RAT THYMIC ESTROGEN-RECEPTOR .2. PHYSIOLOGICAL-PROPERTIES

Specific, high affinity estrogen receptor has been shown to be present in the rat thymus. From in vivo and in vitro studies as well as competition assays, the receptor possesses specificity for estradiol and the estrogen-like compound diethylstilbestrol, but not for progesterone, testosterone, triamcinolone or cortisol. By sucrose gradient centrifugation studies the thymic estrogen receptor was shown to have a sedimentation value of 7-8s in low salt buffer. Castration resulted in a decrease in thymic estrogen receptor in terms of pmol/g tissue or fmol/mg soluble protein but no change in terms of pmol/mg DNA. Estradiol injection in vivo resulted in a rapid decrease of measurable cytoplasmic receptor by 2.5 min, which became undetectable by 20 min and returned to control values by 24 h. Autoradiographic studies show that the radioactive label is concentrated in single cells which may be of the reticulo-epithelial variety. © 1979.