Chemical structure of phospholipids in the lungs and airways of sheep

Experiments on phospholipids from the alveolar lining, bronchi and trachea were conducted to support the concept that different lipid complexes are synthesized and released at different sites in the pulmonary system. Tracheal, bronchial and bronchioalveolar lavages were obtained from healthy adult Merino breed ewes following euthanasia and a structural analysis of the phospholipid fraction made by fast atom bombardment mass spectrometry. The major components in tracheal lavage were: 72% phosphatidylcholines (PC), 8% phosphatidylethanolamines (PE) and 11% phosphatidylglycerols (PG) compared to 78% PC, 13% PE and 3% PG in bronchioalveolar lavage. The fatty acid profile of tracheal lavage showed that 73% of the PG and 3% of the PC contained an arachidonic acid side chain. These species were not found in bronchioalveolar lavage. The nearly four-fold increase in PG, and the different molecular species identified in tracheal compared to bronchioalveolar lavage, suggest local synthesis and release of phospholipids by tracheal epithelial cells. The distribution of these phospholipids may have functional properties desirable for normal mucociliary function and are consistent with published measurements from cultured tracheal epithelia cells.