title: Actions of oestrogens and antioestrogens on rat mammary gland development: relevance to breast cancer prevention.
abstract: The proliferative actions of a series of antioestrogens on the development of the second thoracic mammary gland of ovariectomized immature Sprague-Dawley rats have been investigated. Evidence is presented that shows trans-tamoxifen, LY 117018 and LY 139481, like oestradiol-17 beta and cis-tamoxifen, promote full mammary gland ductal development and induce a high rate of cell proliferation in the undifferentiated epithelial cells of the terminal end buds, the main growth region for ductal growth. Conversely, ICI 164,384, a new antioestrogen, is without effect on ductal elongation. In vivo exposure of trans-tamoxifen and LY 117018 treated glands in medically castrated animals to the carcinogen DMBA, results in a high rate of mammary tumour development. Indeed, the actions of these so-called antioestrogens are equivalent to those observed in oestradiol-treated rats.
authors.affiliation: Tenovus Institute for Cancer Research, University of Wales College of Medicine, The Heath, Cardiff.
authors.forename: R I
authors.initials: RI
authors.lastname: Nicholson
authors.forename: K E
authors.initials: KE
authors.lastname: Gotting
authors.forename: J
authors.initials: J
authors.lastname: Gee
authors.forename: K J
authors.initials: KJ
authors.lastname: Walker
mesh_terms: D000375:Aging; D000818:Animals; D001943:Breast Neoplasms / Q000517:prevention & control; D002453:Cell Cycle / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000254:growth & development; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
chemical_list: D004965:Estrogen Antagonists; D004958:Estradiol