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Lowered dietary phosphate increases oral bioavailability of arsenate in mice
Citation:
Lee, G., B. C. EDWARDS, K. Herbin-Davis, M. F. HUGHES, AND D. J. THOMAS. Lowered dietary phosphate increases oral bioavailability of arsenate in mice. Presented at Society of Toxicology (SOT) Annual Meeting, San Francisco, CA, March 11 - 15, 2012.
Impact/Purpose:
This abstract reports that lowered dietary phosphorus concentration increases the bioavailability of arsenic in adult female mice that received a powdered purified rodent diet that is amended with arsenate. Increased bioavailability of arsenic in mice receiving a low phosphorus diet likely reflects sharing of transporters which mediate uptake of the oxyanions arsenate and phosphate across cell membranes.
Description:
Arsenate (iAsv), an inorganic oxyanionic species, has physicochemical properties similar to inorganic phosphate (iP). There is evidence that iAsv competes with iP for transmembrane carriers that mediate iP uptake. Thus, it is possible that altered dietary intake of iP could modify the bioavailability of ingested iAsv. In a mouse bioavailability assay, we have examined the effect of dietary phosphorus (P) content on bioavailability of iAsv. Adult female C57BL/6 mice received a powdered AIN-93G rodent diet amended by the addition of iAsv ('" 5ppm) that contained either the normal concentration of P (NP, 0.3% P) or reduced concentration of P (LP, 0.15%). Mice had free access to either diet and drinking water throughout a 9-day exposure period. Food and water intake were monitored and urine and feces collected for As determination by instrumental neutron activation analysis. Under these conditions, neither altered dietary P nor iAsv amendment of diet significantly affected food and water consumption or weight gain during exposure. Compared with NP diet, ingestion of LP diet significantly lowered (P < 0.05) concentrations of iP in urine and serum. The absolute bioavailability of As in mice ingesting the NP diet amended with iAsv was significantly lower than the absolute bioavailability of As in mice ingesting the LP diet amended with iAsv (P < 0.001 by Mann-Whitney rank sum test). Increased bioavailability of dietary As in mice consuming LP diet suggests that physiological processes affecting P homeostasis that are upregulated during ingestion of LP diet promote the absorption and retention of As. Hence, P nutriture could be an important determinant of the bioavailability in individuals exposed to iAsv. (This abstract does not reflect the policies of the U.S. E.P.A.).