Binding of Cytoplasmic 5α-Dihydrotestosterone-Receptor Complex by Nuclei from the Ventral Prostate, Liver, and Spleen of Rats

Abstract

Cytoplasmic ³H-5α-dihydrotestosterone-receptor complex of the rat ventral prostate was efficiently taken up by nuclei isolated from the liver, the ventral prostate and the spleen. The amount of the complex bound to liver nuclei was approximately 3 times that to prostate nuclei, and a relatively small amount of the complex was taken up by spleen nuclei under the incubation conditions: 0.16nM complex (2.0mg as protein) was used. Binding of the complex to liver nuclei was low-affinity and non-saturable, while in nuclei from the ventral prostate and the spleen, high-affinity and saturable binding was observed. K_d of nuclear binding in the latter two tissues was roughly of the order of 10-70M. Castration caused a reduction in the binding of the complex to prostate nuclei and replacement therapy with testosterone propionate completely blocked the effect of castration on the nuclear binding. The affinity of high-affinity binding was not changed significantly after castration. No significant effects of castration and testosterone treatment were observed in the binding of nuclei from the other two tissues examined.
The physiological significance of the nuclear binding of hormone-receptor complexes in the action of steroid hormones is discussed.