Methyl Mercuric Chloride Toxicokinetics in Mice. II: Sexual Differences in Whole‐Body Retention and Deposition in Blood, Hair, Skin, Muscles and Fat

This article reports the time course for deposition of methyl mercury administered as a single oral dose in whole body, total carcass, liver, kidneys, brain, blood, fat, muscle, bone, skin and hair of male and female Bom:NMRI mice. The whole‐body elimination initially approximated first order kinetics with half‐times around 7 days and 12 days for males and females respectively, although a decreased elimination rate was observed during the last 10 days. The elimination of mercury from carcass was slower than the elimination from the whole‐body, causing an increasing relative carcass deposition with time in both male and female mice and explaining the observed deviation from first order elimination kinetics. Thus, first order kinetics is observed only during 2‐3 weeks after dosage. Throughout the experimental period, male mice had significantly lower levels of mercury in both blood, brain and muscles than had female mice, whereas renal deposition of mercury in male mice was significantly higher than in female mice. At day 30 the females had about twice as much mercury in liver, brain and hair (median values) as had male mice. Despite the fact that comparable whole‐body retention and carcass deposition were observed in male and female mice, the blood concentrations in male mice was only about half that in female mice. Furthermore, half‐times for mercury in blood did not differ much between male and female mice and were close to whole‐body half‐time in male mice, although the absolute amounts of mercury in both blood and whole‐body at day 20 were significantly different. The large sexual differences in mercury levels in tissues compared with the more limited differences in half‐times and the fact that several organs have different mercury levels already at day 3 after dosage, although the whole‐body levels are more or less equal, indicate extensive differences in the methyl mercury toxicokinetics between male and female Bom:NMRI mice.