title: Effects of neonatally-administered 17beta-estradiol on induction of mammary carcinomas by 7, 12-dimethylbenz[a]anthracene in female rats.
abstract: Various doses of 17beta-estradiol (E2) were administered subcutaneously to inbred female Sprague-Dawley (SD) rats once at birth. At 50 days after birth, rats in all the groups were given 10 mg of 7, 12-dimethylbenz[a]anthracene (DMBA). In the 1000 microg group, the incidence and number of mammary carcinomas were markedly low, while in the 10 microg group, a large number of mammary carcinomas was noted. Corpora lutea were observed in all rats in the control, 0.1, 1, 10 and 100 microg groups at 50 days old; however, no corpora lutea were observed in any rat in the 1000 mg group at age 50 days and at sacrifice. Observation of the whole-mount specimens showed a low number of terminal end buds (TEBs) in the 1000 microg group and a high number in the 10 microg group. It is suggested that neonatal administration of E2 affects the gonadotropin-secreting system, resulting in a decrease of progesterone, which is thought to influence the progression of mammary carcinomas induced by DMBA. Moreover, neonatal administration of E2 directly affects the mammary glands, and it is suggested that E2 may promote differentiation of TEBs resulting in inhibitory effects on the initiation of mammary carcinomas.
authors.affiliation: The Department of Tumor Pathology, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan. funato-mamoru@snbl.co.jp
authors.forename: Mamoru
authors.initials: M
authors.lastname: Funato
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kawaguchi
authors.forename: Takao
authors.initials: T
authors.lastname: Hori
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yoshikawa
authors.forename: Kentaro
authors.initials: K
authors.lastname: Gejima
authors.forename: Hideo
authors.initials: H
authors.lastname: Kawashima
authors.forename: Syuhei
authors.initials: S
authors.lastname: Taguchi
authors.forename: Kenjirou
authors.initials: K
authors.lastname: Ninomiya
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Umekita
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Nagata
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yoshida
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000818:Animals; D000831:Animals, Newborn; D002273:Carcinogens / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000473:pathology*; D051381:Rats
chemical_list: D002273:Carcinogens; D004958:Estradiol; D015127:9,10-Dimethyl-1,2-benzanthracene