Role of lipid ordered/disordered phase coexistence in pulmonary surfactant function.
The respiratory epithelium has evolved to produce a complicated network of extracellular membranes that are essential for breathing and, ultimately, survival. Surfactant membranes form a stable monolayer at the air-liquid interface with bilayer structures attached to it. By reducing the surface tension at the air-liquid interface, surfactant stabilizes the lung against collapse and facilitates inflation. The special composition of surfactant membranes results in the coexistence of two distinct micrometer-sized ordered/disordered phases maintained up to physiological temperatures. Phase coexistence might facilitate monolayer folding to form three-dimensional structures during exhalation and hence allow the film to attain minimal surface tension. These folded structures may act as a membrane reserve and attenuate the increase in membrane tension during inspiration. The present review summarizes what is known of ordered/disordered lipid phase coexistence in lung surfactant, paying attention to the possible role played by domain boundaries in the monolayer-to-multilayer transition, and the correlations of biophysical inactivation of pulmonary surfactant with alterations in phase coexistence.
Departamento de Bioquimica y Biologia Molecular, Universidad Complutense de Madrid, Madrid, Spain. ccasalscc@bio.ucm.es
Cristina
C
Casals
Olga
O
Cañadas
D008055:Lipids / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry; D011650:Pulmonary Alveoli / Q000502:physiology; D011663:Pulmonary Surfactants / Q000378:metabolism*; D013500:Surface Tension
D008055:Lipids; D011506:Proteins; D011663:Pulmonary Surfactants