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TISSUE DOSIMETRY, METABOLISM AND EXCRETION OF PENTAVALENT AND TRIVALENT MONOMETHYLATED ARSENIC IN MICE AFTER ORAL ADMINISTRATION
Citation:
HUGHES, MICHAEL F., V. DEVESA I PEREZ, B. ADAIR, M. STYBLO, E. M. KENYON, AND D. J. THOMAS. TISSUE DOSIMETRY, METABOLISM AND EXCRETION OF PENTAVALENT AND TRIVALENT MONOMETHYLATED ARSENIC IN MICE AFTER ORAL ADMINISTRATION. TOXICOLOGY AND APPLIED PHARMACOLOGY. Elsevier Science Ltd, New York, NY, 208:186-197, (2005).
Description:
Exposure to monomethylarsonic acid (MMA(V)) and monomethylarsonous acid (MMA(III)) can result from their formation as metabolites of inorganic arsenic and by the use of the sodium salts of MMA(V) as herbicides. This study compared the disposition of MMA(V) and MMA(III) in adult female B6C3F1 mice. Mice were gavaged po with MMA(V), either unlabeled or labeled with 14C at two dose levels (0.4 or 40 mg As/kg). Other mice were dosed po with unlabeled MMA(III) at one dose level (0.4 mg As/kg). Mice were housed in metabolism cages for collection of excreta and sacrificed serially over 24 h for collection of tissues. MMA(V)-derived radioactivity was rapidly absorbed, distributed and excreted. By 8 h post-exposure, 80% of both doses of MMA(V) were eliminated in urine and feces. Absorption of MMA(V) was dose-dependent; that is, there was less than a 100-fold difference between the two dose levels in the area under the curves for the concentration-time profiles of arsenic in blood and major organs. In addition, urinary excretion of MMA(V)-derived radioactivity in the low dose group was significantly greater (p < 0.05) than in the high dose group. Conversely, fecal excretion of MMA(V)-derived radioactivity was significantly greater (p < 0.05) in the high dose group than in the low dose group. Speciation of arsenic by hydride generation-atomic absorption spectrometry in urine and tissues of mice administered MMA(V) or MMA(III) found that methylation of MMAV) was limited while the methylation of MMA(III) was extensive. Less than 10% of the dose excreted in urine of MMA(V)-treated mice was in the form of methylated products, whereas it was greater than 90% for MMA(III)-treated mice. No more than 25% of the distribution of arsenic in tissues was in the form of methylated products of MMA(V)-treated mice, whereas it was 75% or greater in tissues of MMA(III)-treated mice. Based on urinary analysis, administered dose of MMA(V) did not affect the level of its metabolites excreted. In the tested range, dose affects the absorption and route of excretion of MMA(V) but not its metabolism.