title: [Androgen binding components in the human placenta].
abstract: In the present study, characterization of the androgen binding components in human term placenta was undertaken. Scatchard analysis revealed the presence of high affinity binding components with dissociation constants (Kd) of 1.5 X 10(-10)M and 3.7 X 10(-9)M for dihydrotestosterone (DHT) in hormone-striped placental cytosol. Isoelectric focusing (IEF) after equilibration with 20 nM 3H-DHT indicated three binding activities with elution pH (Pe) of 4.6, 5.3 and 6.0. The placental cytosol was then fractionated into Concanavalin-A Sepharose (Con-A). The Con-A unbound fraction contained two heat labile binding populations for DHT with Kd's of 1.9 +/- 0.4 X 10(-10)M and 5.9 +/- 1.2 X 10(-9)M (mean +/- SE: n = 6), and two peaks on IEF with 20nM 3H-DHT with Pe's of 4.6 and 6.0. When IEF was performed with 2 nM 3H-DHT, only one peak was observed with a Pe of 6.0. The Con-A bound fraction contained a heat stable, single binding population for DHT with a Kd of 2.2 +/- 0.2 X 10(-10)M and a Pe of 5.0. It appears that the binding population is testosterone-estradiol binding globulin (TeBG). In competitive binding studies, androstenedione, dehydroepiandrosterone and dehydroepiandrosterone-sulfate had much higher affinities for Con-A unbound fraction than Con-A bound fraction. Therefore, it appears that there are at least two androgen binding components in human term placental cytosol, demonstrable after removal of TeBG contamination, that can be shown to have different affinities for DHT and, probably, separate Pe's.
mesh_terms: D000727:Androgen-Binding Protein / Q000032:analysis*; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000032:analysis*; D003208:Concanavalin A; D003600:Cytosol / Q000032:analysis; D013196:Dihydrotestosterone / Q000378:metabolism; D005260:Female; D006801:Humans; D007525:Isoelectric Focusing; D010920:Placenta / Q000032:analysis* / Q000378:metabolism; D011247:Pregnancy; D011944:Receptors, Androgen / Q000032:analysis; D012738:Sex Hormone-Binding Globulin / Q000032:analysis*
chemical_list: D000727:Androgen-Binding Protein; D002352:Carrier Proteins; D011944:Receptors, Androgen; D012738:Sex Hormone-Binding Globulin; D013196:Dihydrotestosterone; D003208:Concanavalin A