Fatty acid secretion and metabolism in 'activated' rabbit alveolar macrophages.

The lipid content of bronchoalveolar lavages collected from both control rabbits and rabbits undergoing a pulmonary inflammatory response induced by intravenous injection of complete Freund's adjuvant was examined. A maximum of 4 x 10(8) alveolar macrophages could be recovered from the lavage of injected rabbits, a 10-fold greater number of cells than could be obtained from control rabbits. Increased amounts of unsaturated free fatty acids were present in the lavage lipids of injected rabbits, and no change in the amount and degree of saturation of lavaged phosphatidylcholine occurred. Alveolar macrophages recovered from injected rabbits contained 25 to 40% less lipid per cell, as measured by total fatty acid composition. Free fatty acids are released from phospholipids of adjuvant-induced alveolar macrophages incubated in vitro following lavage. Concentrations of N-formylmethionyl-phenylalanine similar to those which stimulate macrophage chemotaxis and bactericidal activity enhance this fatty acid release. Alveolar macrophages incorporate both saturated and unsaturated fatty acids with similar efficiency, primarily into phospholipids and triacylglycerols. Thus, activation of alveolar macrophages which results in a relative increase in internal phospholipase activity with concomitant large losses in cellular phospholipid results not only in liberation of chemokinetic fatty acids but also in considerable loss of membrane components.