Monomolecular surface film and tubular myelin figures of the pulmonary surfactant in hamster lung.

Perfusion fixation via pulmonary trunk was applied to the alveolar lining layer in situ at different lung volumes using a fixative containing tannic acid-ferrocyanide osmium. The monomolecular surface film and hypophasic tubular myelin figures were enhanced. In the range of transpulmonary pressure (1-10 cmH2O), the surface film appeared in the form of a single, electron-dense leaflet, 2.7 +/- 0.6 nm (M +/- SD) in thickness while trilaminar membrane structure was retained in all parts of the tubular myelin figures of the hypophase. The surface film was attached underneath at right angles with trilaminar membranes which formed the outermost parts of the tubular myelin. Such structural continuity was taken to support a view that the phospholipid unit membrane of the tubular myelin figure would be transformed at the hydrophobic phase into a pair of monomolecular leaflets, eventually forming the surface film.