Direct evidence on incorporation of the receptor into the nuclei of rat ventral prostate in the form of the complex with dihydrotestosterone.

Cytosol 9S receptor was prepared from the supernatant fluid at 105,000 X g of rat prostate homogenates by a Sephadex G-100 gel chromatography, and was labeled with 131I. The 131I-labeled 9S receptor retained the activity of forming a complex with 3H-dihydrotestosterone, similarly to the intact cytosol receptor, when examined by a sucrose density gradient centrifugation. When the 131I-labeled cytosol 9S receptor was incubated with isolated prostatic nuclei in the presence of 3H-dihydrotestosterone, it was found that the 131I-labeled receptor was directly incorporated into the nuclei in a form of the complex bound to 3H-dihydrotestosterone. 131I-Labeled receptor-3H-dihydrotestosterone complex which was incorporated into the nuclei was extracted with 0.5 M KCl solution, and the nuclear complex sedimented with a velocity of 5S. The incorporation of 131I-labeled receptor-3H-dihydrotestosterone complex into the nuclei increased along with the raised temperature of incubation, whereas association of the complex with the chromatin reached maximum at 35 degrees C and then decreased gradually beyond this temperature. In the time course study, either the incorporation of the complex into the nuclei or the association with the chromatin reached the maximal levels within 10 min and leveled off up to 60 min. On the other hand, 131I-labeled serum protein was far less efficiently incorporated into the nuclei than the radioiodinated 9S receptor, and association of the serum protein with the chromatin was limited to a very little extent. The 131I-labeled 9S receptor-dihydrotestosterone complex associated with the chromatin was found to be preferably distributed into the non-histone protein as well as the DNA itself of the chromatin. The radioactivity lost by dehistonization of the chromatin was almost negligible. Furthermore, the cytosol 9S receptor fraction bound to 3H-dihydrotestosterone was purified about 100 fold by the two consecutive column chromatographies. The partially purified receptor fraction which was labeled with radioiodine incorporated mostly into non-histone protein and DNA fractions.