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LACK OF ALTERATIONS IN THYROID HORMONES FOLLOWING A SINGLE POSTNATAL EXPOSURE TO POLYBROMIANTED DIPHENYL ETHER 47.
Citation:
GEE, J. R., J. M. HEDGE, P. PHILLIPS, K. MCDANIEL, AND V. C. MOSER. LACK OF ALTERATIONS IN THYROID HORMONES FOLLOWING A SINGLE POSTNATAL EXPOSURE TO POLYBROMIANTED DIPHENYL ETHER 47. Presented at Society of Toxicology, Charlotte, NC, March 25 - 29, 2007.
Description:
Polybrominated diphenyl ethers (PBDEs) are commonly used as commercial flame retardants in a variety of products including plastics and textiles. There has been a rapid accumulation of these chemicals in the environment and high levels of PBDEs have been found in the adipose tissue, blood, and breast milk of humans. This is especially true for the congener, 2,2',4,4'-tetrabromodiphenyl ether (BDE 47), which has shown an accelerated accumulation in humans in recent years. Concern over BDE 47 exposure has also stemmed from the similarity of its molecular structure with that of polychlorinated biphenyls (PCBs) which are known to disrupt thyroid hormone homeostasis. Furthermore, there are reports of thyroid alterations following perinatal exposure to PBDE mixtures. Disruption of thyroid hormone levels has been shown to be important in development of the brain due to its role in neurite outgrowth, synapse formation, and neuronal guidance. Thus disruptions in thyroid hormone levels may underlie certain behavior deficits observed in animals following PBDE exposure, such as reduced habituation and learning and memory abnormalities. The aim of this study was to determine whether a single exposure to BDE 47 in C57BL/6 mice would alter thyroid hormone levels during a phase of rapid brain development. Male mice were dosed with either 0 (corn oil vehicle), 1, 10, or 30 mg/kg on postnatal day 10, and sacrificed for collection of serum at 1, 5, or 10 days after the dose (n=5-6 litters/dose/time point). Body weight gain was not altered. Total thyroxine (T4) and triiodothyronine (T3) were measured by RIA. No effects of BDE 47 were observed on the T4 levels at any age examined; T3 assays on remaining sera (n=2-5/dose/time point) also showed no changes. This indicates that alterations in thyroid hormone levels may not contribute to the purported behavior abnormalities seen in mice following acute neonatal exposure to BDE 47. This is an abstract of a proposed presentation and does not reflect US EPA policy.