Effect of mifepristone on estrogen and progesterone receptors in human endometrial and endometriotic cells in vitro.

Objective: To investigate the expressions of estrogen (E) receptor and progesterone (P) receptor in human eutopic and ectopic endometrium and the effect of mifepristone (RU486) on them.

Design: Prospective study.

Setting: University hospital.

Patient(s): Twenty-two patients with ovarian endometriosis and 13 patients with uterine leiomyoma were recruited.

Intervention(s): Samples of ovarian endometrioma cyst tissue and endometrium were obtained from the 22 patients. A sample of endometrium was obtained from the 13 patients.

Main Outcome Measure(s): Expressions of E and P receptors were determined using immunocytochemical method.

Result(s): P receptor expression in endometrial epithelial cells with endometriosis was significantly higher than that without endometriosis in the early secretory phase. Estrogen receptor and epithelial P receptor expressions in endometriotic cells were significantly lower than those of endometrial cells during the proliferative phase, similar with the latter during the early secretory phase and significantly higher during the late secretory phase. RU486 down-regulated the expressions of E and P receptors in both the eutopic and the ectopic endometrial cells, and in some cases this down-regulating effect was more apparent when the concentration of RU486 was higher.

Conclusion(s): Different steroid receptor expressions indicate different hormonal regulation between endometriotic and endometrial cells. The down-regulating effect on E and P receptors may be one of the therapeutic mechanisms of RU486 on endometriosis.