Balch Gordon C, Vélez-Espino Luis A, Sweet Colleen, Alaee Mehran, Metcalfe Chris D
Environmental and Resource Studies Program, Trent University, 1600 West Bank Drive, Peterborough, Ont., Canada.
Chemosphere. 2006 Jun;64(2):328-38. doi: 10.1016/j.chemosphere.2005.12.019. Epub 2006 Feb 7.
Tadpoles of the African clawed frog, Xenopus laevis were exposed, beginning at stage 50, to a commercial pentabromodiphenyl ether mixture (DE-71) through the diet. Subsequent experiments were conducted using a single intraperitoneal injection at stage 58 with limited quantities of two purified brominated diphenyl ether (BDE) congeners, BDE47 and BDE99 and DE-71 to determine the relative potency of these BDE congeners within the commercial mixture. Significant inhibition of tail resorption, delayed metamorphosis and impacts on skin pigmentation were observed in Xenopus exposed to DE-71 in the diet at nominal doses of 1000 and 5000 microgg(-1) of food. The estimated time required for 50% of the tadpoles to complete metamorphosis was significantly lengthened in Xenopus exposed to a dietary concentration of 1 microg DE-71 per gram of food. Analysis of PBDEs (sum of 32 congeners) in Xenopus from the treatment with 5000 microgg(-1) of DE-71 indicated that the frogs accumulated an average of 1030 microgg(-1) (wet weight) of PBDEs. In the intraperitoneal injection trials, similar inhibitory responses were observed in Xenopus injected with DE-71 at a nominal dose of 60 microg per tadpole, or injected with BDE47 at a nominal dose of 100 microg per tadpole. No responses were observed in Xenopus injected with BDE99 at doses up to 100 microg per tadpole. Complete inhibition of metamorphosis was observed only in the highest DE-71 dietary treatment. The results of this study are consistent with a mechanism of action of PBDEs involving competitive inhibition of binding of thyroid hormones to transporter proteins, although the mechanism cannot be definitively determined from this study. The observed effects may have occurred through other mechanisms, including sublethal toxicity. The doses used in this study are greater than the levels of PBDEs to which anurans are exposed in the environment, so further studies are required to determine whether exposure to PBDEs at environmentally relevant concentrations can affect frog metamorphosis.
从第50阶段开始，将非洲爪蟾（非洲爪蟾）的蝌蚪通过饮食暴露于一种商用五溴二苯醚混合物（DE - 71）中。随后在第58阶段进行了后续实验，通过向蝌蚪单次腹腔注射有限量的两种纯化的溴化二苯醚（BDE）同系物BDE47和BDE99以及DE - 71，来确定这些BDE同系物在商用混合物中的相对效力。在以每克食物1000和5000微克（-1）的标称剂量通过饮食暴露于DE - 71的非洲爪蟾中，观察到了尾部吸收的显著抑制、变态延迟以及对皮肤色素沉着的影响。在暴露于每克食物1微克DE - 71饮食浓度的非洲爪蟾中，估计50%的蝌蚪完成变态所需的时间显著延长。对用5000微克（-1）DE - 71处理的非洲爪蟾中多溴二苯醚（32种同系物的总和）的分析表明，青蛙平均积累了1030微克（-1）（湿重）的多溴二苯醚。在腹腔注射试验中，在以每只蝌蚪60微克的标称剂量注射DE - 71或以每只蝌蚪100微克的标称剂量注射BDE47的非洲爪蟾中观察到了类似的抑制反应。在以每只蝌蚪高达100微克的剂量注射BDE99的非洲爪蟾中未观察到反应。仅在最高的DE - 71饮食处理中观察到了变态的完全抑制。本研究的结果与多溴二苯醚的作用机制一致，即涉及甲状腺激素与转运蛋白结合的竞争性抑制，尽管从本研究中不能明确确定该机制。观察到的影响可能通过其他机制发生，包括亚致死毒性。本研究中使用的剂量高于环境中无尾两栖动物所接触的多溴二苯醚水平，因此需要进一步研究以确定在环境相关浓度下接触多溴二苯醚是否会影响青蛙变态。
