Estrogen Receptors in Stromal and Epithelial Fractions of the Ventral Prostate of Rats

The cytosol from rat ventral prostates contains two estrogen-binding components that can be separated in a glycerol gradient: a high-affinity (KD = 4.2 X 10(-10) M), low-capacity (110 fmole/mg DNA) species that runs in the 8S region of the gradient, and a lower-affinity (KD = 2.4 X 10(-9) M), higher-capacity (410 fmole/mg DNA) 4S protein. Separation of prostate tissue into stromal- and epithelial-enriched fractions was associated with the disappearance of the latter component. When compared per milligram DNA stromal- and epithelial-enriched fractions contained similar amounts of the high-affinity 8S-binding protein. In vivo estrogen treatment caused a time-related disappearance of the protein from the intact cytosol presumably as a result of translocation. No major differences in the degree of binding to the high-affinity component were observed in rats of different ages. Estrogens seem to exert direct effects on both stromal and epithelial tissues of the prostate.