Localization and expression of oxytocin receptor and its messenger ribonucleic acid in peri-implantation phase human endometrium during control and clomiphene-treated cycles

OBJECTIVES: This study was undertaken to determine expression levels of oxytocin receptor and its gene in peri-implantation phase human endometrium during clomiphene-treated cycles compared with control cycles. STUDY DESIGN: Oxytocin receptor and its messenger ribonucleic acid in peri-implantation phase endometrium during control and clomiphene-treated (50 mg days 5 to 9) cycles of 5 healthy fertile women were determined by immunohistochemical methods, Western blot analysis with monoclonal antibody against amino acids 20 through 40 of the extracellular N-terminal human oxytocin receptor, and reverse transcription-polymerase chain reaction with oligonucleotide primers to amplify the 391-base pair fragment of the oxytocin receptor gene. RESULTS: Oxytocin receptor and its messenger ribonucleic acid were expressed in human peri-implantation phase endometrial samples from both control and clomiphene-treated cycles. The receptor was localized predominantly in the epithelial cells and glands, with little or none detected in the stroma. Oxytocin receptor protein was separated out as a single 70-kd band by Western blot analysis; its relative abundance was significantly reduced during clomiphene-treated cycles. The messenger ribonucleic acid was detected in all endometrium during control and clomiphene-treated cycles, with greater expression during control cycles. CONCLUSIONS: The expressions of oxytocin receptor and its gene in luteal phase human endometrium suggest a functional relevance in modulation of biochemical changes for implantation.