Extrathyroidal Effects of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin on Thyroid Hormone Turnover in Male Sprague-Dawley Rats

A. G. Schuur
1997 Endocrinology  
Treatment of rats with different polyhalogenated aromatic hydrocarbons strongly decreases plasma T 4 , with little or no decrease in plasma T 3 . The extrathyroidal effects of 2,3,7,8-tetrachlorodibenzop-dioxin (TCDD) on thyroid hormone turnover were studied by ip administration of a single dose of 10 g TCDD/kg BW or vehicle (corn oil) to euthyroid (Eu) rats, thyroidectomized (Tx) rats, and Tx rats infused with 1 g T 4 (TxϩT 4 ) or 0.4 g T 3 (TxϩT 3 )/100 g BW⅐day by osmotic minipumps. Tx rats
more » ... minipumps. Tx rats showed decreased plasma T 4 and T 3 and increased plasma TSH levels, decreased hepatic type I deiodinase (D1) and malic enzyme activities, and increased brain type II deiodinase (D2) activities. All parameters were largely restored to Eu levels in TxϩT 4 rats and, except for plasma T 4 and brain D2 activity, in TxϩT 3 rats, validating the thyroid hormone-replaced Tx rats as models to study the peripheral effects of TCDD. Three days after
doi:10.1210/en.138.9.3727 pmid:9275058 fatcat:li7kg6rj7bekxjsfzgefxhxfu4