title: The noradrenaline plasma concentration and its gradient across the lung.
abstract: BACKGROUND
  We investigated the lung contribution to circulating noradrenaline (NA) homeostasis. Evaluation of the transpulmonary NA gradient, related to the NA amount entering the lungs, is potentially important, mainly regarding clinical conditions, such as congestive heart failure (CHF), that are associated with excessive circulating NA.
  
  
  METHODS
  15 moderate (group 1) and 15 severe (group 2) CHF patients, and 10 normal individuals had determination of NA transpulmonary gradient in the baseline and during rise (exercise, in normals and group 1) or fall (withdrawal from plasma by ultrafiltration, in group 2) of plasma NA.
  
  
  RESULTS
  NA gradient (pg mL(-1)) at rest was 30 +/- 3 in normals, 21 +/- 6 in group 1 and 5 +/- 8 in group 2. Increase of NA concentration in the mixed venous blood with exercise was paralleled by depression of the transpulmonary gradient. Pulmonary arteriovenous difference disappeared when NA entering the lungs averaged 1300 pg mL(-1). In group 2, ultrafiltration lowered NA in the mixed venous blood from 1225 +/- 213 to 718 +/- 182, which caused transpulmonary gradient to increase from 5 +/- 8 to 22 +/- 9.
  
  
  CONCLUSIONS
  Transpulmonary gradient of NA diminishes when NA entering the lungs increases, and 1300 pg mL(-1) in the pulmonary artery is, both in patients and normal subjects, the level at which gradient disappears; which likely reflects cessation of NA uptake or achievement of a balance between lung uptake and production. This may have physiological and pathological implications.
authors.affiliation: Istituto di Cardiologia dell'Università degli Studi, Centro di Studio per le Ricerche Cardiovascolari del Consiglio Nazionale delle Ricerche, Centro Cardiologico, I.R.C.C.S., Milan, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Marenzi
authors.forename: P
authors.initials: P
authors.lastname: Agostoni
authors.forename: M
authors.initials: M
authors.lastname: Guazzi
authors.forename: G
authors.initials: G
authors.lastname: Lauri
authors.forename: E
authors.initials: E
authors.lastname: Assanelli
authors.forename: M D
authors.initials: MD
authors.lastname: Guazzi
mesh_terms: D000368:Aged; D015444:Exercise; D005260:Female; D006333:Heart Failure / Q000378:metabolism; D006439:Hemodynamics; D006440:Hemofiltration; D006706:Homeostasis; D006801:Humans; D008168:Lung / Q000098:blood supply / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood* / Q000378:metabolism; D011651:Pulmonary Artery / Q000378:metabolism; D012044:Regression Analysis
chemical_list: D009638:Norepinephrine