High-affinity binding of estrone, estradiol and estriol in human cervical myometrium and cervical and vaginal epithelium.

The estrogen receptor concentrations in the cervical myometrium and ectocervical and vaginal epithelium were very low soon after the menstrual bleeding. The receptor concentrations were considerably higher in the middle of the proliferative phase and in postmenopausal patients treated with vaginal estrogens. In these two groups the estrogen receptor concentrations were lowest in the vaginal epithelium and highest in the cervical myometrium. In all three tissues studied, estradiol had the highest affinity to the receptor protein, followed by estriol and estrone. The binding was specific for all three estrogens whereas a 1000-fold excess of progesterone, dihydrotestosterone and testosterone was required in order to obtain competition for the estrogen receptor. Sedimentation analysis showed that estriol and estradiol were bound to macromolecules sedimentation analysis showed that estriol and estradiol were bound to macromolecules sedimenting at 9.0 S and 3.5-4.6 S whereas estrone was bound only to the 4.6 S binding protein.