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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

Author:
Zheng, Xinmei, Zhu, Yuting, Liu, Chunsheng, Liu, Hongling, Giesy, John P., Hecker, Markus, Lam, Michael H. W., Yu, Hongxia
Source:
Environmental Science & Technology 2012 v.46 no.23 pp. 12943-12951
ISSN:
1520-5851
Subject:
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)
Abstract:
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.
Agid:
5344549