John Wiley & Sons, Ltd.

Exposure to a PBDE/OH‐BDE mixture alters juvenile zebrafish (Danio rerio) development

Polybrominated diphenyl ethers (PBDEs) and their metabolites (e.g. hydroxylated BDEs (OH‐BDEs)) are contaminants detected together frequently in human tissues, and are structurally similar to thyroid hormones (TH). THs partially mediate metamorphic transitions between life stages in zebrafish, making this a critical developmental window which may be vulnerable to chemicals disrupting thyroid signaling. In this study, zebrafish were exposed to 6‐OH‐BDE‐47 (30 nM) alone or to a low (30 µg/L) or high dose (600 µg/L) mixture of PentaBDEs, 6‐OH‐BDE‐47 (0.5‐6 µg/L), & 2,4,6 tribromophenol (TBP) (5‐100 µg/L) during juvenile development (9‐23 dpf) and evaluated for developmental endpoints mediated by TH signaling. Fish were sampled at three time points and examined for developmental and skeletal morphology, apical thyroid and skeletal gene markers, and modifications in swimming behavior (as adults). Exposure to the high mixture resulted in > 85% mortality within one week of exposure, despite being below reported acute toxicity thresholds for individual congeners. The low mixture and 6‐OH‐BDE‐47 groups exhibited reductions in body length and delayed maturation, specifically relating to swim bladder, fin, and pigmentation development. Reduced skeletal ossification was also observed in 6‐OH‐BDE‐47 treated fish. Assessment of thyroid and osteochondral gene regulatory networks demonstrated significantly increased expression of genes that regulate skeletal development and THs. Overall, these results indicate that exposures to PBDEs/OH‐BDEs mixtures adversely impact zebrafish maturation during metamorphosis. This article is protected by copyright. All rights reserved

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