Dipalmitoyl lecithin and lung surfactant adsorption at an air-liquid interface by respirable particles

The effects of kaolin and flyash on synthetic dipalmitoyl lecithin and lung surfactant from the lavage of excised rat lungs were studied using a Wilhelmy-type surface balance. After control studies with dipalmitoyl lecithin and rat lung surfactant, particles were sprinkled onto the surface at minimum surface area and the surface tensions vs surface areas were recorded. The results showed increased minimum surface tensions and decreased hysteresis areas when the particles were added. More particles were required to change the hysteresis area of lung surfactant than were required for synthetic dipalmitoyl lecithin. The effects of changes in surface areas of alumina and zinc oxide particles on dipalmitoyl lecithin were also studied. The amount of particles required to reduce surface tension-surface area hysteresis increased as the particles' surface area per gram decreased. This study indicates that respirable dusts may adsorb dipalmitoyl lecithin or lung surfactant in vivo and, therefore, may prevent surface tension from reaching the low values generally thought to occur in vivo.