EFFECTS OF A SINGLE POSTOVULATORY DOSE OF RU486 ON ENDOMETRIAL MATURATION IN THE IMPLANTATION PHASE

The effect of a single post-ovulatory dose of RU486 on endometrial maturation was studied in the implantation phase. A total of 11 healthy women were followed for one control and one or two treatment cycles. In treatment cycles, a dose of 200 or 400 mg RU486 was administered on day luteinizing hormone (LH)+2. In both control and treatment cycles, an endometrial biopsy was obtained on LH+6 to 1,11+8. These biopsies were assessed by morphometric and immunohistochemical analyses. The treatment with RU486 did not disturb the normal menstrual rhythm but caused a significant inhibition in the endometrial development, Glandular progesterone receptor staining was significantly more pronounced after RU486 treatment, while there was a reduction in the Dolichos biflorus agglutinin lectin binding, indicating inhibition of the normal secretory transformation of the endometrium. It is likely that these effects on endometrial development and secretory activity represent the basis of the contraceptive effect of post-ovulatory RU486 treatment.