Localization and distribution of adrenomedullin receptor in the human placenta: changes with gestational age

OBJECTIVE: To examine the distribution and localization of adrenomedullin (AM) receptor (AM-R) in human placenta and fetal membranes to assess any change during pregnancy or with labor. STUDY DESIGN: Immunohistochemistry was performed by the avidin/biotin immunoperoxidase method using an antibody specific to AM-R on intrauterine tissues collected from 7-41 weeks of gestation (n=73). RESULTS: AM-R was localized in the placenta and fetal membranes in all 3 trimesters. The distribution of AM-R in the villous and extravillous trophoblast cells of the placenta and in chorion and decidua cells of the fetal membranes changed with gestational age but not with labor. CONCLUSION: AM is secreted by decidua and trophoblast cells that also possess AM-R, suggesting that placental tissues function in both the synthesis and action of AM. Changes in AM-R in the placenta during pregnancy may reflect changes in AM function throughout gestation.