Teratogenicity of cadmium chloride in the South African frog, Xenopus laevis

The teratogenicity of cadmium chloride was tested by the FETAX (Frog Embryo Teratogenesis Assay: Xenopus) procedure. In five assays, groups of Xenopus embryos were grown in media containing concentrations of 0.75-56 mumol/l; controls were incubated in medium without cadmium chloride. Exposures began 5 h post-fertilization and ended 101 h post-fertilization. In control groups, > 95% of embryos survived at 101 h and the incidence of malformations was < 7%. In Cd(2+)-exposed groups, concentration-dependent mortality and numerous malformations were observed, including gut malrotation, ocular anomalies, bent notochord, misshapen fin, facial dysplasia, cardiac deformities and dermal blisters. Other abnormalities included stunted growth and hypopigmentation. The minimum concentration of cadmium chloride that inhibited growth was 18 mumol/l. The median embryolethal concentration (LC50) was 32 (SE +/- 4) mumol/l; the median teratogenic concentration (EC50) was 3.7 (SE +/- 1) mumol/l; the teratogenic index (TI = LC50/EC50) was 8.6. This study demonstrates that cadmium chloride is teratogenic for Xenopus laevis and provides a standardized experimental model for studying the molecular mechanisms of cadmium teratogenesis.