Ethylenethiourea: Teratogenicity study in rats and rabbits

Ethylenethiourea (ETU) was administered orally in single daily doses of 0, 5, 10, 20, 40, or 80 mg/kg to nulliparous rats and rabbits. In rats treatment was made from 21–42 days before conception to pregnancy day 15, and on days 6–15 or 7–20 of pregnancy, and in rabbits on days 7–20 of pregnancy. ETU induced meningoencephalocele, meningorrhagia, meningorrhea, hydrocephalus, obliterated neural canal, abnormal pelvic limb posture with equinovarus, and short or kinky tail after 10 mg/kg or more in all rat experiments. Fetal survival was not affected at any dose, whereas fetal growth was retarded at 40 and 80 mg/kg. The incidence of most of the deformities was dose dependent. Results from the rabbit study suggested an increased incidence of resorption sites and decreased brain weight in the group given 80 mg/kg, but no malformations were seen.