Young intact and adult gonadectomized C3H male and female mice were utilized as bioassay models to detect endocrine disruption chemicals. Animals treated with oestradiol (E) or progesterone (Prog) or E plus Prog were used to assess steroid hormone agonist and antagonist activities of 4-OH-tamoxifen (TAM), diethylstilbestrol (DES) and genistein (GEN) by bioassay. The stimulation or inhibition of mammary growth by TAM depended on sex, the state of animal (intact or gonadectomized), hormonal treatment (Prog, E, E plus Prog) and dose of TAM. TAM stimulated mammary growth in untreated ovariectomized (OV-X) females and in Prog-treated intact males and OV-X females. In intact males, mammary growth was increased by TAM at dose 0.1-1 microg day(-1) and decreased at dose 10 microg day(-1). Mammary growth was inhibited by TAM in Prog-treated intact females and in E or E plus Prog-treated intact and gonadectomized males and females. Uterine weights were increased by TAM in both untreated and treated (E, Prog, E plus Prog) intact and OV-X females; however, seminal vesicle weights were decreased by TAM in both untreated and treated (E, Prog, E plus Prog) intact males. DES alone affected mammary growth (an inverted-U-shaped dose-response curve) both in male and female mice. DES increased uterine weights; however, seminal vesicle weights were decreased. GEN increased mammary and uterine growth in OV-X females, GEN plus Prog stimulated mammary growth in intact males. The results obtained in these studies show clearly that only a bioassay consisting of several endpoints reflective to the mechanism of oestrogen and anti-oestrogen action has the ability to evaluate activities of a molecule.

This study tested and compared the anti-proliferative and proliferative activities of two anti-oestrogens and three anti-progestins on four separate mouse model systems: young intact and adult ovariectomized (OV-X) females, and young intact and adult castrated males. Pure steroidal anti-oestrogen ICI 182,780 (ICI) decreased mammary and uterine growth stimulated by endogenous hormones in young intact females and by exogenous hormones [progesterone (Prog), 17beta-oestradiol (E) or E plus Prog] in both young intact and adult ovariectomized (OV-X) females. Non-steroidal anti-oestrogen EM-800 (EM), on the other hand, had no effect on mammary and uterine growth stimulated by endogenous hormones in young intact females and in adult OV-X females. Uterine growth was even stimulated by EM alone, and a combination of EM plus Prog not only stimulated uterine growth but also mammary growth (an oestrogenic agonistic activity). However, EM showed anti-oestrogenic activities in both mammary and uterine tissues in females treated with E or E plus Prog. In males, ICI and EM decreased mammary growth stimulated by exogenous hormones (E or E plus Prog) in both young intact and adult castrated animals. In young intact, but not in adult castrated males, ICI increased seminal vesicle growth affected by both endogenous and exogenous (Prog, E or E plus Prog) hormones. EM, on the other hand, decreased seminal vesicle weights in E or E plus Prog and increased its weights in Prog-treated young intact males. Thus, under certain conditions EM possess mixed agonist and antagonist activity in the mammary gland, uterus and seminal vesicles. Norethindrone acetate (NA)-stimulated mammary growth was decreased by anti-progestins onapristone (ON), RU 46556 (RU), and RU 38486 (MI) by 34-59% in females and by 35-93% in males. Uterine weights of NA-treated females were decreased by ON and RU by 29-55% but not by MI. In NA-treated young intact males, seminal vesicle weights were stimulated by RU (by 63%) and not affected by ON and MI. In NA-treated adult castrated males, seminal vesicle weights were decreased by ON, increased by RU and not affected by MI. The results obtained in these and our earlier studies show clearly that mouse four-model systems could serve as in vivo tool for the detection of steroid hormone agonist and antagonist activities of natural and man-made chemicals.

Previously it has been shown that measuring of the percent area of mammary fat pad occupied by mammary epithelial structures is a suitable parameter for bioassay estrogenicity and for the assessment of mixture effects of estrogenic agonists and antagonists. The purpose of the present study was to investigate how estradiol (E), progesterone (Prog) and E plus Prog dose dependently affect the number of terminal end buds (TEBs) and the number of ductal branchings in young intact (18-dayold) and adult gonadectomized male and female (OV-X, ovariectomized between 21-24 days of age; OV-X) C3H mice and assess if the number of the TEBs and ductal branchings are suitable supplemental parameters for estrogenicity bioassay. The results demonstrate that in animals treated with E or E valerate (EV) a classic biphasic dose-response curve was obtained. The lower doses of E or EV (0.001-0.1 µg.d -1 ) increased both the number of TEBs (mainly large buds) and ductal branchings, whereas the higher doses (1 and 10 µg.d -1 ) were inhibitory. In young intact females doseresponse studies with Prog alone revealed that the number of TEBs and the degree of ductal banchings progressively increased from the dose of 125 µg.d -1 and reached a higher level than that achieved in animals treated with E alone. However, in adult OV-X females Prog increased number of small TEBs from dose 250 µg.d -1 but the increase in ductal branching was not significant. Both parameters were lower than those achieved in animals treated with E alone. Prog alone at high (1000 µg.d -1 ) dose only slightly increased number of TEBs in young intact males but had no effect on number of both TEBs in castrated males and on the number of ductal branchings in both young intact and adult castrated males. In young intact females treated with different doses (0.001 -10 µg.d -1 ) E plus Prog (500 µg.d -1 ), the number of TEBs and the number of ductal branchings was not significantly different from that in animals treated with Prog alone. However, in OV-X females E plus Prog increased the number of both TEBs and ductal branchings when compared with OV-X females treated with Prog alone. In males E also synergized the effect of Prog in stimulation of both the number of TEBs and the number of ductal branchings. High dose (10 µg.d -1 ) of E in combination with Prog decreased number of both TEBs and ductal branchings in males and OV-X females.Mice, mammary epithelium growth, estradiol, progesterone

The changes in mammary, uterine and seminal vesicle growth were intended to identify the in vivo activity of estrogen antagonists. Using the combinations of hormone agonist and antagonist, we tested and compared four model systems, the young intact and adult gonadectomized male and female mice. Steroidal antiestrogen ICI 182 780 (ICI) always behaved as an antiestrogen: ICI alone or in combination with estradiol (E) or progesterone (Prog) decreased mammary and uterine growth in prepubertal and adult ovariectomized (OV-X) females and decreased mammary growth in prepubertal adult castrated males treated with E. In prepubertal males ICI alone or in combination with Prog or E also increased seminal vesicle weights. Nonsteroidal antiestrogen EM-800 (EM) alone, on the other hand, had no effect on mammary and uterine growth in prepubertal females, and in adult OV-X females uterine growth was even stimulated by EM alone, and a combination of EM plus Prog stimulated not only uterine growth but also mammary growth ( the estrogenic effects). EM synergized with E in decreasing seminal vesicle weights in E treated prepubertal males. However, EM decreased E stimulated mammary growth in prepubertal and adult gonadectomized females and males and E stimulated uterine growth in prepubertal and adult OV-X females. EM increased Prog stimulated seminal vesicle weights in prepubertal males (the antiestrogenic effects). Antiestrogen, growth, mammary gland, uterus, seminal vesicles, miceEstrogens and progesterone regulate the development and maintenance of the female reproductive system. Despite the classical contention that estrogen is the female hormone, compelling evidence indicates a pivotal role of estrogen in the regulation of development and function of several systems in the male (Tena-Sempere et al. 2000). In the male, the physiological role of estrogens involves multiple actions, from masculinization of brain areas related to reproductive function and sexual behavior to regulation of testicular development and function, as well as direct effects on bone and the cardiovascular system Sharpe 1998).Many of the biological effect of estrogens are mediated by their binding to nuclear receptors. Nuclear hormone receptors represent an evolutionary conserved class of transcription factors being present from flies to mammals (Beato et al. 1995). Upon binding the estrogenic compound, the transcriptionally inactive estrogen receptor (ER) undergoes conformational (activating ) changes that facilitate the interaction of receptor with specific palindromic DNA sequences (estrogen response elements) within the regulatory regions of target genes as liganded receptor dimers. However, all estrogenic compounds do not produce the same conformation of receptors, and the ability of ligand-bound receptors to regulate target gene transcription is determined by the cell-and tissue-specific expression of both different coactivator and corepressor proteins that impact the ER signalling pathway (Paige et al. 1999). Adding to this complexity there are two E...

Köhlerová E., J. Kotanová, J. ·karda: Biological Responses of Antiprogestins in Mammary Gland, Uterus and Seminal Vesicles of Prepubertal Intact and Adult Gonadectomized Mice. Acta Vet. Brno 2006, 75: 319-328.The present study tested and compared the antiproliferative and proliferative activities of three antiprogestins on four separate mouse model systems: prepubertal intact and adult ovariectomized (OVX) females, prepubertal intact and adult castrated males. In prepubertal intact males and females and adult castrated males, norethindrone acetate (NA; a synthetic steroid exhibiting progestational and estrogenic activities)-stimulated mammary growth was decreased by antiprogestins: more by RU 46556 (RU) than RU 38486 (MI) and onapristone (ON) . In adult OVX females the inhibitory effect of RU and MI was lower than that of ON. Uterine weights were not significantly decreased by MI, were significantly decreased by RU at a lower daily dose (50 µg) but not affected by a high (500 µg) dose. Seminal vesicle weights were increased by RU but not affected by MI in both NA-treated prepubertal and adult castrated males. In adult castrated but not in prepubertal males ON decreased seminal vesicle weights. In 17β-estradiol (E) plus progesterone (Prog)-treated animals of all four model systems, RU (100 µg/d) acted additively with a submaximal daily dose (10 µg) of antiestrogen ICI 182, 780 (ICI) to produce a lower mammary gland growth rate than ICI alone. In uterus, however, no significant effect of a combination of ICI plus RU was noted when compared with ICI alone. In general, our assay could serve as an in vivo tool for the detection of steroid hormone agonist and antagonist activities of newly synthesized analogs of steroid hormones, and natural and man-made chemicals and extracts of environmental samples.