THE EFFECT OF A SINGLE-DOSE OF MIFEPRISTONE (RU486) ON THE FINE-STRUCTURE OF THE HUMAN ENDOMETRIUM DURING THE EARLY LUTEAL-PHASE

This study examined the fine structure of the human endometrial glandu lar epithelium after the administration of a single dose of RU486 (mif epristone), given in the early luteal phase, The drug was administered on days 2, 3, 5 and 6 after the luteinizing hormone peak (LH + 0), Bi opsies were performed on days LH + 5, 6, 8 and 9, These were compared with control biopsies taken on corresponding days, Qualitatively, the main cytological effect of the RU486 was on the secretory apparatus an d on the polarity of the cell, The formation of the nuclear channel sy stem was also affected by the drug, A two-way analysis of variance on cell and nuclear volume data revealed no significant effect of day of biopsy, condition or interaction, Mitochondrial volume and secretory a pparatus volume data revealed a significant effect of day of biopsy an d interaction term; mitochondrial volume at LH + 5 was 95.9 +/- 25.3 m u m(3) (mean a SD) for control and 57.7 +/- 31.9 mu m(3) for RU486-tre ated epithelium. The volume of the secretory apparatus in the treated group was smaller on days LH+5 and 6 (14.6 +/- 4.2 mu m(3), 6.41 +/- m u m(3)) when compared to daymatched control biopsies (35.9 +/- 10.5 mu m(3), 41.7 +/- 26.4 mu m(3)). RU486 administration in the early lutea l phase disrupted the secretory activity of the cells, These findings provide an insight into the cellular mechanisms of progesterone recept or blockade in the peri-implantation period.