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Accumulation and Biotransformation of BDE-47 by Zebrafish Larvae and Teratogenicity and Expression of Genes along the Hypothalamus–Pituitary–Thyroid Axis

Zheng, Xinmei, Zhu, Yuting, Liu, Chunsheng, Liu, Hongling, Giesy, John P., Hecker, Markus, Lam, Michael H. W., Yu, Hongxia
Environmental Science & Technology 2012 v.46 no.23 pp. 12943-12951
Danio rerio, adverse effects, biotransformation, flame retardants, gene expression, genes, iodides, larvae, messenger RNA, prealbumin, sodium, symporters, teratogenicity, thyroglobulin, thyroid hormone receptors, thyroid hormones, thyrotropin receptors, thyrotropin-releasing hormone, toxic substances, transcription (genetics)
Accumulation and effects of BDE-47 and two analogues, 6-OH-BDE-47 and 6-MeO-BDE-47, on ontogeny and profiles of transcription of genes along the hypothalamus–pituitary–thyroid (HPT) axis of zebrafish (Danio rerio) embryos exposed from 4 h post fertilization (hpf) to 120 hpf were investigated. The 96 h-LC₅₀ of the most toxic compound, based on teratogenicity, was 330 μg of 6-OH-BDE-47/L. 6-OH-BDE-47 significantly down-regulated expression of mRNA of thyroid stimulating hormone receptor (TSHR), thyroid hormone receptors (TRs, including TRα and TRβ), sodium/iodide symporter (NIS), and transthyretin (TTR) while up-regulating expression of thyroglobulin (TG) and thyrotropin-releasing hormone (TRH). Spontaneous movement was affected by 1 mg of 6-OH-BDE-47/L or 5 mg of 6-MeO-BDE-47/L. BDE-47 did not alter activity of larvae at any concentration tested. 6-MeO-BDE-47 significantly up-regulated expression of mRNA of TRH, TRα, TRβ and NIS. Both 6-OH-BDE-47 and 6-MeO-BDE-47 affected the thyroid hormone pathway. BDE-47 and 6-MeO-BDE-47 were accumulated more than 6-OH-BDE-47. 6-MeO-BDE-47 was transformed into 6-OH-BDE-47, but BDE-47 was not transformed into it. In summary, the synthetic brominated flame retardant, BDE-47, did not elicit the adverse effects caused by the other two analogues and appeared to have less toxicological relevance than the two natural product analogues 6-OH- and 6-MeO-BDE-47.