title: Inhibin-B and pro-alphaC-containing inhibins in amniotic fluid from chromosomally normal and Down syndrome pregnancies.
abstract: In second-trimester Down syndrome pregnancies, levels of inhibin-A (the alpha-betaA dimer) in maternal serum and amniotic fluid (AF) are significantly higher and lower than in normal pregnancy, respectively. Since AF also contains inhibin-B (the alpha-betaB dimer) and precursor inhibins, we have examined whether the secretion of these inhibin isoforms may also be altered in association with Down syndrome. AF from 45 Down syndrome and 150 chromosomally normal pregnancies between 16 and 19 weeks' gestation were analysed, blinded to whether the sample was from a Down syndrome or a normal pregnancy. The median (10th-90th percentiles) inhibin-B level in the control pregnancies increased from 310.0 (80.8-1112.5) pg/ml at 16 weeks to 459.5 (193.7-1386.8) pg/ml at 19 weeks' gestation. The corresponding figures for precursor inhibins (pro-alphaC inhibins) were 541.8 (206.9-1322.8) pg/ml at 16 weeks and 1391.8 (433.3-2652.6) pg/ml at 19 weeks. Expressed as multiples of the median (MOM), the levels of inhibin-B and pro-alphaC inhibins in the Down syndrome samples were 0.85 and 0.79, respectively. Neither was significantly different from the controls. These data suggest that, of the three inhibin subunits, abnormal production or secretion of the inhibin betaA-subunit may underlie the decreased inhibin-A levels previously observed in Down syndrome. Confirmation of this by quantitative assessment of the inhibin subunit messenger ribonucleic acids would now be useful.
authors.affiliation: Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia. Euan.M.Wallace@med.monash.edu.au
authors.forename: E M
authors.initials: EM
authors.lastname: Wallace
authors.forename: J A
authors.initials: JA
authors.lastname: Crossley
authors.forename: S C
authors.initials: SC
authors.lastname: Riley
authors.forename: C
authors.initials: C
authors.lastname: Balfour
authors.forename: N P
authors.initials: NP
authors.lastname: Groome
authors.forename: D A
authors.initials: DA
authors.lastname: Aitken
mesh_terms: D000649:Amniocentesis; D000653:Amniotic Fluid / Q000737:chemistry*; D015331:Cohort Studies; D004314:Down Syndrome / Q000196:embryology* / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007265:Inhibins / Q000032:analysis* / Q000378:metabolism; D010455:Peptides / Q000032:analysis / Q000378:metabolism; D011247:Pregnancy; D011446:Prospective Studies; D029584:Prostatic Secretory Proteins; D011498:Protein Precursors / Q000032:analysis / Q000378:metabolism; D012016:Reference Values
chemical_list: D010455:Peptides; D029584:Prostatic Secretory Proteins; D011498:Protein Precursors; C043076:beta-microseminoprotein; C094377:inhibin-alpha subunit; C095971:inhibin-alpha subunit precursor; D007265:Inhibins