[Studies on estradiol occupied and unoccupied receptors in human endometrial cytosol and nucleus: steroid receptors throughout the menstrual cycle and in cases of oral contraceptives administration (author's transl)].

Occupied and unoccupied estradiol (E3) receptors were investigated by exchange assay in cytosol and nuclear extract of human endometrium. Cytosol E2 and progesterone (P) unoccupied receptors and nuclear occupied E2 receptor were measured throughout the menstrual cycle and in the tissues from patients administered oral contraceptives. Sedimentation profiles of these receptors were also studied; and following results were obtained: 1) No occupied E2 receptor was observed in cytosol and almost all of those were of unoccupied type. In nuclear extract, only 0-25% of receptor was of unoccupied type and the other receptor was of occupied type. 2) Highest binding activities of cytosol E2 and P receptors were found in late proliferative phase. Maximum binding sites (Bm) were 630 and 380 f mol/mg protein and dissociation constant (Kd) was 8.9 +/- 0.7 and 4.7 +/- 0.4 x 10(-10) M, respectively. In nuclear extract, binding peaks were observed in late proliferative and late secretory phase. Bm was 1.5 f mole/microgram DNA and Kd was 12.7 +/- 1.0 x 10(-10) M.