Modulation of tamoxifen-specific binding sites and estrogen receptors by estradiol and progesterone in the neonatal uterus of guinea pig.
Estradiol administration to newborn guinea pigs (30 ng/g body wt) provokes an 84 +/- 10% and 145 +/- 10% (means +/- SE) increase of tamoxifen-specific binding site (site B) in the uterine cytosol and in the 0.6 M KCl nuclear extract, respectively, 48 h after hormone administration. The simultaneous injection of progesterone (15 micrograms/g body wt) with estradiol antagonizes this estrogen-induced increase of site B. Parallel modifications of estrogen receptor are observed following the same estradiol treatment: after translocation to the nuclear fraction, cytoplasmic estrogen receptor is replenished 24 h after hormone administration with a net increase of 60 +/- 10% (mean +/- SE) after 48 h. The increase of estrogen receptor is also antagonized by the simultaneous administration of progesterone. It is concluded that the levels of both tamoxifen-specific binding site and estrogen receptor are modulated by estradiol and progesterone in the neonatal uterus of guinea pig.
D000818:Animals; D000831:Animals, Newborn; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D007700:Kinetics; D011374:Progesterone / Q000494:pharmacology*; D011955:Receptors, Drug; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism*; D013629:Tamoxifen / Q000378:metabolism; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*
D011955:Receptors, Drug; D011960:Receptors, Estrogen; D013629:Tamoxifen; D011374:Progesterone; D004958:Estradiol