Effects of oestriol: preliminary results on receptor kinetics in target tissues of postmenopausal women.

This in vivo investigation was done to study the effects of intravaginal oestriol (E3) administration on endometrial, myometrial and vaginal tissue of normal postmenopausal women. All women received intravaginal E3- suppositoria (containing 0.5 mg E3) once a day for 3 weeks prior to hysterectomy. The medication was continued until the day of operation. At the time of operation both uterine and vaginal tissue was obtained. The receptor content in the cytosol was measured by a multiple point-dextran -coated-charcoal assay using [3H]E2 and [3H]ORG-2058 as ligands. The receptor content in the nucleus was measured by incubating purified whole nuclei in 10 nM [3H]E2 for 18 h at 0 degrees C. We have shown that under these conditions there is a total exchange of all occupied receptors. Preliminary data on 4 patients are available. Vaginal cytology clearly showed an increase of the maturation value. Oestrogen receptor concentrations in the cytosol of all three tissues studied were lower than those obtained in untreated women, suggesting nuclear transformation of the receptor as a consequence of treatment. The nuclear E2 receptor levels cannot be compared with normal women yet. Progesterone receptors in endometrial and myometrial cytosol seemed to be higher than those in untreated women, indicating effects of the treatment. In the human, vaginal progesterone receptor cannot be used as a marker for oestrogenic stimulation because only exceptionally could their presence be detected in either treated or untreated women.