Experimental Pneumonitis : Changes in the Phospholipid Metabolism of the Lung of Guinea Pigs and Rats

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Changes of the metabolism of lung phospholipids and alveolar wash lipids were studied in guinea pigs and rats with experimental pneumonitis produced by the injection of complete Freund's adjuvant. The amount of total lipid obtained by lung lavage decreased significantly in contrast to a marked increase in the content of total protein in treated animals. Among the lipids in the pulmonary washings, only phospholipids were strikingly reduced, and free fatty acids were increased some what. However, the composition of phospholipids was not affected by the treatment. The in vitro incorporation of 1-¹⁴C-acetate into the total lipid and phospholipids in the lung with pneumonitis was slightly lower compared to controls, but the difference was not significant. The in vitro 1-¹⁴C-palmitic acid incorporation into phospholipids of the lesioned lung, was also similar to that in controls. Thus, phospholipid biosynthesis in the lung was not affected by pneumonitis. On the other hand, the in vitro activity of total phospholipase in rat lung with experimental pneumonitis was enhanced significantly. These results suggest that phospholipase activity is increased in the diseased lung and this may participate in the process of the inflammatory reaction. The possible role of activated macrophages in the inflammatory response of the lung is discussed.