title: Further characterization of the androgen receptor in rat testis.
abstract: Immature rat testes contain a specific binding protein for testosterone (T) and 5alpha-dihyrotestosterone (DHT) with physico-chemical properties similar to the cytoplasmic androgen receptors in the epididymis and ventral prostate but different from the testicular androgen-binding protein (ABP). Like the androgen receptors in the prostate and epididymis, it has a sedimentation coefficient of about 7 S at low ionic strength, is eluted in or close to the void volume on Sephadex G-200 gel filtration (Stokes radius greater than 80 A), has an isoelectric point of about 5.6-6.0 (mean) 5.8 and a relative mobility (Rf) of 0.4 in 3.25% acrylamide gels. Following the injection of 3H-labeled testosterone, T and DHT are bound selectively by the receptor. Relatively more [3H]T than [3H]DHT is present in bound and free fractions as well as in total testicular 105,000 g supernatant. Similar results are obtained from testicular incubations with equimolar amounts of [3H]T and [3H]DHT at 0 degrees C in vitro. Saturation of receptor sites is achieved by incubation of testis supernatants with increasing amounts of [3H]T at 0 degrees C. The number of available binding sites following post-hypophysectomy regression is estimated to be about 9 fmoles/mg protein, and the apparent equilibrium constant of dissociation is 7 X 10(-10) M. The temperature stability and sulfhydryl dependence of the testicular androgen receptor are similar to androgen receptors in other organs. Binding is destroyed by heating the supernatants at 50 degrees C for 30 min and by exposure to p-chloromercuriphenylsulfonate (1 mM) at 0 degrees C for 60 min. Furthermore, like other androgen receptors, the half-time of dissociation of testicular androgen-receptor complexes at 0 degrees C is extremely slow (t1/2 greater than 35 h). Separation of seminiferous tubules from interstitial tissue showed that a major portion of these receptors were localized within the seminiferous tubules.
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001798:Blood Proteins / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D013196:Dihydrotestosterone / Q000378:metabolism*; D007016:Hypophysectomy; D007700:Kinetics; D008297:Male; D009994:Osmolar Concentration; D011485:Protein Binding; D011506:Proteins / Q000302:isolation & purification; D051381:Rats; D011956:Receptors, Cell Surface; D012671:Seminiferous Tubules / Q000378:metabolism; D013696:Temperature; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
chemical_list: D001798:Blood Proteins; D011506:Proteins; D011956:Receptors, Cell Surface; D013196:Dihydrotestosterone; D013739:Testosterone