Teratogenic effects of methylmercury in the cat: Note on the use of this species as a model for teratogenicity studies

Pregnancy was induced in cats by coordinating gonadotropin‐induced behavioral estrus and ovulation with natural matings. Reproductive indices were comparable with those already known for pregnancies in normally cycling estrous cats. Cats were orally administered 0, 0.03, 0.83, 0.25, or 0.75 mg/kg Hg (as CH 3 HgCl) from day 10–58 of induced pregnancy and at near term fetuses were delivered by Cesarean section. 0.75 mg/kg caused vomiting, ataxia, and death within 32 days of commencement of treatment. At 0.25 mg/kg there was an increased incidence of abortion and fetal anomalies; in surviving fetuses a reduced neuronal population in the external granular layer of the cerebellum was noticed. Minimal or no embryopathic effects were noted at lower doses. Mercury concentrations were determined and were in the following decreasing order: fetal blood > maternal blood > fetal brain. The blood and the brain of the test dams had similar concentrations. The literature on congenital anomalies in cats is briefly reviewed.