A multiparametric analysis of endometrial estrogen and progesterone receptors after the postovulatory administration of mifepristone

A double-blind randomized study was performed in two groups of eight normally cycling patients: group I received 10mg/d of RU486 for 4days from the date of ovulation and group II received a placebo. On day +5, cytosol and endometrial estrogen receptors (ERs), and progesterone receptors (PRs) were analyzed by radioligand binding assay as well as by enzyme immunochemistry. Histologic studies showed that all the endometria of group I were abnormal (luteal insufficiency and/or E/P imbalance). The nuclear PR levels were significantly higher in group I (843±422 fmol/mg) deoxyribonucleic (DNA) compared with 482±232 fmol/mg DNA in group II. Immunohistochemical study showed that ER and PR staining was higher for both glands and stroma in group I (52% and 72% for the respective receptors), compared with the receptor-immunostained surface observed in group II, which was reduced to 40% for ER and to 4% for PR. This study demonstrates that RU486 administered in the immediate postovulatory period blocks normal tissue evolution in the follicular phase as well as the processing of PR.