Morphological and lipid analysis of the alveolar lining material in dog lung.

Endobronchial saline lavage was used to obtain acellular material and cells from the dog lung. The centrifuged lavage fluid yielded a sediment consisting of an upper white layer and a lower brown layer. The white layer was strongly surface-active. It consisted of a mixture of lipids and proteins; the composition of the lipid portion was the same in three dogs. The predominant lipids were phosphatidyl choline, cholesterol, and cholesteryl esters; 75-88% of the fatty acids in each phospholipid fraction were saturated. Electron microscopy showed a strong morphological resemblance between the white layer and alveolar lining material in situ.