Hydrophobic lung surfactant proteins B and C remain associated with surface film during dynamic cyclic area changes

The biophysical activity of lung surfactant depends, to a large extent, on the presence of the hydrophobic surfactant proteins B (SP-B) and C (SP-C). The role of these proteins in lipid adsorption and lipid squeeze-out under dynamic conditions simulating breathing is not yet clear. Therefore, the ai m of this study was to investigate the interaction of spread hydrophobic su rfactant proteins with phospholipids in a captive-bubble surfactometer duri ng rapid cyclic area changes (6 cycles/min). We found that SP-B and SP-C fa cilitated the rapid transport of lipids into the air-water interface in a c oncentration-dependent manner (threshold concentration greater than or equa l to 0.05:0.5 mol% SP-B/SP-C). Successive rapid cyclic area changes did not affect the concentration-dependent lipid adsorption process, suggesting th at SP-B and SP-C remained associated with the surface film. (C) 1999 Elsevi er Science B.V. All rights reserved.