Localization of messenger ribonucleic acid for adrenomedullin and adrenomedullin receptor in the human placenta in normal pregnancies and pregnanciescomplicated by oligohydramnios

OBJECTIVE: The purpose of this study was to identify the placental expressi on of adrenomedullin and adrenomedullin receptor messenger ribonucleic acid and compare them between placentas from pregnancies associated with oligoh ydramnios as a result of uteroplacental insufficiency and placentas from no rmal pregnancies. STUDY DESIGN: Total ribonucleic acid was extracted from the amnion, chorion , cotyledon, umbilical vein, and umbilical artery in 5 normal placentas and 3 placentas from pregnancies complicated by oligohydramnios. A cell line k nown to express messenger ribonucleic acid of adrenomedullin and its recept or was used to optimize the polymerase chain reaction and served as a posit ive control preparation in all experiments. Semiquantitative reverse transc riptase-polymerase chain reaction results for adrenomedullin and adrenomedu llin receptor were compared between tissues as densitometric ratios of adre nomedullin or adrenomedullin receptor messenger ribonucleic acid to beta (2 )-microglobulin messenger ribonucleic acid. Results were analyzed with a Kr uskal-Wallis 1-way analysis of variance. Immunohistochemical staining with an antibody to human adrenomedullin was used to localize adrenomedullin in all tissue types. RESULTS: Messenger ribonucleic acid sequences for adrenomedullin and adreno medullin receptor genes were identified in ail tested placental tissue comp onents. Within the normal placentas the expressions of adrenomedullin and a drenomedullin receptor messenger ribonucleic acid sequences did not differ statistically between the tissue components. Within placentas from patients with oligohydramnios the expressions of adrenomedullin and adrenomedullin receptor messenger ribonucleic acid did not differ statistically between th e tissue components. When normal placentas were compared with placentas fro m pregnancies complicated by oligohydramnios, however, a 5-fold increase in adrenomedullin messenger ribonucleic acid and a 3-fold increase in adrenom edullin receptor messenger ribonucleic acid were seen in placentas from pat ients with oligohydramnios. Adrenomedullin immunoreactivity was present in all tissues studied. CONCLUSION: The expression of messenger ribonucleic acid for both adrenomed ullin and its receptor in these tissue components implies that placental ti ssues function in both synthesis and action of adrenomedullin. The increase d adrenomedullin messenger ribonucleic acid expression in the umbilical art ery and the elevated adrenomedullin receptor messenger ribonucleic acid exp ression in the cotyledons of placentas from patients with oligohydramnios m ay represent a local fetoplacental physiologic adaptive response to vascula r compromise.