Some properties of androgen-binding activity in rat testis.
High-affinity (Ka approximately equal to 5 X 10(8) M-1 for testosterone) androgen-binding activity in rat testis was shown to have a rapid dissociation rate constant (t1/2 = 3 min, 0 degrees C, 30% glycerol buffer) using dextran-coated charcoal to separate bound from free hormone. Because of this fact, exchange of endogenous and labeled hormone was complete in the assay incubation time (16 h, 0 degrees C) and Scatchard plots of the high-affinity binding data were shown to measure total as contrasted to available sites. The binding was highly specific for androgens. Polyacrylamide gel electrophoresis separated high-affinity androgen-binding protein (Rf 0.54) from albumin (Rf 0.62). Binding site estimates under saturating conditions or by Scatchard analysis of electrophoresis data utilizing [3H]dihydrotestosterone agreed reasonably well with estimates made by the charcoal technique using [3H]testosterone.
D000818:Animals; D001665:Binding Sites; D013196:Dihydrotestosterone / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004822:Epididymis / Q000378:metabolism; D007016:Hypophysectomy; D007700:Kinetics; D008297:Male; D010902:Pituitary Gland / Q000502:physiology; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
D011506:Proteins; D011956:Receptors, Cell Surface; D013196:Dihydrotestosterone; D013739:Testosterone