Estradiol Receptor in Rat Testis

Abstract

An estradiol-binding component, sedimenting in the 9.9 ± 0.02 S (SE, n = 28) region by sucrose density gradient centrifugation, was detected in testicular cytosol from 28-day-old rats labeled in vitro with 17β-estradiol-3H. The dissociation constant and the number of binding sites of the component were 4.3 × 10−10M and 1.5 × 10−14moles/mg cytosol protein, respectively. The binding component seemed to be estrogen-specific and a parallel relationship was found between estrogenicity of competing compounds and their binding to the component. Clomiphene citrate decreased the 8H-estradiol binding. Enzyme experiments suggested a protein nature of the component. RNase lowered the 3Hestradiol binding by ca. 40%. No decreased binding activity of the component was observed after storage at —80 C for at least 11 days, in contrast to gradual inactivation at —10 C. From these results, the cytosol from 28-day-old rat testis is concluded to contain an estradiol receptor protein. (Endocrinology94: 902, 1974)