title: Intracrine control of estrogen action in human gestational tissues at parturition.
abstract: OBJECTIVE
  We examined whether estrogen action in human parturition is regulated by an intracrine mechanism mediated by target tissue expression of specific 17beta-hydroxysteroid dehydrogenase (17betaHSD) isozymes that interconvert estrone (E1) and estradiol (E2), such that the onset of labor is associated with an increase in local E2 bioavailability.
  
  
  METHODS
  The extent of 17betaHSD-1, -2, -3, -4, -5, and -7 expression (measured by quantitative reverse transcriptase polymerase chain reaction) and the capacity to interconvert E1 and E2 were compared in amnion, chorion, placenta, decidua, and myometrium obtained from women at term before (n = 6) and after (n = 6) the onset of labor.
  
  
  RESULTS
  In chorion, abundance of 17betaHSD-1 (converts E1 to E2) mRNA decreased 2.7-fold (P <.05) in association with labor onset. In myometrium, 17betaHSD-1 and 17betaHSD-4 (converts E2 to E1) mRNAs increased two-fold and five-fold, respectively, with the onset of labor (P <.05 for each). No other statistically significant labor-associated change in 17betaHSD expression was observed. In chorion, 17betaHSD oxidative (E2 to E1) and reductive (E1 to E2) activities and the net E2 synthetic capacity increased with labor. In decidua, both activities decreased with the onset of labor, but there was no change in net E2 synthetic capacity. The capacity to interconvert E1 and E2 did not change in the other tissues.
  
  
  CONCLUSIONS
  The increase in E2 synthetic capacity in the chorion might contribute to an increase in local estrogen bioactivity in association with the onset of labor. However, it cannot be explained by changes in 17betaHSD isozyme expression and is unlikely to account for the increased estrogen action at parturition. These data show that intracrine mechanisms based on 17betaHSD isozyme expression play a minor role, if any, in controlling estrogen action in gestational tissues during human parturition.
authors.affiliation: Mothers and Babies Research Centre, University of Newcastle and John Hunter Hospital, Newcastle, New South Wales, Australia.
authors.forename: Gemma
authors.initials: G
authors.lastname: Madsen
authors.forename: Tamas
authors.initials: T
authors.lastname: Zakar
authors.forename: Ursula
authors.initials: U
authors.lastname: Manuelpillai
authors.forename: Euan
authors.initials: E
authors.lastname: Wallace
authors.forename: Kenneth
authors.initials: K
authors.lastname: Kwek
authors.forename: George S H
authors.initials: GS
authors.lastname: Yeo
authors.forename: Roger
authors.initials: R
authors.lastname: Smith
authors.forename: Sam
authors.initials: S
authors.lastname: Mesiano
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D002823:Chorion / Q000201:enzymology; D003656:Decidua / Q000201:enzymology; D004958:Estradiol / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology*; D004970:Estrone / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007743:Labor, Obstetric; D009215:Myometrium / Q000201:enzymology; D036801:Parturition; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D004967:Estrogens; D007527:Isoenzymes; D012333:RNA, Messenger; D004970:Estrone; D004958:Estradiol; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase