Alterations in Thyroid Function in Female Sprague-Dawley Rats Following Chronic Treatment with 2,3,7,8-Tetrachlorodibenzo- p-dioxin

2,3,7,8-Tetrachlorodibenzo- p-dioxin (TCDD) is a multisite carcinogen. Although the hepatocarcinogenic actions of TCDD have received the most attention, it has been demonstrated in several rodent carcinogenicity bioassays that TCDD causes a dose-related increase in thyroid follicular cell adenomas a...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:Toxicology and applied pharmacology 1995-06, Vol.132 (2), p.237-244
Hauptverfasser: Sewall, C.H., Flagler, N., Vandenheuvel, J.P., Clark, G.C., Tritscher, A.M., Maronpot, R.M., Lucier, G.W.
Format: Artikel
Sprache:eng
Schlagworte:
Online-Zugang:Volltext
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:2,3,7,8-Tetrachlorodibenzo- p-dioxin (TCDD) is a multisite carcinogen. Although the hepatocarcinogenic actions of TCDD have received the most attention, it has been demonstrated in several rodent carcinogenicity bioassays that TCDD causes a dose-related increase in thyroid follicular cell adenomas and carcinomas. The purpose of the present experiment was to investigate the dose-response relationship for thyroid function alterations in female Sprague-Dawley rats following chronic treatment with TCDD. TCDD was administered via oral gavage biweekly for 30 weeks at average daily equivalent doses of 0.1-125 ng/kg/day, thereby more than encompassing the dose range historically used in previous TCDD rodent bioassays. The endpoints examined include serum levels of thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH). In addition, the induction of the dioxin-responsive genes UDP-glucuronosyltransferase-1 (UGT1) and cytochrome P450 1A1 (CYP1A1) in liver were measured using reverse-transcriptase-polymerase chain reaction (RT-PCR). In agreement with previous hypotheses, TCDD appears to alter thyroid function via a secondary mechanism, namely increased excretion of T4-glucuronide resulting from TCDD induction of UGT1. The observed follicular cell hyperplasia and hypertrophy are consistent with the observed elevated TSH levels and may represent the early stages in the progression of thyroid carcinogenesis. Therefore, TCDD induces alterations in thyroid hormone function, probably as a result of chronic perturbations of liver-pituitary-thyroid axis.
ISSN:0041-008X
1096-0333
DOI:10.1006/taap.1995.1104