title: Effect of endothelium-derived relaxing factor inhibition on the umbilical-placental circulation in fetal lambs in utero.
abstract: OBJECTIVE
  The purpose of this study was to examine whether basal endothelium-derived relaxing factor release contributes to regulation of resting umbilical-placental vascular resistance.
  
  
  METHODS
  Because N omega-nitro-L-arginine selectively inhibits the synthesis of nitric oxide, a major endothelium-derived relaxing factor, we investigated the effects of N omega-nitro-L-arginine on umbilical-placental vascular resistance in 10 fetal lambs in utero. We inserted catheters and fitted an umbilical artery electromagnetic flow transducer around the common umbilical artery to measure umbilical blood flow and catheterized the left umbilical arterial hypogastric branch to allow selective umbilical-placental infusion (60 minutes) of pH-matched saline solution (control) or N omega-nitro-L-arginine.
  
  
  RESULTS
  In seven normal fetal lambs, N omega-nitro-L-arginine increased umbilical-placental vascular resistance and arterial pressures and decreased umbilical blood flow (p less than 0.05); percentage changes from baseline were 50.8% +/- 18.3%, 40.3% +/- 8.1%, and -9.9% +/- 6.4%, respectively. In three mildly asphyxiated (compromised) fetuses, these changes were 101.4% +/- 28.7%, 31.2% +/- 4.8%, and -37.9% +/- 12.0%.
  
  
  CONCLUSIONS
  These data support the hypothesis that the basal endothelium-derived relaxing factor release plays a role in regulating resting umbilical-placental vascular resistance.
authors.affiliation: Department of Pediatrics, Tri-Service General Hospital, Taipei, Taiwan.
authors.forename: J K
authors.initials: JK
authors.lastname: Chang
authors.forename: C
authors.initials: C
authors.lastname: Roman
authors.forename: M A
authors.initials: MA
authors.lastname: Heymann
mesh_terms: D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D012756:Sheep; D014470:Umbilical Cord / Q000098:blood supply*; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine