Adrenomedullin and atrial natriuretic peptide concentrations in normal pregnancy and pre-eclampsia

Adrenomedullin (AM) is a peptide that elicits a long-lasting vasorelaxant a ctivity, while atrial natriuretic peptide (ANP) has also been shown to be a potent vasodilatory agent. To clarify the possible role of AM and ANP in t he physiology of pregnancy and pathophysiology of pre-eclampsia, we measure d plasma concentrations of these peptides in non-pregnant women, normal pre gnant women and women with preeclampsia. A gradual increase in plasma AM wa s observed as pregnancy progressed. The plasma AM concentrations during the second trimester (12.7 +/- 1.4 fmol/ml) were significantly elevated, in co mparison with the non-pregnant follicular phase (6.4 +/- 0.61 fmol/ml), lut eal phase (6.0 +/- 0.49 fmol/ml), and the first trimester (6.5 +/- 0.8 fmol /ml). The plasma AM concentrations of the third trimester (21.5 +/- 1.4 fmo l/ml) were significantly elevated when compared with those of the second tr imester (P < 0.05). Northern blot analysis confirmed the expression of the AM mRNA transcript (1.6 kb) in third trimester placentas. In comparison wit h those observed at term (25.3 +/- 4.5 fmol/ml), the plasma concentrations were significantly reduced postpartum (6.4 +/- 0.6 fmol/ml). In the third t rimester, plasma AM concentrations did not differ significantly between wom en with pre-eclampsia (17.2 +/- 2.3 fmol/ml) and normal pregnant women. In contrast, the plasma ANP concentrations in pre-eclampsia (39.5 +/- 7.1 pg/m l) were significantly elevated when compared with those of the normal third trimester (14.4 +/- 1.4 pg/ml) (P < 0.05). ANP concentrations were reasona bly constant throughout the pregnancy.