Alteration of the adrenomedullin receptor components gene expression associated with the blood pressure in pregnancy-induced hypertension.

Adrenomedullin (AM) is a potent vasodilator. Pregnancy-induced hypertension (PIH) is a common cause of maternal or fetal mortality. We measured the changes of adrenomedullin receptor components gene expression, receptor activity-modifying protein 2 (RAMP2) and calcitonin receptor-like receptor (CRLR), at feto-maternal tissues in human normotensive pregnant women and pregnancy-induced hypertensive women by Northern blot analysis. Samples of the placenta, uterine muscle, umbilical artery, and fetal membranes were obtained from each patient under informed consent. RAMP2 mRNA significantly decreased in the umbilical artery (54%, P < 0.01) and uterus (53%, P < 0.01) of the patients with PIH. CRLR mRNA also significantly decreased in both tissues of the patients with PIH. On the other hand, the RAMP2 mRNA was significantly increased in the fetal membrane of the patients with PIH. In addition, there was a significant negative correlation between the RAMP2 mRNA levels in the umbilical artery (systolic; r = -0.623, P < 0.01, diastolic; r = -0.552, P < 0.01) and uterine muscle (systolic; r = -0.563, P < 0.01, diastolic; r = -0.553, P< 0.01) and blood pressure. However, there was no correlation between the mRNA level and blood pressure in fetal membrane and placenta, suggesting that there is no close relationship to the pathogenesis in PIH. These findings suggested that the reduced expression of adrenomedullin receptor component in umbilical artery and uterus may have some role in PIH.