Effects of methylmercuric chloride administered to pregnant rats during the preimplantation period.

Female rats were treated on Day 1, 2, 3, 4, or 5 of pregnancy with 5 mg/kg methylmercuric chloride ip. Some dams were killed on Day 5 of gestation in order to evaluate toxic effects on the early embryos or blastocysts. The remaining rats were sacrificed at the end of pregnancy to verify any embryofetotoxic and teratogenic effects. Unlike what has been found by other authors with in vitro experiments, no clear toxic effects in the blastocyst on Day 5 of pregnancy were evident. A slight embryofetotoxic effect was found when the females were killed at the end of pregnancy.