title: Platelet serotonin content and transpulmonary platelet serotonin gradient in patients with pulmonary hypertension.
abstract: BACKGROUND
  The serotonin system has repeatedly been associated with the pathogenesis of pulmonary hypertension (PH).
  
  
  OBJECTIVE
  To comparatively analyze plasmatic and intrathrombocytic serotonin levels in arterial and mixed venous blood of patients with PH and unaffected controls to elucidate pulmonary serotonin metabolisms.
  
  
  METHODS
  Catheters were placed in the radial and pulmonary artery in patients with PH (n = 13) for diagnosis and in age-matched controls (n = 6) undergoing percutaneous closure of the patent foramen ovale. Arterial and mixed venous blood samples were immediately centrifuged to obtain plasma and platelets and thereafter frozen at -20°C. After careful thawing, plasmatic and platelet serotonin levels were determined by ELISA.
  
  
  RESULTS
  PH was classified as arterial in 4 and chronic thromboembolic in 9 patients with a mean pulmonary artery pressure of 37 (interquartile range: 32-43) mm Hg. Platelet serotonin content was significantly lower in the PH patients than in the controls. The mean transpulmonary gradient (arterial-mixed venous) was negative in the PH group and positive in the controls. An inverse correlation was found between the arterial blood platelet serotonin content and pulmonary hemodynamics. Plasmatic serotonin levels did not differ between the PH and control groups.
  
  
  CONCLUSIONS
  The lower platelet serotonin concentration in PH patients compared with unaffected controls is an unprecedented finding. The negative transpulmonary platelet serotonin gradient and the strong negative correlation of arterial blood platelet serotonin with pulmonary hemodynamics might indicate increased serotonin uptake in the lungs of PH patients.
authors.affiliation: Department of Medicine and Pulmonology, Clinic and Policlinic of Internal Medicine, University Hospital of Zurich, Zurich, Switzerland. silvia.ulrich@usz.ch
authors.forename: Silvia
authors.initials: S
authors.lastname: Ulrich
authors.forename: Lars C
authors.initials: LC
authors.lastname: Huber
authors.forename: Manuel
authors.initials: M
authors.lastname: Fischler
authors.forename: Ursula
authors.initials: U
authors.lastname: Treder
authors.forename: Marco
authors.initials: M
authors.lastname: Maggiorini
authors.forename: Franz Robert
authors.initials: FR
authors.lastname: Eberli
authors.forename: Rudolf
authors.initials: R
authors.lastname: Speich
mesh_terms: D000368:Aged; D001792:Blood Platelets / Q000378:metabolism*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000097:blood*; D008168:Lung / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012701:Serotonin / Q000097:blood*
chemical_list: D012701:Serotonin