Screening The Developmental Toxicity Of Contaminants Using Xenopus Tropicalis Embryos

The Embryo Teratogenesis Assay is a valid method to detect the developmental toxicity of contaminants. It is a trend to use embryos to take instead of individuals in the test of toxicity and research of toxicology in the future. The Forg Embryo Teratogenesis Assay-Xenopus (FETAX) has been widely used in the developmental toxicity test of contaminants and environmental samples. In this paper, a mode of action-based detection method would be built using Xenopus tropicalis embryos.Firstly, Xenopus tropicalis embryos were exposed to 0.025～0.8 mg·L-1 Cu2+ and 0.05～6 mg·L-1 Cd2+ for 48 hours. Malforamtions were found in multiple organs, including eyes, mouths, guts and tails. The sensitivity of X. tropicalis to the contaminants is similar to that of X. laevis.Secondly, X. tropicalis embryos were exposed to a typical deiodinase inhibitor, iopanoic acid (IOP). The results showed that 0.5～5 mg·L-1 IOP significantly induced hypopigmentation in eyes, abnormal size and even absence of eyes. T3 showed no effect on the development of embryos, but it significantly enhanced IOP-induced teratogenic effects. These results indicated that thyroid hormone signal might be involved in the IOP-induced teratogensis.Thirdly, X. tropicalis embryos were exposed to tetrabromobisphenol-A (TBBPA) for 48 h. The results showed that 0.01～1 mg·L-1 TBBPA induced abnormal eyes, skin hypopigmentation, enlarged proctodaeum, narrow fins and pericardial edemas. Similarily, T3 significantly enhanced TBBPA-induced teratogenic effects.Finally, X. tropicalis embryos were exposed to 2-50μg·L-1 all-tans retinoic acid (RA) for 48h. RA induced abnormal eyes, reduction in brain and bent notchord. These malformatios were greatyl different from those induced by IOP or TBBPA.In brief, new animal model X. tropicalis can take instead of X. laevis in FETAX. Different contaminants indcued different malformations, which provids the clues to reveal the mechanisms of teratogens. Therefore, X. tropicalis embryos can be developed as a mode action-based detection method of devlopmental toxicity if FETAX is further modified.