EMBRYOCIDAL AND TERATOGENIC EFFECTS OF METHYLMERCURY IN MICE

Effects of methylmercury hydroxide (MeHgOH) [environmental toxicant] were determined in 3 strains of mice, C57BL/6J, CD and 129/SvSl. In single dose experiments, a dose of 0, 2, 4, 8 or 12 mg/kg of MeHgOH was administered by various routes to all 3 strains of pregnant mice on day 10 of gestation. For multiple dose experiments, a daily dose of 0, 2, 4, 6, 8 or 10 mg/kg was injected s.c. to 129/SvSl mice from days 7-12 of gestation. The fetotoxic effects were examined on day 18 of gestation. Embryocidal and teratogenic effects were noted in all 3 strains of mice. Cleft palate was the most frequently observed teratogenic malformation. Other malformations, such as anophthalmia, micrognathia, exencephaly, missing limbs and facial deformity, were seen infrequently. Multiple dose administration of MeHg to pregnant dams caused a higher incidence of teratogenesis with a lower incidence of maternal toxicity in comparison to single dose administration. All 3 species of mice investigated were susceptible to the teratogenic effects of MeHg.