title: Progesterone antagonizes the effects of estradiol in the fetal uterus of guinea pig.
abstract: The antagonistic effect of progesterone on estrogen responses in the uterus of the guinea pig fetus has been demonstrated. The administration of 5 mg of progesterone to estradiol-primed pregnant guinea pigs inhibits the increase in uterine wet weight normally occurring between 1 and 2 days after estradiol treatment. Progesterone also decreased the concentration of its own receptor by as much as 51%, 4 days after treatment. Progesterone had no effect on the replenishment of estrogen receptor in the cytosol but it induced a rapid decrease in nuclear receptor since 5 days after estradiol treatment the concentration of nuclear estrogen receptor is 2.0 +/- 0.65 pmol/mg DNA while only 24h after progesterone treatment this value is 0.78 +/- 0.10 pmol/mg DNA which is not significantly different from the untreated control values of 0.68 +/- 0.12 pmol/mg DNA. It is concluded that progesterone can antagonize estrogen action in the fetal uterus.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D005333:Fetus / Q000187:drug effects*; D006168:Guinea Pigs; D009929:Organ Size / Q000187:drug effects; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology*; D011960:Receptors, Estrogen / Q000187:drug effects; D011980:Receptors, Progesterone / Q000187:drug effects; D014599:Uterus / Q000187:drug effects* / Q000378:metabolism
chemical_list: D004965:Estrogen Antagonists; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D011374:Progesterone