Determination of the binding properties of estradiol-17β within the cytoplasmic and nuclear fractions of rat ventral prostate

Abstract

A specific binding protein for estradiol-17β (E217β) has been detected in the cytosol of the ventral prostate of retired breeder CD strain rats. The binding protein was determined to have a sedimentation coefficient of 3.6 S by ultracentrifugation of [3H]-estradiol-17β labeled cytosol on high salt sucrose density gradients. The estrogen binding protein appears to have a greater affinity for diethylstilbestrol and estradiol-17β than for estrone or estriol. Also, the estrogen binding protein appears to be inactivated by sulfhydryl group blocking agents.The uptake of radioactivity by ventral prostate nuclei was investigated following the injection of [3H]-E2-17β in vivo. A radiolabeled protein with a sedimentation coefficient similar to the cytoplasmic estrogen binding protein was detected in the 0.6 M KC1 extract of the purified nuclei. However, in vitro studies with purified ventral prostate nuclei failed to detect a temperature dependent nuclear translocation of cytoplasmic protein-steroid complex. These studies indicate that an estrogen binding protein with some of the properties of a receptor is present in rat ventral prostate. However, the physiological significance of this protein has not been determined.