Objective: To investigate the effects of the antiprogestin mifepristone on expression of endothelial (eNOS) nitric oxide synthase in human endometrium during the implantation phase.
Design: Prospective clinical study.
Setting: Teaching university hospital.
Patient(s): Endometrial samples were obtained from nine healthy women with proven fertility.
Intervention(s): One control and one treatment cycle were performed. Treatment with 200 mg of mifepristone was administered on LH day 2. Endometrial biopsy specimens were obtained on LH day 6 to 8.
Main outcome measure(s): Expression of eNOS was identified by using immunohistochemistry and Western blot assay, and messenger RNA levels were determined with semiquantitative reverse transcription polymerase chain reaction.
Result(s): Endothelial nitric oxide synthase was detected in vascular endothelium and glandular epithelium in the endometrium. Treatment with mifepristone significantly decreased eNOS expression in the endometrial glandular epithelium but did not affect endothelial eNOS.
Conclusion(s): Mifepristone has differential effects on eNOS expression in the epithelium and endothelium in the human endometrium at the time of implantation. The results support a role of epithelial eNOS in human endometrial receptivity.