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Licensed Unlicensed Requires Authentication Published by De Gruyter June 1, 2005

The Effects of Endocrine-Disrupting Chemicals on Thyroid Hormone Binding to Xenopus laevis Transthyretin and Thyroid Hormone Receptor

  • Kiyoshi Yamauchi , Ryoji Eguchi , Naoyuki Shimada and Akinori Ishihara


We investigated the effects of medical, industrial and agricultural chemicals on 3,3′,5-L-[125I]triiodothyronine ([125I]T3) binding to purified recombinant Xenopus laevis (X. laevis) transthyretin (xTTR), a plasma thyroid hormone-binding protein, and to the ligand-binding domain of thyroid hormone receptor-β (xTR LBD). xTTR derived from X. laevis serum had about 80 times higher affinity for T3 than for L-thyroxine. The xTTR's relative affinities for diethylstilbestrol, pentachlorophenol and ioxynil were 10−1- to 10−2-fold less than that for T3. However, all chemicals investigated had either a weak or no influence on [125I]T3 binding to xTR LBD. The concentration of diethylstilbestrol, the most potent chemical, required for 50% inhibition of [125I]T3 binding to xTR LBD was 104 times greater than that of unlabeled T3. These results indicate the existence of several chemicals that interact with xTTR but not with xTR LBD.

Published Online: 2005-06-01
Published in Print: 2002-12-10

Copyright © 2002 by Walter de Gruyter GmbH & Co. KG

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