title: 2,3,7,8-Tetrachlorodibenzo-p-dioxin increases steady-state estrogen receptor-beta mRNA levels after CYP1A1 and CYP1B1 induction in rat granulosa cells in vitro.
abstract: Previous in-vitro investigations of rat granulosa cells (GC) have shown that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) inhibits estrogen secretion and FSH-induced aromatase activity. Although TCDD exerted no effect on basal aromatase enzyme activity, TCDD did reduce steady-state aromatase mRNA levels in GC using competitive RT-PCR. TCDD is hypothesized to induce these changes through aromatic hydrocarbon receptor(AHR)-mediated gene transcription and the modulation of the estrogen receptor (ER)-signaling pathway. In this study we show that rat GC express mRNA for AHR and the AHR nuclear translocator (ARNT) as well as biomarkers of TCDD action, CYP1A1 and CYP1B1 mRNA. Basal CYP1A1 and ER-alpha mRNAs were present only in trace amounts. By relative RT-PCR analysis we showed that CYP1A1 and CYP1B1 mRNA were induced significantly by TCDD at 6 h and that induction of CYP1A1 was maintained throughout the experiment. Using competitive RT-PCR, we observed no significant change in the mRNA levels of ARNT between control and TCDD-treated GC. Both AHR and ER-beta mRNA levels increased significantly at 48 h with TCDD compared with controls. Since ER-beta mRNA was not increased significantly until 48 h in culture, we suggest that in rat GC, the observed ER-beta mRNA increase by TCDD might be a result of CYP1A1/CYP1B1 catalyzed estrogen metabolism and aromatase mRNA inhibition via AHR.
authors.affiliation: Department of Biological Sciences, 308 Lapham Hall, University of Wisconsin-Milwaukee, 3209 North Maryland Avenue, Milwaukee, WI 53211, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Dasmahapatra
authors.forename: B A
authors.initials: BA
authors.lastname: Wimpee
authors.forename: A L
authors.initials: AL
authors.lastname: Trewin
authors.forename: R J
authors.initials: RJ
authors.lastname: Hutz
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D018929:Cell Culture Techniques; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D047629:Estrogen Receptor beta; D004967:Estrogens / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000187:drug effects / Q000235:genetics*
chemical_list: D047629:Estrogen Receptor beta; D004967:Estrogens; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585499:Cyp1b1 protein, rat; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1