LIBERATION AND ANALYSIS OF PROTEIN-BOUND ARSENICALS

Protein-bound arsenicals were liberated from binding sites on liver cy tosolic proteins by exposure to 0.1 M CuCl at pH 1. This method releas ed greater than 90% of the arsenicals associated with biological matri ces. Ultrafiltrates of CuCl-treated cytosols were subjected to thin-la yer chromatography to speciate and quantify inorganic and methylated a rsenicals. For rat liver cytosol in an in vitro methylation assay and for liver and kidney cytosols from arsenite-treated mice, most inorgan ic arsenic was protein bound. Appreciable fractions of the organoarsen ical metabolites present in these cytosols were also protein bound. Th erefore, CuCl treatment of cytosols releases protein-bound arsenicals, permitting more accurate estimates of the pattern and extent of arsen ic methylation in vitro and in vivo.