ISOLATION AND CHARACTERIZATION OF A LUNG LIPOPROTEIN SURFACTANT

A highly surface active lipoprotein fraction was isolated in the sediment of cell-free lung wash of excised rabbit lung by a relatively simple centrifugation technique (50,000 × g, 7 C; twice for one hour, with removal of the supernatant). Based on immunology and disc electrophoresis studies we believe the lipoprotein is indigenous to lung. It consists of about 60% lipid (lecithin) and 40% protein by weight. Of the lipid, about 90% is phospholipid and 10% non-phospholipid. By gas-liquid chromatography, the total fatty acids of the lipid moiety were found to be equally distributed among saturated and unsaturated acids. In different preparations, there was a consistent mobility of bands on disc electrophoresis, and, in addition, we obtained reproducible surface pressure-area and surface potential-area curves, relating area occupied by known quantities of lipoprotein (M2/mg), spread in a 0.1% solution of amyl alcohol. The findings indicate uniformity of the lipoprotein extracted. The lipoprotein monolayers showed no hysteresis in their force-area and surface potential-area curves and remained in the liquid state. Hysteresis occurred after injection of an aliquot of a 0.9% saline minced lung extract under lipoprotein monolayers. It appears that hysteresis of films of lung extract solution is related to penetration and desorption of soluble species during expansion and compression, respectively. © 1969.