The relationship of fatty acid composition and surface activity of lung extracts.

Male weanling rats were fed fat-free diets supplemented with 4% (w/w) safflower oil (control) or 4% tripalmitin (essential fatty acid (EFA) deficient) for 14 weeks. Whereas the amount of lecithin in lung lavage material remained unchanged, lung lavage lecithin from EFA-deficient rats contained significantly less palmitic acid (61.4 +/- 2.0% vs. 77.4 +/- 5.8%, P less than 0.01) than that from controls. Surface tension vs. area hysteresis loops were obtained for total lipid extracts (TLE) of lung lavage fluid, intra- and extra-cellular lipoprotein fractions (IBI and IBE) and lipid extracts of those lipoprotein fractions (LBI and LBE). A significant increase in minimal surface tension (gammamin) was found for all samples obtained from EFA-deficient rats as compared to controls. Refeeding of diets containing safflower oil for 7-14 days reversed these changes. Air pressure-volume curves on degassed, excised lungs indicated that greater pressure is required to maintain a given lung volume in EFA-deficient rats. These results support the hypothesis that the fatty acid composition of pulmonary surfactant lecithins is a major determinant of the surface activity of lung extracts.