Failure of zinc acetate to reduce ethylenethiourea-induced fetal anomalies in rats

Abstract

Ethylenebisdithiocarbamate of manganese (maneb) and zinc (zineb) and their degradation and metabolic product, ethylenethiourea (ETU), have produced similar teratogenic anomalies in rats. The mode of teratogenicity of maneb, deduced from the protective effects of zinc acetate following their simultaneous administration, has been attributed to its ability to chelate zinc. Whether ETU has a similar mode of action was investigated. Mated females from five control groups were fed a standard diet for the entire period of pregnancy. Dams in five other groups were fed the standard diet to which 0.0444% zinc (as zinc acetate) was added during the period from the 11th to the 14th day of pregnancy. On the 13th day of pregnancy, control dams and those given supplemental zinc were not treated, treated with distilled water, or with 80, 120, or 160 mg/kg ETU sc. A necropsy was performed on some dams 3 hr postinjection and concentrations of zinc were measured in the conceptus and maternal serum. The remaining dams were sacrificed and a necropsy performed on the 22nd day of gestation and their fetuses were examined for external, visceral, or skeletal anomalies. Zinc acetate was ineffective in reducing ETU-induced malformations, and concentrations of zinc in the conceptus and maternal serum were not affected by feeding zinc acetate or injecting ETU.