title: Progesterone "receptor" in rat ovary.
abstract: A soluble thermolabile protein with many characteristics of a progesterone receptor has been identified in ovaries of estrogen-stimulated, hypophysectomized, immature female rats. A potent synthetic progestin R5020 (17,21-dimethyl-19-nor-pregna-4, 9-diene-3, 20-dione) and a progestin-receptor complex stabilizer (glycerol) were employed. After the incubation of [3H]R5020 with ovarian cytosol, fractionation of a Sephadex G-200 column revealed a peak of radioactivity which eluted with the void volume. This peak, which represented saturable binding, disappeared after heating (37 C for 20 min) and trypsinization. In the absence of glycerol, binding decreased by 84%. Scatchard analysis of the binding curve showed the R5020 binding to be of moderately high affinity (Kd  4 nM), with 232 fmol binding sites/mg cytosol protein. Binding site number rose linearly with increasing cytosol protein concentration. The relative abilities of various steroids to inhibit [3H]R5020 Binding were: R5020 greater than progesterone greater than estradiol greater than testosterone greater than cortisol greater than diethylstilbestrol. [3H]R5020 was not metabolized and did not bind specifically to serum. In summary, we have identified a protein with characteristics of a progesterone receptor in the cytoplasmic fraction of ovarian tissue.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D003600:Cytosol / Q000378:metabolism; D004054:Diethylstilbestrol / Q000494:pharmacology; D005260:Female; D007016:Hypophysectomy; D007700:Kinetics; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D011397:Promegestone / Q000378:metabolism; D051381:Rats; D011980:Receptors, Progesterone / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011980:Receptors, Progesterone; D004054:Diethylstilbestrol; D011397:Promegestone