Nuclear binding sites in the liver for dexamethasone and in the ventral prostate for R1881

Nuclear binding sites which exhibit affinity similar to previously reported "Type II" sites (Clark et al., 1978) for estradiol in rat uterus were found in the liver and ventral prostate of rats and showed a binding specificity for glucocorticoid and androgen, respectively. However, both binding sites were qualitatively different from those of the rat uterus; a reducing agent, dithiothreitol, did not block the binding of steroids in the liver and ventral prostate. Extraction of the bound ligands discriminated the binding of the liver from that of the ventral prostate, Triton X-100 solubilized a majority of the bound Dex in liver nuclei, while the effect of KCl treatment was more remarkable on the bound R1881 in nuclei of the ventral prostate. Castration caused a drastic decrease in the binding of ventral prostate, only trace binding was observed at 48 h after hormone deprivation and replacement therapy restored the binding rapidly, at 3 h after testosterone injection almost 70% of the binding was detected. Although adrenalectomy did not result in a profound change in the binding sites of liver, the injection of Dex increased the number of binding sites significantly. The physiological significance of these binding sites is not clear at the present time.