Oxygen transport through lung surfactant and the surfactant specific proteins

At the very beginning of its migration pathway to any tissue, oxygen has to cross the lung surfactant surface layer (LSSL) and the underlying aqueous hypophase. The influence of human broncho-alveolar lavage and its lipid and specific protein components on oxygen transport were studied in vitro using sensitive electrochemical techniques. LSSL adsorbing from BAL at the dropping mercury electrode/saline interface shifted the peak potentials of oxygen reduction Ep towards more negative values. The magnitude of delta Ep was dependent on the quality of BAL. The kinetics of the oxygen transport were evaluated by measuring changes in the intensities of the reduction current. Storage of oxygen in BAL was several times higher than in saline and indicated the presence of one or more binding sites or promoters for oxygen among BAL components. The surfactant specific protein was found to be one of the binding sites (or promoters) for the oxygen. Since electron microscopic immuno-gold labelling demonstrated the presence of this protein in the LSSL, and electrochemically it proved to transport lipids from the surface layer to the subphase, it was suggested that Sp-A plays the role of an oxygen carrier.