“Alveolar” and Whole Lung Phospholipids of Newborn Lambs ∗

Summary

Fifteen newborn lambs ranging in age from 10 min to 192 hours were studied. The qualitative and quantitative nature of “alveolar” phospholipids and whole lung tissue phospholipids were determined and compared with data previously obtained on term fetuses. Sequential lung washings removed practically all of the surface-active material from the internal surface of the lung. The “alveolar” phospholipids increased twofold in 10 min after the onset of respiration, fourfold in the first 24 hours and eightfold in the second day of life. The “alveolar” phospholipid composition of the newborn is similar to the term fetus, but differs from whole lung tissue phospholipids. The percentage minimal disaturates of the phosphatidylcholine of the newborn is slightly higher than that of the term fetus. “Alveolar” disaturated phosphatidylcholine represents the major portion of dipalmitoyl phosphatidylcholine. Phosphatidyldimethylethanolamine was isolated from “alveolar” phospholipids. This phospholipid contains a higher concentration of disaturated phosphatidyldimethylethanolamine in the newborn than in the fetus. It is concluded that respiration of the newborn has a profound effect both mechanically and metabolically upon the liberation and elaboration of surface-active material.