Testicular Estradiol Receptors in the Rat

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Abstract
Investigations concerning a biochemical explanation for the mechanism of action of steroids have revealed the presence of specific receptors for steroids in target tissues. Specific steroid, binding receptors in testicular tissue have only recently been studied, although in 1969 Stumpf (1) presented autoradiographic evidence for a nuclear localization of radioactivity in interstitial cells of the immature rat testis after administration of radioactive oestradiol. In the course of a study on steroid receptors in the testis we observed specific binding of oestradiol by the cytoplasm of the rat testis tissue (2, 3). It appeared of interest to investigate if the binding for this steroid fulfills the criteria for a true steroid receptor, i. e. high affinity binding of steroid, saturability, steroid specificity and tissue specificity. Data will be given on the specific localization of this receptor in interstitial tissue obtained after wet dissection of mature rat testis and on the characterics of oestradiol binding by the cytoplasmic macromolecule. In addition, it will be reported that after in vivo or in vitro administration of oestradiol, this steroid can be bound by nuclear fractions isolated from rat testis interstitial cells (4). The distribution of high affinity oestradiol binding components in the different tissues of the male rat was also studied. The highest amount of specific oestradiol binding macromolecules per cell were found in testis interstitial cells and in the pituitary, smaller amounts were present in epididymis, prostate, adrenal and liver. Finally, results will be presented on agar gel electrophoresis of the oestradiol receptor, a specific androgen receptor and androgen binding protein from rat testis.