EFFECTS OF DIET ON MERCURY METABOLISM AND EXCRETION IN MICE GIVEN METHYLMERCURY - ROLE OF GUT FLORA

Mice fed either a pelleted rodent diet, evaporated milk or a synthetic diet (high protein, low fat) exhibited different rates of whole body Hs elimination and fecal Hs excretion after exposure (per os) to methylmercuric chloride. The percentage of the total Hs body burden present as mercuric mercury was highest (35.3%) in mice fed the synthetic diet (which had the highest rate of Hs elimination) and lowest (6.6%) in the animals having the lowest Hs elimination rate (milk-fed mice). Mice fed the synthetic diet had lower Hs concentrations and had a higher proportion of mercuric mercury in their tissues than the mice from the other dietary groups. Treatment of the mice with antibiotics throughout the experimental period to suppress the gut flora reduced fecal Hs excretion and the dietary differences in whole body retention of Hs. Tissue Hs concentrations and proportion of organic Hs in feces, cecal contents, liver and kidneys were increased by antibiotic treatment of mice fed the pelleted or synthetic diets. These results are consistent with the theory that demethylation of methylmercury by intestinal microflora is a major factor determining the excretion rate of Hs.