Alterations in thyroid function in female Sprague-Dawley rats following chronic treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin. 1995

C H Sewall, and N Flagler, and J P Vanden Heuvel, and G C Clark, and A M Tritscher, and R M Maronpot, and G W Lucier
National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.

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.

UI MeSH Term Description Entries
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D011863 Radioimmunoassay Classic quantitative assay for detection of antigen-antibody reactions using a radioactively labeled substance (radioligand) either directly or indirectly to measure the binding of the unlabeled substance to a specific antibody or other receptor system. Non-immunogenic substances (e.g., haptens) can be measured if coupled to larger carrier proteins (e.g., bovine gamma-globulin or human serum albumin) capable of inducing antibody formation. Radioimmunoassays
D003577 Cytochrome P-450 Enzyme System A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism. Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450
D004790 Enzyme Induction An increase in the rate of synthesis of an enzyme due to the presence of an inducer which acts to derepress the gene responsible for enzyme synthesis. Induction, Enzyme
D005260 Female Females
D005786 Gene Expression Regulation Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation. Gene Action Regulation,Regulation of Gene Expression,Expression Regulation, Gene,Regulation, Gene Action,Regulation, Gene Expression
D000072317 Polychlorinated Dibenzodioxins Dibenzodioxin derivatives that contain multiple chloride atoms bound to the benzene ring structures. TCDD,Tetrachlorodibenzodioxin,2,3,7,8-Tetrachlorodibenzo-p-dioxin,Chlorinated Dibenzo-p-dioxins,Dibenzo(b,e)(1,4)dioxin, 2,3,7,8-tetrachloro-,PCDD,Polychlorinated Dibenzo-p-dioxins,Polychlorinated Dibenzodioxin,Polychlorodibenzo-4-dioxin,Polychlorodibenzo-p-dioxin,Tetrachlorodibenzo-p-dioxin,Chlorinated Dibenzo p dioxins,Dibenzo-p-dioxins, Chlorinated,Dibenzo-p-dioxins, Polychlorinated,Dibenzodioxin, Polychlorinated,Dibenzodioxins, Polychlorinated,Polychlorinated Dibenzo p dioxins,Polychlorodibenzo 4 dioxin,Polychlorodibenzo p dioxin,Tetrachlorodibenzo p dioxin
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001483 Base Sequence The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence. DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D012333 RNA, Messenger RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm. Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated

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