Internal dose of vanadium in rats following repeated exposure to vanadyl sulfate and sodium orthovanadate via drinking water.

Vanadium is a ubiquitous environmental contaminant that exists in multiple oxidation states. Humans are exposed to vanadyl (V4+) and vanadate (V5+) from dietary supplements, food, and drinking water and hence there is a concern for adverse human health. The current investigation is aimed at identifying vanadium oxidation states in vitro and in vivo and internal concentrations following exposure of rats to vanadyl sulfate (V4+) or sodium metavanadate (V5+) via drinking water for 14 d. Investigations in simulated gastric and intestinal fluids showed that V4+ was stable in gastric fluid while V5+ was stable in intestinal fluid. Analysis of rodent plasma showed that the only vanadium present was V4+, regardless of the exposed compound suggesting conversion of V5+ to V4+ in vivo and/or instability of V5+ species in biological matrices. Plasma, blood, and liver concentrations of total vanadium, after normalizing for vanadium dose consumed, were higher in male and female rats following exposure to V5+ than to V4+. Following exposure to either V4+ or V5+, the total vanadium concentration in plasma was 2- to 3-fold higher than in blood suggesting plasma as a better matrix than blood for measuring vanadium in future work. Liver to blood ratios were 4-7 demonstrating significant tissue retention following exposure to both compounds. In conclusion, these data point to potential differences in absorption and disposition properties of V4+ and V5+ salts and may explain the higher sensitivity in rats following drinking water exposure to V5+ than V4+ and highlights the importance of internal dose determination in toxicology studies.

Finding the bad actor: Challenges in identifying toxic constituents in botanical dietary supplements.

Botanical-derived dietary supplements have widespread use in the general population. The complex and variable nature of botanical ingredients and reports of adverse responses have led to concern for negative human health impacts following consumption of these products. Toxicity testing of the vast number of available products, formulations, and combinations is not feasible due to the time and resource intensive nature of comprehensive testing. Methods are needed to assess the safety of a large number of products via more efficient frameworks. Identification of toxicologically-active constituents is one approach being used, with many advantages toward product regulation. Bioassay-guided fractionation (BGF) is the leading approach used to identify biologically-active constituents. Most BGF studies with botanicals focus on identifying pharmacologically-active constituents for drug discovery or botanical efficacy research. Here, we explore BGF in a toxicological context, drawing from both efficacy and poisonous plant research. Limitations of BGF, including loss of mixture activity and bias toward abundant constituents, and recent advancements in the field (e.g., biochemometrics) are discussed from a toxicological perspective. Identification of active constituents will allow better monitoring of market products for known toxicologically-active constituents, as well as surveying human exposure, two important steps to ensuring the safety of botanical dietary supplements.

14-Day Toxicity Studies of Tetravalent and Pentavalent Vanadium Compounds in Harlan Sprague Dawley Rats and B6C3F1/N Mice via Drinking Water Exposure.

BACKGROUND: The National Toxicology Program (NTP) performed short-term toxicity studies of tetra- and pentavalent vanadium compounds, vanadyl sulfate and sodium metavanadate, respectively. Due to widespread human exposure and a lack of chronic toxicity data, there is concern for human health following oral exposure to soluble vanadium compounds. OBJECTIVES: To compare the potency and toxicological profile of vanadyl sulfate and sodium metavanadate using a short-term in vivo toxicity assay. METHODS: Adult male and female Harlan Sprague Dawley (HSD) rats and B6C3F1/N mice, 5 per group, were exposed to vanadyl sulfate or sodium metavanadate, via drinking water, at concentrations of 0, 125, 250, 500, 1000 or 2000 mg/L for 14 days. Water consumption, body weights and clinical observations were recorded throughout the study; organ weights were collected at study termination. RESULTS: Lower water consumption, up to -80% at 2000 mg/L, was observed at most exposure concentrations for animals exposed to either vanadyl sulfate or sodium metavanadate and was accompanied by decreased body weights at the highest concentrations for both compounds. Animals in the 1000 and 2000 mg/L sodium metavanadate groups were removed early due to overt toxicity. Thinness was observed in high-dose animals exposed to either compound, while lethargy and abnormal gait were only observed in vanadate-exposed animals. CONCLUSIONS: Based on clinical observations and overt toxicity, sodium metavanadate appears to be more toxic than vanadyl sulfate. Differential toxicity cannot be explained by differences in total vanadium intake, based on water consumption, and may be due to differences in disposition or mechanism of toxicity.