Normal surface properties of phosphatidylglycerol-deficient surfactant from dog after acute lung injury

Lung surfactant was isolated from bronchoalveolar lavage of dogs during the late phase of recovery (15 days) from acute alveolar injury induced by subcutaneous injection of N-nitroso-N-methylurethane. This surfactant was compared with surfactant from control dogs in terms of in vitro surface properties, phospholipid composition and protein content, and those of its subfractions. Phospholipid composition and protein content were similar in the two groups, except that phosphatidylglycerol (PG) was markedly reduced and phosphatidylinositol (PI) was increased in the experimental group. In both, isopycnic densities of their subfractions in continuous sucrose density gradient were identical. The time course of surfactant adsorption was similar in both groups. Minimum surface tension (gamma min) was 4.1 +/- 1.5 dynes/cm in the experimental dogs and 3.8 +/- 1.3 dynes/cm in the controls. Surface compressibility (SC), stability index (SI), and dynamic respreadability (DR) of the surfactants from the two groups were nearly identical. When compared to an artificial surfactant composed of dipalmitoyl phosphatidylcholine (DPPC) and PG in 9:1 molar ratio a mixture of DPPC-PI 9:1 prepared identically showed similar gamma min, SC, SI, and DR, and a much higher surface adsorption rate. These results suggest that PG is not essential for normal in vitro surfactant function and that its role may be assumed by PI.