Testicular estradiol receptors in the rat.

Specific high affinity saturable binding proteins for oestradiol-17beta have been demonstrated in the cytoplasm of liver, adrenal, pituitary, prostate, epididymis and testis interstitial tissue of the rat. Specific testicular oestradiol receptors were present in cytoplasmic and nuclear fractions of interstitial tissue, but not in seminiferous tubules of rat testis. After in vivo or in vitro administration of estradiol the steroid was bound by the nuclear fraction of interstitial tissue only in the presence of the cytoplasmic receptor. Using agar gel electrophoresis the cytoplasmic oestradiol receptor from rat testis could be separated from the testicular androgen binding protein (ABP) and from a specific androgen receptor.