title: Myometrial nitric oxide synthase messenger ribonucleic acid expression does not change throughout gestation or with the onset of labor.
abstract: OBJECTIVE
  The purposes of this study were to examine expression of nitric oxide synthase isoforms in human myometrium and to determine any changes in expression with gestational age and with the onset of labor at term.
  
  
  METHODS
  Myometrial samples were collected from patients undergoing cesarean delivery at term before and after the onset of labor (n = 17) and throughout gestation (n = 13). Expressions of inducible, calcium-independent nitric oxide synthase and constitutive, calcium-dependent endothelial nitric oxide synthase were determined by semiquantitative reverse transcriptase-polymerase chain reaction.
  
  
  RESULTS
  Messenger ribonucleic acid for inducible, calcium-independent nitric oxide synthase and constitutive, calcium-dependent endothelial nitric oxide synthase is expressed in human myometrium at term and throughout the second and third trimesters. Levels of messenger ribonucleic acid for both inducible, calcium-independent nitric oxide synthase and constitutive, calcium-dependent endothelial nitric oxide synthase do not change with either gestational age or the onset of labor.
  
  
  CONCLUSIONS
  Changes in myometrial nitric oxide synthase expression and thus of levels of endogenous nitric oxide are unlikely to be directly involved in myometrial quiescence or the onset of human parturition.
authors.affiliation: Division of Paediatrics, Imperial College School of Medicine, Queen Charlotte's and Chelsea Hospital, London, United Kingdom.
authors.forename: W J
authors.initials: WJ
authors.lastname: Dennes
authors.forename: D M
authors.initials: DM
authors.lastname: Slater
authors.forename: L
authors.initials: L
authors.lastname: Poston
authors.forename: P R
authors.initials: PR
authors.lastname: Bennett
mesh_terms: D002118:Calcium / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D005865:Gestational Age; D006801:Humans; D007743:Labor, Obstetric / Q000502:physiology*; D009215:Myometrium / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis*; D020133:Reverse Transcriptase Polymerase Chain Reaction