Reduction and methylation of sodium arsenate in the rat.

After a single oral dose of sodium [74As] arsenate to male Wistar rats, arsenic was rapidly absorbed and accumulated in the blood and to a lesser extent in the liver, kidneys, lungs and spleen. Within 1 h of dosing, arsenic was present in the blood, liver and spleen predominantly in the methylated forms (methylarsonic acid and dimethylarsinic acid), whereas in the lung and kidneys, approximately 50% was in the inorganic form. Intravenous injection of sodium [74As] arsenate resulted in a pattern of arsenic species in the blood and kidneys similar to that seen after oral administration, suggesting that the gut flora does not contribute significantly to biotransformation of arsenic in vivo. Analysis of the forms of arsenic in portal blood after administration of arsenate via the small intestine revealed a rapid reduction of arsenate to arsenite, followed by linear rates of production of methylarsonic acid and dimethylarsinic acid.