Methylmercury toxicity: in vivo evaluation of teratogenesis and cytogenetic changes

Mercury is a major environmental pollutant and a proven teratogen in both animals and man. Different dose levels of methylmercuric chloride (30, 25, 15 and 5 mg/kg of body weight) were administered to pregnant ICR strain mice on day 9 of pregnancy. On gestational day 18 the animals were laparotomized. A significant increase in fetal toxicity was observed at all dose levels, except following treatment with 5 mg/kg. A marked reduction in the mean weight of fetuses from treated animals (5 mg/kg) was observed compared to the controls. Higher levels of mercury were found in maternal blood and in fetal tissues of treated animals compared to the corresponding controls. Chromosome stickiness and clumping were observed in all tissues examined (e.g., bone marrow, spleen, lung, liver) from the fetuses of treated animals. The frequency of SCEs'/cell in bone marrow cells was similar to that of controls. The results demonstrate that methylmercuric chloride, the most toxic of mercuric compounds, causes chromosome stickiness and clumping leading to reduced mitotic divisions.