Barbara Villaccio

Adrenomedullin, a New Vasoactive Peptide, Is Increased in Preeclampsia

Adrenomedullin is a novel peptide that elicits a long-lasting vasorelaxant activity. Recently, we found high concentrations of adrenomedullin in maternal and umbilical cord plasma and in amniotic fluid in full-term human pregnancy, indicating a role of this peptide during gestation. To investigate the possibility that adrenomedullin is involved in the pathophysiology of preeclampsia, we measured its concentration in maternal and fetoplacental compartments. We studied 12 normotensive nonpregnant women, 13 hypertensive nonpregnant subjects, 29 patients with preeclampsia, and 30 normotensive pregnant women. In all patients, plasma was collected from the cubital vein, and amniotic fluid samples were obtained by transabdominal amniocentesis or at elective cesarean section. Plasma samples from umbilical vein and placental tissues were collected at delivery. Adrenomedullin was assayed on plasma and amniotic fluid samples using a specific radioimmunoassay, and its localization and distribution on placental sections was determined by immunohistochemistry. Adrenomedullin concentrations were higher in hypertensive than in normotensive nonpregnant patients. Pregnant women had higher adrenomedullin levels than nonpregnant subjects, although maternal plasma adrenomedullin concentrations did not differ between normal pregnant and preeclamptic women. Preeclamptic patients showed higher concentrations (P<0.01) than normotensive pregnant women of adrenomedullin in amniotic fluid (252+/-29 versus 112+/-10 fmol/ micromol creatinine) and umbilical vein plasma (18.1+/-2.1 versus 8. 5+/-1.1 fmol/mL). Increased local production of adrenomedullin is associated with preeclampsia. The fetus seems to be responsible for the higher levels of this hormone. Increased adrenomedullin concentrations may be necessary to maintain placental vascular resistance and/or fetal circulation at a physiological level.

Immunoreactive adrenomedullin in human fetoplacental tissues

OBJECTIVE Adrenomedullin is increased in maternal plasma in pregnancy and has been found in very high concentrations in amniotic fluid and umbilical plasma. To identify adrenomedullin-producing tissue in pregnancy we measured adrenomedullin concentration and distribution in fetoplacental tissues. STUDY DESIGN By use of a specific radioimmunoassay we determined the concentrations of adrenomedullin and, by immunohistochemical studies, its localization and distribution in fetal membranes and placentas collected at elective cesarean section from 11 healthy pregnant women at term. RESULTS The content of adrenomedullin in placentas (117.7 +/- 7.8 pg/mg wet tissue) and fetal membranes (168.7 +/- 2.3 pg/mg wet tissue) was similar to the adrenomedullin concentration in adrenal medulla (157.3 +/- 4.4 pg/mg wet tissue). Adrenomedullin staining appears to be greater in fetal membranes than in placentas and was localized in amnion and trophoblast cells. In term placentas positive staining was detected predominantly in extravillous trophoblast cells, although a few syncytiotrophoblast cells and endothelial cells of primary villi stained for adrenomedullin. CONCLUSION This study provides evidence that is consistent with fetoplacental tissues as a site of synthesis or action of adrenomedullin during pregnancy.

Nitric oxide in preeclampsia: lack of evidence for decreased production

The purpose of our study was to determine the involvement of the L-arginine-NO system in preeclampsia. We studied 26 patients with preeclampsia and 27 normotensive pregnancies. Maternal and cord plasma, urine and amniotic fluid were assayed for nitric oxide metabolites (nitrite and nitrate) using the Griess reaction. Sections of placenta and fetal membranes were immunostained with polyclonal anti-endothelial and anti-neuronal nitric oxide synthase antibodies. The concentration of nitrate in the amniotic fluid of preeclamptic patients (median 10.3 mumol/mg creatinine) was significantly higher (P < 0.001) than in the normotensive group (5.6 mumol/mg creatinine). Nitrate concentrations in maternal and cord plasma and in urine were similar in the two groups. Endothelial cells of the villi of preeclamptic placentas showed a higher positivity in endothelial nitric oxide synthase immunostaining with respect to normotensive controls. Our results indicate that feto-placental NO production is not reduced in preeclampsia. In contrast, the increased concentrations of NO metabolites in amniotic fluid and the positive immunostaining of endothelial nitric oxide synthase in the placental villi suggest that the placental L-arginine-NO system is up-regulated in preeclampsia.

Amniotic fluid nitric oxide metabolite levels and nitric oxide synthase localization in feto-placental tissues are modified in association with human labor

Nitric oxide (NO) has a relaxant effect on uterine smooth muscle and may be implicated in maintaining uterine quiescence during pregnancy. In order to investigate the role of nitric oxide in human parturition, we have measured NO metabolite levels in maternal and fetal compartments in association with labor, both at term and preterm. We have also examined the localization and distribution of NO synthase (NOS) isoforms in placentas and fetal membranes after term and preterm delivery by means of immunohistochemistry. Although no differences were present in maternal and fetal blood and in maternal urine among groups, we found that NO metabolite concentrations were higher in amniotic fluid collected from women in labor than in non-laboring patients, both at term (15.4+/-1.6 vs. 6.8+/-0.6 microM/mg creatinine) and preterm (16.7+/-2.0 vs. 7.0+/-0.8 microM/mg creatinine). Ir-bNOS staining appeared to be decreased in fetal membranes collected after spontaneous labor at term and preterm. In contrast, a stronger staining for iNOS was detected in trophoblast cells of fetal membranes from women in labor than in those from non-laboring women. We suggest that NOS isoenzymes in fetal placental tissues are differently regulated and might play different roles during pregnancy.

Immunohistochemical Localization of Adrenomedullin in Fetal and Neonatal Lung

Adrenomedullin is a potent hypotensive peptide that has been demonstrated to increase pulmonary blood flow in fetal sheep. To examine whether adrenomedullin plays a role in the transitional changes of human pulmonary blood flow at birth, we have evaluated, by immunohistochemistry, its presence and distribution in fetal lung during gestation using a polyclonal antibody directed toward human adrenomedullin 1-52. We collected lung specimen from abortive fetuses (n = 6), preterm neonates (n = 4), and term infants (n = 3). Two adult lung specimen were used as controls. Immunoreactive adrenomedullin was detected in fetal lung collected as early as at 18 wk of gestation and in all tissues throughout gestation. Adrenomedullin was localized predominantly in the epithelial cells of bronchi, with an apical distribution. Endothelial cells also stained for adrenomedullin. The intensity of staining and the percentage of positive bronchial epithelial cells increased as gestation progressed; but staining for adrenomedullin was absent in tissues collected after breathing and in the adult controls. These findings indicate that adrenomedullin may play an important role in respiratory homeostasis at birth. Moreover, the immunohistochemical expression of AM in the late organogenetic period and its increasing staining during fetal lung development may suggest a possible role in the mechanisms of fetal lung differentiation and/or maturation.

Follicular fluid adrenomedullin concentrations in spontaneous and stimulated cycles: relationship to ovarian function and endothelin-1 and nitric oxide

The objective of this study was to determine concentration of adrenomedullin (AM) in follicular fluid and whether a correlation exists between AM and nitric oxide (NO) or endothelin-1 (ET-1) levels in follicular fluid, serum 17beta-estradiol or other parameters of ovarian function in spontaneous and gonadotrophin stimulated ovarian cycles. Follicular fluid samples were obtained at oocyte retrieval from 50 women who underwent an in vitro fertilization (IVF) program: 40 undergoing ovarian hyperstimulation with recombinant FSH and 10 had spontaneous ovarian cycles. AM, ET-1, and NO were detected in all of the follicular fluid samples and their concentrations were similar in spontaneous and stimulated cycles. In patients undergoing ovarian stimulation, follicular fluid AM levels correlated with serum 17beta-estradiol concentration. No correlation was found between follicular AM concentration and parameters of ovarian function. Similarly, no relationship was observed between ET-1, NO, and AM follicular fluid concentrations in either spontaneous or stimulated cycles. This study suggests a possible regulatory effect of the sexual hormones on AM production by the ovary during the ovulatory process. The site of AM secretion and its function (if any), however, remain to be established.

Amniotic fluid concentrations of adrenomedullin in preterm labor

OBJECTIVE To determine whether adrenomedullin levels in amniotic fluid were associated with preterm labor. METHODS We measured immunoreactive adrenomedullin in amniotic fluid collected by amniocentesis from 36 women with clinical diagnosis of preterm labor or preterm premature rupture of membranes (PROM) and from 18 normal pregnant women. RESULTS Amniotic fluid from cases of PROM and failure to respond to tocolysis were associated significantly with higher amniotic fluid adrenomedullin concentrations (177.0 +/- 22.5 pg/mL and 182.7 +/- 22.0 pg/mL, respectively, P < .01) than that from uncomplicated pregnancies (101.2 +/- 28.1 pg/mL) or preterm labor responsive to tocolysis (102.3 +/- 26.8 pg/mL). CONCLUSION Amniotic fluid adrenomedullin is higher than normal in cases of PROM and preterm labor unresponsive to tocolysis, perhaps indicating enhanced synthesis from placenta or fetal membranes being stimulated by bacterial products.