title: Interplay of endothelial and inducible nitric oxide synthases modulates the vascular response to ischaemia-reperfusion in the rabbit lung.
abstract: OBJECTIVE
  Lung ischaemia-reperfusion induces nitric oxide synthesis and reactive nitrogen species, decreasing nitric oxide bioavailability. We hypothesized that in the ventilated lung, this process begins during ischaemia and intensifies with reperfusion, contributing to ischaemia-reperfusion-induced pulmonary vasoconstriction. The aim was to determine whether ischaemia-reperfusion alters inducible and endothelial nitric oxide synthase expression/activity, reactive nitrogen species generation, and nitric oxide bioavailability, potentially affecting pulmonary perfusion.
  
  
  METHODS
  Ischaemia-reperfusion was induced for various times in anesthetized rabbits with ventilated lungs by reversibly occluding the right pulmonary artery and initiating reperfusion. Nitric oxide synthase activity/expression and phosphorylation, reactive nitrogen species generation and total nitrate/nitrite were determined in lung tissue.
  
  
  RESULTS
  Inducible nitric oxide synthase expression and activity, and reactive nitrogen species formation coincided with increased pulmonary vascular resistance during reperfusion and increased with ischaemia duration, further increasing after 2-h reperfusion. Total nitrate/nitrite also increased with ischaemia but decreased after 2-h reperfusion. Pre-treatment with an inducible nitric oxide synthase inhibitor (1400W; Cayman Chemical Company, Ann Arbor, MI, USA) attenuated inducible nitric oxide synthase activity, reactive nitrogen species generation and pulmonary vascular resistance, but did not affect total nitrate/nitrite. Endothelial nitric oxide synthase expression was unchanged by ischaemia-reperfusion; however, its phosphorylation on serine 1177 and dephosphorylation on threonine 495 was uncoupled, suggesting decreased endothelial nitric oxide synthase activity. 1400W prevented uncoupling of endothelial nitric oxide synthase phosphorylation, maintaining its activity during reperfusion.
  
  
  CONCLUSIONS
  Ischaemia-reperfusion up-regulates inducible nitric oxide synthesis and/activity, which coincides with reduced endothelial nitric oxide synthase activity as suggested by its uncoupling and may contribute to ischaemia-reperfusion-induced pulmonary vasoconstriction.
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, University of Louisville, KY, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Sedoris
authors.forename: E
authors.initials: E
authors.lastname: Gozal
authors.forename: A V
authors.initials: AV
authors.lastname: Ovechkin
authors.forename: A R
authors.initials: AR
authors.lastname: Theile
authors.forename: A M
authors.initials: AM
authors.lastname: Roberts
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008168:Lung / Q000098:blood supply*; D019255:NADPH Oxidases / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D010766:Phosphorylation; D011651:Pulmonary Artery / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D011652:Pulmonary Circulation; D011817:Rabbits; D026361:Reactive Nitrogen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000201:enzymology* / Q000503:physiopathology; D012121:Respiration, Artificial; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D014655:Vascular Resistance; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D026361:Reactive Nitrogen Species; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1