中文摘要：

本文旨在探讨低剂量PCBs和PBDEs单一暴露和复合暴露的甲状腺干扰作用.非洲爪蟾46期蝌蚪单独或共暴露于100 ng·L^-1 Aroclor 1254和BDE-209至62期.暴露结束后检测变态时间、甲状腺组织学结构、甲状腺相关基因表达水平等指标.结果发现,Aroclor 1254和BDE-209单独暴露使蝌蚪变态发育呈现一定的延迟趋势,而复合暴露却显著抑制蝌蚪变态发育;所有的暴露处理均导致蝌蚪甲状腺组织代偿性改变,表现为胶质面积减少,甲状腺滤泡上皮细胞高度显著增加;Aroclor 1254单独暴露显著抑制甲状腺激素受体（TRA）、Ⅱ和Ⅲ型脱碘酶（DI-2,DI-3）的表达,BDE-209单独暴露仅抑制DI-2的表达,但BDE-209协同促进Aroclor1254对肝脏内TRA表达的抑制作用.综上,低剂量Aroclor 1254和BDE-209单独暴露和复合暴露对非洲爪蟾变态发育具有一定的甲状腺抑制作用,复合暴露的抑制作用明显高于单一暴露的作用.鉴于甲状腺系统在脊椎动物生长发育过程中的重要作用,低剂量PCBs和PBDEs复合暴露的甲状腺干扰效应应该受到格外关注.

英文摘要：

This study aimed to investigate potential thyroid-disrupting effects of single and combined exposure to polychlorinated biphenyl（ PCBs） and polybrominated diphenyl ethers（ PBDEs） at low concentrations. Xenopus laevis tadpoles were exposed to Aroclor 1254（ 100 ng·L^-1） and/or BDE-209（ 100 ng·L^-1） from stage 46 to 62. At the end of exposure,metamorphosis time,histological structure of the thyroid glands,and expression levels of thyroid-related genes were examined. The results were as follow： a metamorphosis delay trend was found among the tadpoles in the single exposure groups,while the tadpoles following co-exposure exhibited a significant metamorphosis delay. All treatments caused compensatory histological changes in the thyroid glands,including decreased colloid area and increased height of follicular epithelial cells. Aroclor 1254 exposure significantly inhibited the expression levels of thyroid hormone receptor betaA（ TRA）,type Ⅱdeiodinase（ DI-2） and type Ⅲ deiodinase（ DI-3）. BDE-209 exposure only inhibited the DI-2expression level. However,BDE-209 synergistically improved Aroclor 1254-induced suppressive effect on the TRA mRNA expression level in liver. Taken together,single or combined exposure to Aroclor 1254 and BDE-209 at low concentrations had suppressive effects on the thyroid system during X. laevis metamorphosis. Co-exposure exhibited more obvious suppressive effects compared with single exposure. Given the crucial role of the thyroid system in the growth and development ofvertebrates,the thyroid-disrupting effects of co-exposure to PCBs and PBDEs at low concentrations should receive great attention.