title: Exposure to2,2',4,4'-tetrabromodiphenyl ether (BDE-47) alters thyroid hormone levels and thyroid hormone-regulated gene transcription in manila clam Ruditapes philippinarum.
abstract: Polybrominated diphenyl ethers (PBDEs) have the potential to disturb the thyroid endocrine system in vertebrates, but little is known about the disruptive effects of PBDEs on marine bivalves. In this study, we first examined the effects of BDE-47 exposure on growth of juvenile manila clams Ruditapes philippinarum. The result showed that 1.0 and 10 μg L(-1) BDE-47 had adverse effects on 14-d shell-length growth of juvenile clams. Then, one-year-old adult clams were exposed to 0, 0.1 and 1 μg L(-1) BDE-47 for 15 d. BDE-47 (1 μg L(-1)) exposure caused significant decreases of total T4 (thyroxine) by 40% and T3 (3,5,3'-triiodothyronine) by 75% concentrations in haemolymph of the clams. Transcription of genes involved in thyroid hormone synthesis and metabolism were also studied by quantitative RT-PCR. Gene expression levels of sodium iodide symporter (rp-NIS), iodothyronine deiodinase (rp-Deio) and thyroid peroxidase (rp-TPO) were increased in a dose-dependent manner at day 5 and day 10, while monocarboxylate transporter 8 (rp-Mct8) was downregulated at day 5, day 10 and day 15. The effect and preliminary mechanism observed in the present study were consistent with the results from previous studies on rodent and fish, implying that exposure to BDE-47 may pose threat to thyroid hormone homeostasis in bivalves through thyroid synthesis and metabolism pathways. This study may provide a first step towards understanding of the thyroid function disruptive effects of PBDEs on marine bivalves and the underlying mechanism across taxonomic groups and phyla.
authors.affiliation: The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Song
authors.affiliation: The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, PR China. Electronic address: jmiao@ouc.edu.cn.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Miao
authors.affiliation: The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, PR China.
authors.forename: Luqing
authors.initials: L
authors.lastname: Pan
authors.affiliation: The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D055768:Halogenated Diphenyl Ethers / Q000633:toxicity*; D007453:Iodide Peroxidase / Q000235:genetics; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D055768:Halogenated Diphenyl Ethers; D014874:Water Pollutants, Chemical; D014284:Triiodothyronine; C511295:2,2',4,4'-tetrabromodiphenyl ether; D007453:Iodide Peroxidase; D013974:Thyroxine
keywords: BDE-47; Gene expression; Growth; Ruditapes philippinarum; Thyroid hormone