title: Pleural transport physiology: insights from biological marker measurements in transudates.
abstract: OBJECTIVE
  The aim of this study was to evaluate the physicochemical properties of the pleural mesothelial barrier and of the biological markers that facilitate or eliminate the passage of molecules through the pleura.
  
  
  METHODS
  Pleural fluid samples from sixty-five patients with heart failure were analyzed. The biological markers studied were lactate dehydrogenase (LDH), adenosine deaminase (ADA), interleukin-6 (IL-6), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), carcinoembryonic antigen (CEA), copper/zinc superoxide dismutase (CuZnSOD), matrix metalloproteinase-2 (MMP-2), -3 (MMP-3), -7(MMP-7), -8 (MMP-8) and -9 (MMP-9). Based on the pleural fluid/serum ratio, these molecules were divided into three groups: a) the LDH-like group with a pleural fluid/serum ratio between 0,4 and 0,8 (LDH, CEA, CuZnSOD, ADA, CRP, MMP-8), b) molecules with a pleural fluid/serum ratio less than 0,4 (MMP-7 and MMP-9) and c) molecules with a pleural fluid/serum ratio equal or above 1 (TNF-α, IL-6, MMP-2 and MMP-3).
  
  
  RESULTS
  No correlation between the molecular radius and the pleural fluid to serum ratio of the above biological markers was found.
  
  
  CONCLUSIONS
  The molecular size is not a major determinant for the passage of molecules through the mesothelial barrier. Several other factors may influence the transport of the above molecules to pleural cavity, such as their charge and shape.
authors: Department of Physiology, University of Thessaly Medical School, Larissa, Biopolis, 41110, Greece.
authors: Eleni
authors: E
authors: Apostolidou
authors: Irini
authors: I
authors: Tsilioni
authors: Chrissi
authors: C
authors: Hatzoglou
authors: Paschalis-Adam
authors: PA
authors: Molyvdas
authors: Konstantinos I
authors: KI
authors: Gourgoulianis