title: Characterization of unoccupied (R) and occupied (RA) androgen binding components of the hyperplastic human prostate.
abstract: Saturation protocols were developed for measurement of unoccupied (R) and steroid-occupied (RA) androgen binding components of human hyperplastic prostate. The concentration of unoccupied cytoplasmic binding sites (2 hr incubation at 2 degrees C) for the synthetic androgen R1881 (17beta-hydroxy-17alpha-methyl-estra-4,9,11-trien-3-one) and the synthetic progestin R5020 (17alpha,21-dimethyl-19-norpregna-4,9-diene-3,20-dione) respectively was 10.7 +/- 1.4 and 14.3 +/- 3.2 fmoles per mg cytosol protein and the apparent steroid affinity respectively was 9.6 +/- 0.8 and 1.6 +/- 0.4 x 10(8) M-1. Steroid specificity of the unoccupied cytoplasmic R1881 and R5020 binding sites was similar. When R1881 and R5020 were employed as probes of total, R plus RA, cytoplasmic binding components (20-24 hr incubation at 15 degrees C) saturable binding of R5020 was not detectable. Total cytoplasmic R1881 binding site concentration and apparent affinity for R1881 were 51.7 +/- 3.3 fmoles per mg cytosol protein and 2.7 +/- 0.6 x 10(7) M-1. R5020 was a poor inhibitor of R1881 binding to total cytoplasmic R1881 binding components.
mesh_terms: D001665:Binding Sites; D006801:Humans; D007700:Kinetics; D008297:Male; D011467:Prostate / Q000378:metabolism*; D011470:Prostatic Hyperplasia / Q000378:metabolism*; D011485:Protein Binding; D011944:Receptors, Androgen / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D011944:Receptors, Androgen; D011987:Receptors, Steroid