Cytosol and nuclear estrogen receptor in the genital tract of the rhesus monkey

Estrogen receptor levels of cytosol and nuclei were measured in the cervix, vagina, myometrium, and endometrium of the rhesus monkey after the following experimental treatments: (1) castration; (2) castration with estradiol treatment; and (3) castration with estradiol plus progesterone treatment. Plasma hormone levels similar to those of normal menstrual cycles were achieved by implantation of silastic capsules containing estradiol or progesterone. The K D , 4 × 10 −9 M, for the cytosol receptor was similar in all tissues. Competition studies showed cytosol receptor affinities to be E 2 > e 1 > E 3 > DES. Cytosol receptor levels in estrogenized animals were lowered by progesterone treatment. Progesterone treatment did not alter the levels of nuclear receptor indicating that the lower levels of cytosol receptor obtained with progesterone were not due to nuclear translocation of cytosol receptor. Estrogen treatment changed the sedimentation coefficient of the endomentrial and myometrial cytosol receptor from 4 s to 8 s when compared with the castrate. This alteration in sedimentation coefficient was blocked by progesterone treatment. Changes in sedimentation coefficient were not observed in the cervix or vagina. Nuclear receptor in estrogen and estrogen plus progesterone treated animals sedimented as a 5 s protein. The data suggest that both qualitative and quantitative changes in the estradiol cytosol receptor of the genital tract are induced by progesterone and that these alterations may be related to the hormone interactions in target organs.