The effects of prolactin, growth hormone and insulin on the total uptake and specific binding of tritiated dihydrotestosterone in the cultured rat ventral prostate were examined. In similar conditions prolactin and insulin act synergistically with testosterone on the macromolecule synthesis of the prostate, but have no effect on the conversion of testosterone to dihydrotestosterone.
The total uptake of tritiated dihydrotestosterone to the tissues was slightly, but not statistically significantly, increased by prolactin, insulin and growth hormone. The majority of the radioactive dihydrotestosterone in the tissue was in free form or very loosely bound. None of these three hormones altered the binding of tritiated dihydrotestosterone to the cytoplasmic receptors.
Non-radioactive dihydrotestosterone, cyproterone and cyproterone acetate in 1000 foid excess strongly decreased the binding of tritiated dihydrotestosterone to the cytoplasmic reseptors and to the nuclei. That part of the binding, which was inhibited by the hormones was considered to represent the specific binding to the receptors. Insulin stimulated both the specific and the unspecific uptake of dihydrotestosterone to the nuclei. Prolactin only stimulated the specific uptake to the nuclei while growth hormone had no effect.
Autoradiography of the nuclear fraction indicated a firm binding of tritiated dihydrotestosterone to the nuclei. The radioactivity of the other contaminating cell components in this fraction appeared to be negligible.