2 ESTROGEN RECEPTORS IN REPRODUCTIVE TISSUE

In both chick oviduct and in the human uterus two distinct high affinity low capacity estrogen binding proteins have been demonstrated in the cytoplasm. These components are specific for estrogens and have equilibrium dissociation constants (KD) of 10-10 and 10-9 M as determined by Scatchard analyses. Two binding components of similar affinities can also be detected in nuclei isolated from oviducts and uteri which had been exposed to estrogen. Since reproductive tissue from such widely divergent species contains two highly specific high affinity estrogen binding proteins it would appear that the presence of two putative estrogen receptors is a general phenomenon and therefore warrants careful consideration when one attempts to explain the molecular mechanism of steroid hormone action. © 1979.