicological profile for tungsten and tungsten substances. A PubMed literature search was conducted to identify reports published during the period 2004-2014, in order to gather relevant information related to tungsten toxicity. Additional information was also obtained directly from unpublished studies from within the tungsten industry. A systematic approach to evaluate the quality of data was conducted according to published criteria. This comprehensive review has gathered new toxicokinetic information and summarizes the details of acute and repeated-exposure studies that include reproductive, developmental, neurotoxicological, and immunotoxicological endpoints. Such new evidence involves several relevant studies that must be considered when regulators estimate and propose a tungsten reference or concentration dose.

Studies on some fish parasites of public health importance in the southern area of Saudi Arabia / Estudos sobre alguns parasitas de peixes com importância para a saúde pública na região sul da Arábia Saudita

The present study was the first attempt to survey the diversity of fish zoonotic parasites in the southern region of Saudi Arabia, particularly the Najran area, from October 2012 to October 2013. Approximately 163 fish representing seven species (two of freshwater fish and five of marine fish) were examined for fish-borne trematode metacercariae using the compression technique, and for zoonotic nematode larvae. Adult flukes were obtained from cats experimentally infected with the metacercariae on day 25 post-infection The prevalence of each parasite species was recorded. The parasites found belonged to two taxa: Digenea (Heterophyes heterophyes and Haplorchis pumilio) in muscle tissue; and nematodes (larvae of Capillaria sp.) in the digestive tract. The morphological characteristics of the fish-borne trematode metacercariae and their experimentally obtained adults were described. This is the first report of these parasites in fish in Saudi Arabia. Moreover, Myripristis murdjan presented higher prevalence of Capillaria sp. infection (22.7%), while Haplorchis pumilio was the dominant metacercarial species (7.9%). Although the number of documented cases continues to increase, the overall risk of human infection is slight. The increasing exploitation of the marine environment by humans and the tendency to reduce cooking times when preparing seafood products both increase the chances of becoming infected with these parasites. Furthermore, our results indicate that certain fish production systems are at risk of presenting fish zoonotic parasites, and that control approaches will benefit from understanding these risk factors.

O presente estudo representa a primeira tentativa para investigar a diversidade dos parasitas zoonóticos em peixes na Região Sul da Arábia Saudita, em particular na área de Najran, de outubro de 2012 a outubro de 2013. Aproximadamente, 163 peixes representando sete espécies (duas de água doce e cinco marinhas) foram examinados para as metacercária, dos trematódeos de peixes, usando-se a técnica de compressão e para as larvas de nematoides. Os trematódeos adultos foram obtidos em gatos experimentalmente infectados com metacercárias no 25° dia após a infecção. A prevalência de cada espécie parasita foi registrada. Os parasitas encontrados pertenciam a dois taxa: Digenea (Heterophyes heterophyes e Haplorchis pumilio) no tecido muscular; e nematoides (larvas de Capillaria sp.) no trato digestivo. As características morfológicas das metacercárias dos trematódeos de peixes e dos adultos experimentalmente obtidos são descritas. Esse é o primeiro relato desses parasitas em peixes da Arábia Saudita. Além desses, Myripristis murdjan apresentou alta prevalência de infecção por Capillaria sp. (22,7%), enquanto Haplorchis pumilio foi a espécie de metacercárias dominante (7,9%). Embora o número de casos documentados continue a aumentar, o risco global de infecção humana é pequeno. A exploração crescente do ambiente marinho pelos seres humanos e a tendência de redução do processo de cozimento no preparo de alimentos oriundos do mar aumentam as chances de infecção por esses parasitas. Os resultados deste estudo também indicam que certos sistemas de produção de pescados estão em risco de apresentar parasitas zoonóticos, e que o seu controle trará benefícios na compreensão destes fatores de risco.

Pharmacokinetics of anti-HBV polyoxometalate in rats.

Polyoxometalates are non-nucleoside analogs that have been proven to exhibit broad-spectrum antiviral activity. In particular, Cs2K4Na[SiW9Nb3O40].H2O 1 shows low toxicity and high activity against HBV. The preclinical pharmacokinetics of Compound 1 in rats were characterized by establishing and applying inductively coupled plasma-mass spectrometry method to determine the concentration of W in plasma, urine, feces, bile and organ samples. The quantitative ICP-MS method demonstrated good sensitivity and application in the pharmacokinetics study of polyoxometalates. The pharmacokinetic behavior of Compound 1 after intravenous or oral administration fit a two-compartment model. Tmax ranges from 0.1 h to 3 h and the T1/2 of Compound 1 is between 20 h and 30 h. The absolute bioavailability of Compound 1 at 45, 180 and 720 mg/kg groups were 23.68%, 14.67% and 11.93%, respectively. The rates of plasma protein binding of Compound 1 at 9, 18 and 36 mg/ml of Compound 1 are 62.13±9.41%, 71.20±24.98% and 49.00±25.59%, respectively. Compound 1 was widely distributed throughout the body, and high levels of compound 1 were found in the kidney and liver. The level of Compound 1 in excretion was lower: 30% for urine, 0.28% for feces and 0.42% for bile, respectively. For elaborate pharmacokinetic characteristics to be fully understood, the metabolism of Compound 1 needs to be studied further.

Synthesis, characterization and bioimaging of fluorescent labeled polyoxometalates.

A fluorescent labeled Wells-Dawson type POM ({P2W17O61Fluo}) was newly synthesized and characterized by a wide range of analytical methods. {P2W17O61Fluo} was functionalized with fluorescein amine through a stable amide bond, and its long time stability was verified by UV/vis spectroscopic techniques at physiologically relevant pH values. No significant impact on the cell viability or morphology of HeLa cells was observed for POM concentrations up to 100 µg mL(-1). Cellular uptake of fluorescent {P2W17O61Fluo} was monitored by confocal laser scanning microscopy. POM uptake occurs mainly after prolonged incubation times of 24 h resulting in different intracellular patterns, i.e. randomly distributed over the entire cytoplasm, or aggregated in larger clusters. This direct monitoring strategy for the interaction of POMs with cells opens up new pathways for elucidating their unknown mode of action on the way to POM-based drug development.

Tissue distribution of tungsten in mice following oral exposure to sodium tungstate.

Heavy metal tungsten alloys have replaced lead and depleted uranium in many munitions applications, due to public perception of these elements as environmentally unsafe. Tungsten materials left in the environment may become bioaccessible as tungstate, which might lead to population exposure through water and soil contamination. Although tungsten had been considered a relatively inert and toxicologically safe material, recent research findings have raised concerns about possible deleterious health effects after acute and chronic exposure to this metal. This investigation describes tissue distribution of tungsten in mice following oral exposure to sodium tungstate. Twenty-four 6-9 weeks-old C57BL/6 laboratory mice were exposed to different oral doses of sodium tungstate (0, 62.5, 125, and 200 mg/kg/d) for 28 days, and after one day, six organs were harvested for trace element analysis with inductively coupled plasma mass spectrometry (ICP-MS). Kidney, liver, colon, bone, brain, and spleen were analyzed by sector-field high-resolution ICP-MS. The results showed increasing tungsten levels in all organs with increased dose of exposure, with the highest concentration found in the bones and the lowest concentration found in brain tissue. Gender differences were noticed only in the spleen (higher concentration of tungsten in female animals), and increasing tungsten levels in this organ were correlated with increased iron levels, something that was not observed for any other organ or either of the two other metals analyzed (nickel and cobalt). These findings confirmed most of what has been published on tungsten tissue distribution; they also showed that the brain is relatively protected from oral exposure. Further studies are necessary to clarify the findings in splenic tissue, focusing on possible immunological effects of tungsten exposure.

Pharmacokinetics of radiolabeled tungsten ((188)W) in male Sprague-Dawley rats following acute sodium tungstate inhalation.

Aerosol cloud formation may occur when certain tungsten munitions strike hard targets, placing military personnel at increased risk of exposure. Although the pharmacokinetics of various forms of tungsten have been studied in animals following intravenous and oral administration, tungsten disposition following inhalation remains incompletely characterized. The objective of this study was to evaluate the pharmacokinetics of inhaled tungstate (WO(4)) in rats. Male, 16-wk-old, CD rats (n = 7 rats/time point) underwent a single, 90-min, nose-only exposure to an aerosol (mass median aerodynamic diameter [MMAD] 1.50 mum ) containing 256 mg W/m(3) as radiolabeled sodium tungstate (Na(2)(188)WO(4)). (188)W tissue concentrations were determined at 0, 1, 3, 7, and 21 days postexposure by gamma spectrometry. The thyroid and urine had the highest (188)W levels postexposure, and urinary excretion was the primary route of (188)W elimination. The pharmacokinetics of tungsten in most tissues was best described with a two-compartment pharmacokinetic model with initial phase half-lives of approximately 4 to 6 h and a longer terminal phase with half-lives of approximately 6 to 67 days. The kidney, adrenal, spleen, femur, lymph nodes, and brain continued to accumulate small amounts of tungsten as reflected by tissue:blood activity ratios that increased throughout the 21-day period. At day 21 all tissues except the thyroid, urine, lung, femur, and spleen had only trace levels of (188)W. Data from this study can be used for development and refinement of pharmacokinetic models for tungsten inhalation exposure in environmental and occupational settings.

Acute sodium tungstate inhalation is associated with minimal olfactory transport of tungsten (188W) to the rat brain.

Olfactory transport of represents an important mechanism for direct delivery of certain metals to the central nervous system (CNS). The objective of this study was to determine whether inhaled tungsten (W) undergoes olfactory uptake and transport to the rat brain. Male, 16-week-old, Sprague-Dawley rats underwent a single, 90-min, nose-only exposure to a Na(2)(188)WO(4) aerosol (256 mg W/m(3)). Rats had the right nostril plugged to prevent nasal deposition of (188)W on the occluded side. The left and right sides of the nose and brain, including the olfactory pathway and striatum, were sampled at 0, 1, 3, 7, and 21 days post-exposure. Gamma spectrometry (n=7 rats/time point) was used to compare the levels of (188)W found on the left and right sides of the nose and brain and blood to determine the contribution of olfactory uptake to brain (188)W levels. Respiratory and olfactory epithelial samples from the side with the occluded nostril had significantly lower end-of-exposure (188)W levels confirming the occlusion procedure. Olfactory bulb, olfactory tract/tubercle, striatum, cerebellum, rest of brain (188)W levels paralleled blood (188)W concentrations at approximately 2-3% of measured blood levels. Brain (188)W concentrations were highest immediately following exposure, and returned to near background concentrations within 3 days. A statistically significant difference in olfactory bulb (188)W concentration was seen at 3 days post-exposure. At this time, (188)W concentrations in the olfactory bulb from the side ipsilateral to the unoccluded nostril were approximately 4-fold higher than those seen in the contralateral olfactory bulb. Our data suggest that the concentration of (188)W in the olfactory bulb remained low throughout the experiment, i.e., approximately 1-3% of the amount of tungsten seen in the olfactory epithelium suggesting that olfactory transport plays a minimal role in delivering tungsten to the rat brain.

Comparison between exhaled breath condensate analysis as a marker for cobalt and tungsten exposure and biomonitoring in workers of a hard metal alloy processing plant.

OBJECTIVE: Cobalt (Co), Tungsten (W) and Tungsten Carbides (WC) are major constituents of hard metal alloys. Whereas little is known about potential health hazards due to tungsten carbide exposure, occupational exposure to cobalt has been shown to induce a variety of respiratory diseases. Since the concentration of a potentially hazardous substance in the target organ is the most meaningful risk indicator in occupational medicine, the detection of hard metals in exhaled breath condensate (EBC) has been proposed to be a valuable instrument. The present study examines the correlation of Co and W concentrations in EBC and urine with one another and various spirometrical and clinical parameters to scrutinize this potential. METHODS: A total of 62 subjects (90.3% males, age 40.6 +/- 9.2 years) were recruited from a hard metal processing plant in Germany. Examinations included the airborne workplace exposure, a complete spirometry, measurements of Co and W concentrations in EBC and urine with high resolution inductive coupled plasma mass spectrometry (HR ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS). RESULTS: Air concentrations ranged between 0.0019 mg/m(3) and 0.074 mg/m(3) for Co and 0.012 mg/m(3) and 0.021 mg/m(3) for W. Median urine concentrations and interquartile ranges of the exposed subjects ranged from 0.81 (0.0-1.46) microg/l for Co and 30.5 (14.5-57.7) microg/l for W. Median breath condensate metal concentrations and interquartile ranges ranged from 8.4 (5.0-13.9) microg/l for Co and 8.8 (4.4-18.5) microg/l for W. Urine concentrations of Co and W were closely related to the airborne workplace exposure that had been assessed by air monitoring. EBC concentrations of Co and W showed no correlations to urinary W and Co concentrations and the ambient monitoring results of the individual workplace, respectively. Cobalt EBC concentration was elevated in subjects who reported to have suffered from respiratory disease; both Co and W concentrations in EBC, however, decreased with increasing spirometrical signs of obstruction. CONCLUSION: According to our study, urinary concentrations of Co and W seem to be more reliable indicators of current workplace exposure than EBC concentrations. As far as new methods and exposure matrices for valid concentration measurements in respiratory organs and possible hazardous effects--especially of cobalt--in the lung are concerned, the present results are less clear-cut, and further research is required.

Validation of an inductively coupled plasma-mass spectrometry method to quantify tungsten in human plasma. Determination of percentage binding to plasma proteins.

BACKGROUND: The aim of this paper was to validate an inductively coupled plasma-mass spectrometry (ICP-MS) method to quantify tungsten in human plasma and to study its percentage binding to plasma proteins. METHODS: This method was validated with respect to accuracy, precision, selectivity and limits of quantification and of detection according to Good Laboratory Practice Guidelines. Calibration curves were obtained in the range 10-500 ng/ml. The extent of plasma protein binding was determined by ultrafiltration in the range 40-2000 ng/ml. RESULTS: A significant matrix effect was observed. The linearity of this method was statistically proven. Precision ranged from 0.76% to 6.49%, and accuracy from 97% to 102%. The lower limit of quantification (LLOQ) was 10 ng/ml. The mean percentage of unbound fraction was 89%. CONCLUSIONS: The results obtained indicate that the method described fulfills the accuracy and precision requirements necessary to carry out pharmacokinetic studies in man.

Influence of food and diabetes on pharmacokinetics of sodium tungstate in rat.

In this paper, the influence of food and diabetes on the pharmacokinetics of sodium tungstate in rat was investigated. The compound was administered intravenously (9 mg/kg) and orally in the form of solution (36 mg/kg). An empirical Bayes methodology was used to compute individual pharmacokinetic parameters. Sodium tungstate followed first-order kinetics, and plasma concentration versus time data were described by a two-compartment model. A significant relationship was found between the bioavailability and the status of the animals. Total plasma clearance and elimination half-life averaged 3.1 ml/min/kg and 1.6 h, respectively. Food had some effects on the extent of sodium tungstate absorption. After oral administration, the bioavailability (0.67 versus 0.85), C(max) (6.10 versus 15.2 microg/ml) and AUC (70.7 versus 105 mgh/l) were 20, 60 and 32% lower in fed than in fasted rats, respectively. The presence of cellulose and sulphate anions in rat chow could partially explain the fed state-associated reduction of tungstate bioavailability. In streptozotocin-induced diabetic fed rats, a 25% decrease occurred in AUC and F, and a 14% increase occurred in the elimination rate constant compared with healthy fed rats. These changes could be explain on the one hand, by the increase of liquid consumption and food intake, and on the other hand, by a gastroparesis in the early diabetic rats.

An application of population kinetics analysis to estimate pharmacokinetic parameters of sodium tungstate after multiple-dose during preclinical studies in rats.

The purpose of this study was to use a population approach in the preclinical development program of sodium tungstate in the rat in order i) to compute individual pharmacokinetic parameters of this compound after repeated oral administrations, until the 4-week toxicology study, using an empirical Bayes methodology; and ii) to study the influence of the administered dose, of the gender and of the duration of treatment on the pharmacokinetic parameters. Four studies were used representing a mixture of single intravenous administration and multiple oral administrations. The treatment duration ranged from 7 to 28 days. Intravenous dose was 9 mg/kg; three different oral doses were tested, 50, 100 and 200 mg/kg/day. Plasma concentration profiles versus time were compatible with a two-compartment model. A significant gender effect was found on bioavailability. The duration of treatment and the administered dose did not significantly explain part of the interindividual variability of pharmacokinetic parameters. The absorption of tungsten was rapid (1-3 hr). Total plasma clearance and elimination half-life averaged 2.8 ml/min/kg and 3.04 hr in males, and 3 ml/min/kg and 2.74 hr in females. The bioavailability was on an average 70%; being significantly higher in females than in males (0.78 versus 0.61). This compartmental approach should be considered as complementary to the usual non-compartmental approach used for analysis of preclinical data and should be a valuable tool to characterise the pharacokinetic/pharmacodynamic behaviour of a drug.

Estimation of pharmacokinetic parameters of sodium tungstate after multiple-dose during preclinical studies in beagle dogs.

In this paper, an empirical Bayes methodology was used to determine the pharmacokinetic profile of sodium tungstate in beagle dogs after multiple oral dosing using the P-PHARM computer program. The population estimation algorithm used in P-PHARM is an EM-type procedure. Sodium tungstate was administered orally, three times a day, (i) for 11 days (21 and 42 mg/kg per day) to 18 dogs (nine males and nine females) and (ii) for 13 weeks (15, 30 and 60 mg/kg per day) to 28 dogs (14 males, 14 females). Six other dogs received the compound intravenously (25 and 50 mg/kg). Plasma concentration profiles versus time were compatible with a two-compartment model and first-order kinetics. After oral administration, F (0.61+/-0.086 vs. 0.48+/-0.093), and normalized (to a 7-mg/kg dose of sodium tungstate) AUC (54+/-8.4 vs. 41.2+/-8.5 mg/l x h), C(max) (10.6+/-0.49 vs. 8.5+/-0.57 microg/ml) and C(min) (3.04+/-0.23 vs. 2.04+/-0.22 microg/ml), were higher in male than in female dogs. However, the introduction of the gender in the final model did not contribute statistically to an improvement of the fit of the population pharmacokinetic model. In males, t(1/2) elimination averaged 3.1+/-0.56 vs. 2.6+/-0.18 h in females. The duration of treatment did not modify statistically the pharmacokinetic parameters. After repeated multiple oral administration of 15-60 mg/kg per day of sodium tungstate, tungsten plasma concentrations increased in proportion to dose. No dose-dependent changes in pharmacokinetic parameters occurred.

Exposure assessment in the hard metal manufacturing industry with special regard to tungsten and its compounds.

OBJECTIVES: To assess the exposure to tungsten, cobalt, and nickel in a plant producing hard metals. The main components of hard metals are tungsten carbide and cobalt metal. According to recent studies, these two components may be responsible for both fibrogenic and carcinogenic effects. METHODS: 87 workers were investigated (86 male, one female) with a median age of 42 (range 22-58) and a mean duration of exposure of 13 years (range 1-27 years). Stationary and personal air sampling, and biological monitoring were carried out. RESULTS: Ambient monitoring yielded maximum tungsten concentrations of 417 microg/m3 in the production of heavy alloys. A maximum cobalt concentration of 343 microg/m3 and a maximum nickel concentration of 30 microg/m3 were found at the sintering workshop. The highest urinary cobalt concentrations were found in the powder processing department. The mean concentration was 28.5 microg/g creatinine and the maximum value was 228 microg/g creatinine. The maximum nickel concentration in urine of 6.3 microg/g creatinine was detected in the department producing heavy alloys. The highest tungsten concentrations excreted in urine were found in grinders and had a mean value of 94.4 microg/g creatinine and a maximum of 169 microg/g creatinine. Due to the different solubility and bioavailability of the substance, there was no correlation between the tungsten concentrations in air and urine on a group basis. CONCLUSIONS: Despite its low solubility, tungsten carbide is bioavailable. The different bioavailability of tungsten metal and tungsten compounds has to be considered in the interpretation of ambient and biological monitoring data in the hard metal producing industry. The bioavailability increases in the order: tungsten metal, tungsten carbide, tungstenate. Only if both monitoring strategies are considered in combination can a valid and effective definition of high risk groups be derived.

Tungstate Uptake by a highly specific ABC transporter in Eubacterium acidaminophilum.

The Gram-positive anaerobe Eubacterium acidaminophilum contains at least two tungsten-dependent enzymes: viologen-dependent formate dehydrogenase and aldehyde dehydrogenase. (185)W-Labeled tungstate was taken up by this organism with a maximum rate of 0.53 pmol min(-)1 mg(-)1 of protein at 36 degrees C. The uptake was not affected by equimolar amounts of molybdate. The genes tupABC coding for an ABC transporter specific for tungstate were cloned in the downstream region of genes encoding a tungsten-containing formate dehydrogenase. The substrate-binding protein, TupA, of this putative transporter was overexpressed in Escherichia coli, and its binding properties toward oxyanions were determined by a native polyacrylamide gel retardation assay. Only tungstate induced a shift of TupA mobility, suggesting that only this anion was specifically bound by TupA. If molybdate and sulfate were added in high molar excess (>1000-fold), they were also slightly bound by TupA. The K(d) value for tungstate was determined to be 0.5 microm. The genes encoding the tungstate-specific ABC transporter exhibited highest similarities to putative transporters from Methanobacterium thermoautotrophicum, Haloferax volcanii, Vibrio cholerae, and Campylobacter jejuni. These five transporters represent a separate phylogenetic group of oxyanion ABC transporters as evident from analysis of the deduced amino acid sequences of the binding proteins. Downstream of the tupABC genes, the genes moeA, moeA-1, moaA, and a truncated moaC have been identified by sequence comparison of the deduced amino acid sequences. They should participate in the biosynthesis of the pterin cofactor that is present in molybdenum- and tungsten-containing enzymes except nitrogenase.

Pharmacokinetics of sodium tungstate in rat and dog: a population approach.

Sodium tungstate has been found to correct hyperglycemia in insulin- and noninsulin-dependent models of diabetes when administered in drinking fluid with a low degree of toxicity; thus, it provides a potential treatment for diabetes. In the present report, pharmacokinetic studies with sodium tungstate were carried out in the Sprague-Dawley rat and beagle dog. This drug was administered either i.v. (8.97 mg/kg in rat; 25 and 50 mg/kg in dog) or orally in the form of solution (35.9 and 107.7 mg/kg in rat; 25 and 50 mg/kg in dog). Tungsten was quantified using an inductively coupled plasma method. Pharmacokinetic parameters were estimated using a population approach. Sodium tungstate followed first order kinetics, and plasma concentration-versus-time data were adequately described by a two-compartment model. In rat, bioavailability was high (92%), whereas it was lower in dog (approximately 65%). The total volume of distribution expressed by unit of body weight was much higher when the animal was smaller (0.46 l/kg in rat versus 0.23 l/kg in dog). The total body clearance normalized by weight, 0.19 l/h/kg in rat versus 0.043 l/h/kg in dog, changed as for the volume of distribution. The elimination half-life was two times higher in dog (approximately 4 h) than in rat (approximately 1.7 h). In the range of 35.9 to 107.7 mg/kg after oral administration in rat and 25 to 50 mg/kg after oral and i.v. administration in dog, tungsten plasma concentrations increased in proportion to dose.