title: Low level exposure to the flame retardant BDE-209 reduces thyroid hormone levels and disrupts thyroid signaling in fathead minnows.
abstract: Polybrominated diphenyl ether (PBDE) flame retardants have been shown to disrupt thyroid hormone regulation, neurodevelopment, and reproduction in some animals. However, effects of the most heavily used PBDE, decabromodiphenyl ether (BDE-209), on thyroid functioning remain unclear. This study examined low-dose effects of BDE-209 on thyroid hormone levels and signaling in fathead minnows. Adult males received dietary exposures of BDE-209 at a low dose (∼3 ng/g bw-day) and high dose (∼300 ng/g bw-day) for 28 days followed by a 14-day depuration to evaluate recovery. Compared to controls, fish exposed to the low dose for 28 days experienced a 53% and 46% decline in circulating total thyroxine (TT4) and 3,5,3'-triiodothyronine (TT3), respectively, while TT4 and TT3 deficits at the high dose were 59% and 62%. Brain deiodinase activity (T4-ORD) was reduced by ∼65% at both doses. BDE-209 elevated the relative mRNA expression of genes encoding deiodinases, nuclear thyroid receptors, and membrane transporters in the brain and liver in patterns that varied with time and dose, likely in compensation to hypothyroidism. Declines in the gonadal-somatic index (GSI) and increased mortality were also measured. Effects at the low dose were consistent with the high dose, suggesting nonlinear relationships between BDE-209 exposures and thyroid dysfunction.
authors.affiliation: Nicholas School of the Environment, Duke University , Durham, North Carolina, United States.
authors.forename: Pamela D
authors.initials: PD
authors.lastname: Noyes
authors.forename: Sean C
authors.initials: SC
authors.lastname: Lema
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Macaulay
authors.forename: Nora K
authors.initials: NK
authors.lastname: Douglas
authors.forename: Heather M
authors.initials: HM
authors.lastname: Stapleton
mesh_terms: D000818:Animals; D001823:Body Composition / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D003530:Cyprinidae / Q000235:genetics / Q000502:physiology*; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D029941:Fish Proteins / Q000378:metabolism*; D005411:Flame Retardants / Q000378:metabolism / Q000633:toxicity*; D008401:Gas Chromatography-Mass Spectrometry; D005786:Gene Expression Regulation; D055768:Halogenated Diphenyl Ethers / Q000378:metabolism / Q000633:toxicity*; D007453:Iodide Peroxidase / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011897:Random Allocation; D011988:Receptors, Thyroid Hormone / Q000378:metabolism; D012098:Reproduction / Q000187:drug effects; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000187:drug effects; D013963:Thyroid Hormones / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
chemical_list: D018076:DNA, Complementary; D029941:Fish Proteins; D005411:Flame Retardants; D055768:Halogenated Diphenyl Ethers; D008565:Membrane Proteins; D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D013963:Thyroid Hormones; D014874:Water Pollutants, Chemical; D007453:Iodide Peroxidase; C010902:decabromobiphenyl ether
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