Change of Adrenomedullin Concentrations in Plasma and Amniotic Fluid, and Human Placental Adrenomedullin Expression with Advancing Gestation

Abstract

In order to characterize the expression of adrenomedullin during pregnancy, we measured the mature and total concentrations in maternal plasma and amniotic fluid, and examined its expression in fetoplacental tissues. Plasma samples were obtained from 13 normal normotensive non-pregnant women and 14 normal normotensive post partum women. Maternal plasma and amniotic fluid samples were obtained from 37 normal pregnant women (10 in the first trimester, 13 in the second trimester and 14 in the third trimester). Fetoplacental tissues were obtained from first and third-trimester pregnancies. Mature and total adrenomedullin concentrations in plasma and amniotic fluid were determined by using specific radioimmunoassay. The distribution and expression of adrenomedullin were determined using immunohistochemistry, reverse-transcriptase polymerase chain reaction, and in situ hybridization. Plasma total adrenomedullin concentrations were increasing with advancing gestation. The mature/total adrenomedullin ratio in the second trimester was the highest during pregnancy. Mature and total adrenomedullin concentrations in the amniotic fluid were significantly higher than those in the maternal plasma throughout gestation (P< 0.05). Mature adrenomedullin concentrations and the mature/total adrenomedullin ratio in the amniotic fluid increased with advancing gestation. There was a significant linear correlation between amniotic fluid and maternal plasma mature/total adrenomedullin ratio in the first or second trimester of pregnancy. Adrenomedullin mRNA was identified in the amniotic membrane and chorionic villi, and within the endothelial layers of villous blood vessels. These results suggest that the mature/total adrenomedullin ratio is modified in maternal plasma and amniotic fluid with advancing gestation.