Effects of carbon tetrachloride on embryonic development studied in the post-implantation rat embryo culture system and in chick embryos in ovo.

The effects of carbon tetrachloride on embryonic development were investigated in a mammalian and a non-mammalian system. In the former, whole-rat embryos, taken at 9.5 days of gestation, were exposed in vitro to different concentrations of CCl(4) (10, 100, 300, 600 and 1000 mug/ml) in rat serum with or without a rat liver microsomal activating system (S-9 mix). In the latter system, chick embryos in ovo were exposed to different concentrations of CCl(4) vapour (25, 35 and 75 ppm). When studied in the whole-rat embryo culture system without metabolic activation, concentrations of up to 300 mug CCl(4)/ml had no effect on the overall development. Concentrations -600 mug CCl(4)/ml affected the somite number, growth and morphology of the embryos, which can be interpreted as general toxicity. In the presence of S-9 mix, toxicity occurred at concentrations -300 mug/ml. In ovo exposure to CCl(4) showed that 25 ppm caused a decrease in the number of somites. At 35 ppm, CCl(4) induced further toxicity, as indicated by reduced somite number and growth and increased malformation rates. The results indicate that effects on morphogenic events appeared in both systems at concentration levels that also affected the overall development and that, independently of the choice of species or route of administration, CCl(4) has no potential to induce specific malformation patterns. The presence of a metabolic system in the rat embryo cultures approximately doubled the toxicity of CCl(4).