The Hydrophobic Surfactant Proteins Destabilize Pulmonary Surfactant Monolayers

• DOI: 10.1096/fasebj.22.1_supplement.931.2
• Publication Date: 2021-06-21T23:01:41Z
• Authors: Stephen B. Hall; Florence Lhert; Wenfei Yan; Samares C. Biswas
• Keywords: 0301 basic medicine; 03 medical and health sciences

To determine if the hydrophobic surfactant proteins affect the stability of pulmonary surfactant monolayers at an air/water interface, we compared the kinetics of collapse for the complete set of lipids in calf surfactant with and without the proteins. Monomolecular films spread at the surface of captive bubbles were compressed at 37°C to surface pressures (π) above 46 mN/m, at which collapsed first occurred. The rate of area‐compression required to maintain constant π determined the rate of collapse. For films with and without the proteins, higher π initially produced faster collapse, but the rates then reached a maximum and decreased to minimal values. The maximum rate for the lipids with the proteins was almost twice the value for the lipids alone. Because small changes in π produced large shifts in the rate close to the fastest collapse, compressions at constant rates also established the threshold speed required to achieve high π as an indirect measure of the fastest collapse. Both samples produced a sharply defined threshold that occurred at slightly faster compression with the proteins present, supporting the direct measurements that the proteins produce a faster maximum rate of collapse. At 47–53 mN/m, the hydrophobic surfactant proteins destabilize the compressed monolayers, and tend to limit access to the higher π at which the lipid films become metastable.