title: Sildenafil inhibits hypoxia-induced pulmonary hypertension.
abstract: BACKGROUND
  This study investigated the effect of the phosphodiesterase 5 inhibitor sildenafil on the pulmonary vascular response to hypoxia in humans and mice.
  
  
  RESULTS
  In a randomized, double-blind study, sildenafil 100 mg or placebo was given orally to 10 healthy volunteers 1 hour before breathing 11% O(2) for 30 minutes. Pulmonary artery pressure (PAP) was measured with an indwelling right heart catheter. The acute 56% increase in mean PAP produced by hypoxia during placebo treatment (mean PAP [mean+/-SD mm Hg]: normoxia 16.0+/-2.1 versus hypoxia 25.0+/-4.8) was almost abolished by sildenafil (normoxia 16.0+/-2.1 versus hypoxia 18.0+/-3.6), with no significant effect on systemic blood pressure. In the isolated perfused lung of wild-type and endothelial nitric oxide synthase (eNOS)-deficient mice, sildenafil markedly blunted acute hypoxic pulmonary vasoconstriction. Wild-type mice dosed orally with the drug (25 mg. kg(-1). d(-1)) throughout 3 weeks of exposure to hypoxia (10% O(2)) exhibited a significant reduction in right ventricular systolic pressure (placebo versus sildenafil: 43.3+/-9.9 versus 29.9+/-9.7 mm Hg, P<0.05) coupled with a small reduction in right ventricular hypertrophy and inhibition of pulmonary vascular remodeling. In eNOS mutant mice, sildenafil attenuated the increase in right ventricular systolic pressure but without a significant effect on right ventricular hypertrophy or vascular remodeling.
  
  
  CONCLUSIONS
  Sildenafil attenuates hypoxia-induced pulmonary hypertension in humans and mice and offers a novel approach to the treatment of this condition. The eNOS-NO-cGMP pathway contributes to the response to sildenafil, but other biochemical sources of cGMP also play a role. Sildenafil has beneficial pulmonary hemodynamic effects even when eNOS activity is impaired.
authors.affiliation: Section on Clinical Pharmacology, Imperial College School of Medicine, Hammersmith Hospital, London, UK.
authors.forename: L
authors.initials: L
authors.lastname: Zhao
authors.forename: N A
authors.initials: NA
authors.lastname: Mason
authors.forename: N W
authors.initials: NW
authors.lastname: Morrell
authors.forename: B
authors.initials: B
authors.lastname: Kojonazarov
authors.forename: A
authors.initials: A
authors.lastname: Sadykov
authors.forename: A
authors.initials: A
authors.lastname: Maripov
authors.forename: M M
authors.initials: MM
authors.lastname: Mirrakhimov
authors.forename: A
authors.initials: A
authors.lastname: Aldashev
authors.forename: M R
authors.initials: MR
authors.lastname: Wilkins
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D004311:Double-Blind Method; D005838:Genotype; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006801:Humans; D006976:Hypertension, Pulmonary / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D006984:Hypertrophy; D000860:Hypoxia / Q000150:complications*; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010726:Phosphodiesterase Inhibitors / Q000627:therapeutic use*; D010879:Piperazines / Q000627:therapeutic use*; D011651:Pulmonary Artery / Q000187:drug effects / Q000503:physiopathology; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones; D016278:Ventricular Function, Right / Q000187:drug effects
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D006152:Cyclic GMP