Effects of Diet on Mercury Metabolism and Excretion in Mice Given Methylmercury: Role of Gut Flora

Abstract

Mice fed either (1) a pelleted rodent diet, (2) evaporated milk, or (3) a synthetic diet (high protein, low fat) exhibited different rates of whole body mercury elimination and fecal mercury excretion after exposure (per os) to methylmercuric chloride. The percentage of the total mercury body burden present as mercuric mercury was highest (35.3%) in mice fed the synthetic diet (which had the highest rate of mercury elimination) and lowest (6.6%) in the animals having the lowest mercury elimination rate (milk-fed mice). Mice fed the synthetic diet had lower mercury 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 mercury excretion and the dietary differences in whole body retention of mercury. Tissue mercury concentrations and proportion of organic mercury 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 mercury.

Effects of breast feeding on neuropsychological development in a community with methylmercury exposure from seafood

“…In addition, the persistence of methylmercury and the continuing maternal exposure through intake of contaminated food make both pre-and postnatal exposures of babies likely in breastfed children. Infants may not have the capacity to eliminate methylmercury because of the lack of demethylating bacteria in the gut (Rowland, 1988;Rowland et al, 1984). The exact timing of this colonization is unknown, and considerable interindividual variation may exist.…”

“…Breastfeeding is known to reduce the risk of a wide range of diseases, including both life-threatening and less serious ailments (Amin-Zaki et al, 1980;Rowland et al, 1984;Saarinen and Kajosaari, 1995;Gartner et al, 1997), and the World Health Organization has therefore extended its recommendation of the length that the infant should be breastfed exclusively from 4 to 6 months or longer (World Health Assembly Resolution 25, 2002). Breastfeeding is also associated with an advantage in subsequent mental development, as indicated by global neurological and cognitive development.…”

In-depth review of atmospheric mercury: sources, transformations, and potential sinks

“…In addition, mercury(II) can be converted to methylmercury by microorganisms in the intestinal tract. 30 The half-life of inorganic mercury compounds in the body is reported to be approximately 40 days. 27 The most common organometallic mercury(II) compound in environmental systems is methylmercury.…”

Human Milk as a Source of Methylmercury Exposure in Infants.

“…According to experimental studies, methylmercury elimination depends on the presence of demethylating bacteria in the gut (10,11). These bacteria tend to become established after weaning and then metabolize methylmercury from the bile into mercuric ions that are eliminated with the feces; unconverted methylmercury is reabsorbed from the gut.…”

“…Without taking into account possible differences in susceptibility to methylmercury exposure, the PTWI would then correspond to a milk Weaning-sampling interval (months) Figure 2. Mercury concentration in hair of 12-month-old infants who had been nursed no more than 5 (10,11). Exactly when such bacteria colonize the gut is unknown, and interindividual variation could be considerable.…”