title: 2,3,7,8-tetrachlorodibenzo-p-dioxin potentially attenuates the gene expression of pituitary gonadotropin β-subunits in a fetal age-specific fashion: a comparative study using cultured pituitaries.
abstract: Our previous studies have demonstrated that maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes a reduction in gonadotropin biosynthesis in the fetal pituitary, resulting in the attenuated expression of steroidogenic proteins in the fetal gonads and the impairment of sexual behaviors in adulthood. However, the mechanism of the attenuation remains unknown. To address this issue, we investigated whether TCDD affects the pituitary production of gonadotropins, using cultured pituitary. In the absence of gonadotropin-releasing hormone (GnRH), a regulator of gonadotropin biosynthesis, TCDD did not affect the expression of gonadotropin mRNAs both in fetal and postnatal pituitaries. On the other hand, in the presence of GnRH, TCDD interfered with the synthesis of gonadotropin β-subunit mRNAs only in the fetal pituitary. A protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate) and a PKA activator (8-bromoadenosine-3' 5'-cyclic monophosphate) induced the expression of gonadotropin mRNAs in the fetal pituitary. Among the subunits, only the induction of β-subunit was reduced by TCDD treatment. These results suggest that TCDD reduces gonadotropin biosynthesis via damage to GnRH-stimulated PKC and PKA signaling in a β-subunit- and fetal age-specific manner.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Takeda
authors.forename: Midori
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Masaru
authors.initials: M
authors.lastname: Himeno
authors.forename: Shinji
authors.initials: S
authors.lastname: Takechi
authors.forename: Tadatoshi
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Takumi
authors.initials: T
authors.lastname: Ishida
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ishii
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Yamada
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D005333:Fetus / Q000166:cytology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D005865:Gestational Age; D006065:Gonadotropins, Pituitary / Q000235:genetics* / Q000378:metabolism; D008297:Male; D009924:Organ Culture Techniques; D010902:Pituitary Gland / Q000187:drug effects* / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D004785:Environmental Pollutants; D006065:Gonadotropins, Pituitary; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D015124:8-Bromo Cyclic Adenosine Monophosphate; D013755:Tetradecanoylphorbol Acetate