Dissociated effects of tamoxifen on growth and on progesterone receptor induction in quail oviduct
1991
Laugier, C. | Fanidi, A. | Dufrene, L. | Fayard, J.M. | Pageaux, J.F.
The estrogen agonist and antagonist activities of tamoxifen on growth and progesterone receptor induction were studied in the immature quail oviduct. Tamoxifen alone, when administered for 3 days at doses ranging from 0.01-10 mg/kg. had no effect on oviducal weight, DNA, and protein content, but significantly increased progesterone receptor concentration. When combined with estradiol benzoate (0.1 mg/kg daily for 3 days), tamoxifen completely inhibited the trophic action of estradiol while it only reduced the progesterone receptor concentration in the oviduct by 50%. This latter effect reflected more a reduction in the progesterone-responsive cell population of the tissue rather than a true estrogen antagonist effect on this specific protein induction. These results and previous data from this laboratory support the conclusions that in this model system: (1) the mechanisms involved in the induction of estrogen-sensitive cell proliferation and progesterone receptor synthesis are independent, and (2) the estrogen-antagonist activity of tamoxifen on cell proliferation is mediated through an estrogen receptor-independent pathway. Thus, the immature quail oviduct model system is particularly relevant to more detailed studies on the molecular modes of action of synthetic antiestrogens.
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