Intestinal Transport of ²⁰³Hg-Labeled Methyl Mercury Chloride

Abstract

Mercury transport pathways through the gastrointestinal tract were investigated to explain preferential inorganic mercury excretion in feces after exposure to methyl mercury salts. Mercury is excreted in bile predominantly as methyl mercury cysteine. Protein-complexed methyl mercury and protein-bound inorganic Hg are found less extensively. Methyl mercury cysteine is rapidly reabsorbed, not adding significantly to fecal Hg. Protein-bound inorganic Hg is not reabsorbed and comprises about 15% total fecal Hg the first days after methyl mercury chloride injection. A corresponding fecal Hg amount derives from protein-bound methyl mercury from bile. Intestinal cell shedding is the main fecal Hg source. These cells, however, contain less than 5% inorganic Hg, compared to about 50% in feces. Methyl mercury bound to structural proteins in these cells releases inorganic Hg, probably by lower-intestinal microbiological action.