Differences in the fate of methylmercury between mice with and without hair

We investigated time-dependent changes in the fate of methylmercury (MeHg) in both sexes of hairy and hairless mice during 6 days after its single administration to clarify whether the presence of hair could affect tissue distribution and excretion of MeHg. Despite the excretion of mercury (Hg) into hair of hairy mice, Hg concentrations in several but not all tissues were higher in hairy than in hairless mice, especially in the brain, liver, kidney and testes in males and in the brain, liver and blood in females. The cumulative amounts of Hg excreted in feces in males and in both urine and feces in females were lower in hairy than in hairless mice, whereas there was no significant difference in the urinary level in males. However, significant differences in the tissue Hg levels were observed earlier than those in the excretory Hg levels. Accordingly, the higher Hg levels in various tissues of hairy mice as compared to those in hairless mice would not have resulted from the lower Hg excretion levels. These results suggest that the presence or absence of hair markedly affects the fate of MeHg, but the differences in its fate between hairy and hairless mice would not be directly due to the fact that hair provides an excretion route.