Platelet serotonin content and transpulmonary platelet serotonin gradient in patients with pulmonary hypertension.
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.
Ulrich
Silvia
S
Department of Medicine and Pulmonology, Clinic and Policlinic of Internal Medicine, University Hospital of Zurich, Zurich, Switzerland. silvia.ulrich@usz.ch
Huber
Lars C
LC
Fischler
Manuel
M
Treder
Ursula
U
Maggiorini
Marco
M
Eberli
Franz Robert
FR
Speich
Rudolf
R
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*
D012701:Serotonin