John Wiley & Sons, Ltd.

Relationships between polybrominated diphenyl ethers, transcription and activity of type 1 deiodinase in a gull highly exposed to flame retardants

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Deca‐brominated diphenyl ether (deca‐BDE) mixture, composed mainly of BDE‐209, is subject to usage restrictions in North America and Europe, although global action on its continued use has yet to be undertaken. Relatively large concentrations of PBDEs, especially BDE‐209 and its higher‐brominated degradation products, have been reported in tissues of ring‐billed gulls (Larus delawarensis) breeding near the densely‐populated city of Montreal (QC, Canada). There is limited knowledge of BDE‐209 biotransformation and toxicokinetics in birds. Deiodinases, a class of enzymes catalyzing thyroid hormone conversion, have been suggested to be involved in BDE‐209 debromination in birds. The objective of this study was to investigate the relationships between PBDE concentrations and type 1 deiodinase (D1) transcription and in vitro activity (microsomes) in liver of Montreal‐breeding ring‐billed gulls. Ring‐billed gulls exhibiting highest D1 activity in liver microsomes accumulated the greatest liver concentrations of hepta‐ and octa‐BDEs. Activity of D1 was inversely related to concentration ratios of BDE‐209 to octa‐ and ∑hepta‐BDE. An even stronger inverse relation was found between D1 activity and BDE‐209 to ∑nona + octa + hepta‐BDE concentration ratios. The mRNA levels of D1 in liver of gulls were inversely associated with liver concentrations of ∑octa‐BDE. The present findings suggest that D1 is potentially involved in BDE‐209 biotransformation and accumulation of higher‐brominated PBDEs in liver of ring‐billed gulls. This article is protected by copyright. All rights reserved

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