Detection of adrenomedullin, a hypotensive peptide, in amniotic fluid and fetal membranes

OBJECTIVE: Our purpose was to determine whether adrenomedullin, a multifunctional regulatory peptide involved in blood flow regulation and growth stimulation and with antimicrobial activity, was a component of amniotic fluid from second-trimester human fetus and to determine the source of this peptide. STUDY DESIGN: A prospective descriptive study was performed on 134 patients undergoing amniocentesis after genetic counseling, ultrasonography, and infomed consent. Adrenomedullin expression was determined by immunocytochemical analysis, Western blot analysis, reverse transcriptase-polymerase chain reaction, and in situ reverse transcriptase-polymerase chain reaction in fetal membranes and with radioimmunoassay in amniotic fluid. RESULTS: Radioimmunoassay of the 134 amniotic fluid specimens revealed adrenomedullin-like immunoreactivity in all of them, ranging in concentration from 10 to 300 fmol/25 mu l (170 +/- 62 fmol/25 mu l. Immunocytochemical analysis, Western blot analysis, reverse transcriptase-polymerase chain reaction, and in situ reverse transcriptase-polymerase chain reaction further established the expression of adrenomedullin protein and messenger ribonucleic acid in fetal amniotic membranes, suggesting that this organ is the source of amniotic adrenomedullin. CONCLUSIONS: Our results clearly demonstrate the presence of adrenomedullin in second-trimester human amniotic fluid and adrenomedullin messenger ribonucleic acid and protein in amniotic membranes, suggesting that adrenomedullin is a hormone involved in the maintenance of normal pregnancy. Further studies with these molecular tools are in progress to determine the precise role of this hormone and whether adrenomedullin plays a role in the pathogenesis of various disorders of pregnancy.