Thyroid And Reproductive Endocrine Disruption By Decabromodiphenyl Ether (BDE-209) And Cadmium (Cd) In Xenopus Laevis

PBDE (Polybrominated diphenyl ethers, PBDEs), one of brominated flame retardants, were widely used in a variety of industries. Nowadays, PBDEs have become a major persistent organic pollutant. Cadmium (Cd) contamination, like other heavy metal pollution, possesses the characteristics of abundance in resources, long retention time, cumulation, transfer and enrichment along the food chain, detection and restoration difficulty if the environment has been contaminated, etc. In animal experiments, PBDEs and Cd have been proven to cause developmental neurotoxicity, thyroid and reproductive endocrine disruption.In this thesis, first of all, the recent research progress in toxicology study on PBDEs and Cd is introduced and several problems in this research field are summarized. The advantages of Xenopus lavies in toxicology study are discussed, and introduced the application of X. laevis in embryo toxicity, thyroid disruption and reproductive endocrine disruption.Considering limited toxicity data on BDE-209 and Cd, which has been widely existed, the effects of thyroid and reproductive endocrine disruption of single and combined exposure to BDE-209 (100 ng/L) and Cd (1μg/L) at environmentally relevant doses in X. laevis were studied.The final conclusions of the research are the following:(1) The short-term exposure to BDE -209 at environmental related doses did not affect the growth process of Xenopus laevis and also did not affect the development induced by triiodothyronine (T3);(2) The long-term exposure to BDE -209 and/or Cd at environmental related doses had thyroid disrupting effects on X. laevis;(3) The long-term exposure to BDE -209 and/or Cd at environmental related doses did not significantly effect the development of ovaries. However, Cd single exposure and combined exposure cause certain damage on the testes of X. laevis.In summary, BDE-209 and Cd at environmentally relevant doses had thyroid and reproductive endocrine disruption on X. laevis. The toxical effects and mechanisms of PBDEs and heavy metal interaction remain to be furthered investigated.