title: Role of the L-arginine nitric oxide pathway in hypoxic fetoplacental vasoconstriction.
abstract: The role of nitric oxide in hypoxic fetoplacental vasoconstriction (HFPV) was investigated using dually perfused human placental cotyledons. Standard medium (Earle's salt solution with added dextran and L-arginine) was equilibrated with 95 per cent O2 and 5 per cent CO2 (maternal side) and 94 per cent N2 and 6 per cent CO2 (fetal side). Part 1 consisted of perfusion for 1 h, then maternal perfusate equilibrated with a 95 per cent N2 and 5 per cent CO2 for 20 min (hypoxia), and then the original perfusion conditions resumed for 40 min. In part 2, this sequence was repeated with standard medium alone (n = 6), or with added N-nitro-L-arginine methyl ester (L-NAME) (n = 6), or L-NAME and nitroglycerin (n = 6). When standard medium was used throughout, basal fetal perfusion pressure (30 +/- 2 mmHg) and the hypoxia-induced increase in perfusion pressure (18 +/- 1 mmHg) did not change significantly between parts 1 and 2. L-NAME increased basal perfusion pressure from 33 +/- 3 to 56 +/- 2 mmHg whereas perfusion pressure remained unchanged with L-NAME and nitroglycerin or nitroglycerin alone. The hypoxic vasoconstriction observed during part 1 in the L-NAME (14 +/- 3 mmHg) and the L-NAME with nitroglycerin groups (18 +/- 2 mmHg) was abolished during part 2 (to - 4 +/- 1 and 0.4 +/- 0.5 mmHg, respectively) whereas nitroglycerin alone significantly blunted the response (21 +/- 3 to 6 +/- 1 mmHg). Results suggest that a reduction in basal NO release mediates hypoxic fetoplacental vasoconstriction in the perfused human placental cotyledon in vitro.
authors.affiliation: Department of Obstetrics and Gynecology, University of Toronto, Ontario, Canada.
authors.forename: B M
authors.initials: BM
authors.lastname: Byrne
authors.forename: R B
authors.initials: RB
authors.lastname: Howard
authors.forename: R J
authors.initials: RJ
authors.lastname: Morrow
authors.forename: K J
authors.initials: KJ
authors.lastname: Whiteley
authors.forename: S L
authors.initials: SL
authors.lastname: Adamson
mesh_terms: D000328:Adult; D001120:Arginine / Q000502:physiology*; D001784:Blood Gas Analysis; D004338:Drug Combinations; D005260:Female; D005311:Fetal Hypoxia / Q000503:physiopathology*; D006801:Humans; D066298:In Vitro Techniques; D008431:Maternal-Fetal Exchange / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009569:Nitric Oxide / Q000502:physiology*; D005996:Nitroglycerin / Q000008:administration & dosage; D010477:Perfusion; D010920:Placenta / Q000098:blood supply* / Q000378:metabolism; D011247:Pregnancy; D014661:Vasoconstriction / Q000502:physiology*
chemical_list: D004338:Drug Combinations; D009569:Nitric Oxide; D001120:Arginine; D005996:Nitroglycerin; D019331:NG-Nitroarginine Methyl Ester