ESTROGEN AND PROGESTERONE RECEPTORS IN HUMAN DECIDUA AFTER RU486 TREATMENT

Objective: To examine RU486 action on decidua at the level of cellular estrogen receptor (ER) and P receptor (PR). Design: Controlled basic study for contragestion mechanism of mifepristone. Setting: Normal human volunteers in an academic research environment. Patients: Sixty women with 6 to 7 weeks of gestation who voluntarily requested termination of pregnancy were recruited and randomly divided into three groups. Intervention: A single dose of 200 mg RU486 was orally administered to the two treatment groups 12 and 24 hours, respectively, before surgical interruption of pregnancies. Placebo was used for control group. Decidual tissues were collected right after operation. Main Outcome Measure: Immunocytochemical reactions of PR and ER in decidua after RU486 treatment were compared with the control subjects. The differences of the reaction in decidual area with or without trophoblast invasion were noted. Results: RU486 treatment increased PR and ER staining in vessel and stroma of decidua without trophoblast invasion (decidua parietalis) but not in decidua with trophoblast invasion (decidua capsularis or basalis). Chi-squared analysis indicated a significant increase in the number of ER-positive samples after RU486 treatment. Conclusion: The decidua parietalis was the primary target site of RU486. The lack of RU486 effect on decidua capsularis implied that trophoblast invasion prevented against antiprogestin impact.