Hereditary analysis of the strain difference of methylmercury distribution in mice

Hereditary analyses of strain differences in the distribution of methylmercury (MeHg) were carried out with various strains of mice. First, dose-response relationships were examined with 6-week-old male mice of four strains at seven dose levels from 0.25 to 6.0 mg CH3HgCl/kg. Significant strain differences in dose-response were found for both blood and brain. Second, the frequency distribution of blood mercury concentration was examined with two inbred strains, C3H and C57BL, their hybrid (F1), F2 generation, and back-cross mice. The F1 generation showed an intermediate value between their parents, and characteristic hereditary segregations were found in the frequency of blood mercury concentration in F2 and back-cross mice. Third, the relationship between blood mercury concentration and the molecular structure of mouse hemoglobins (Hb) was examined with 14 strains of inbred mice and a single wild mouse strain. Five strains with Hb-beta d and one strain with Hb-beta p showed blood mercury concentrations twice as high as the other Hb-beta strains. Through these experiments, Hb structure, especially the number and position of cysteinyl residue in the molecule, was found to play a primary role in binding with MeHg and in determining blood mercury concentration.