Lipids in airway secretions.

Lipids form a significant portion of airway mucus yet they have not received the same attention that epithelial glycoproteins have. We have analyzed, by thin layer chromatography, lipids present in airway mucus under "normal" and hypersecretory (pathological) conditions. The 'normals' included (1) bronchial lavage obtained from healthy human volunteers and from dogs and (2) secretions produced "in vitro" by human (bronchial) and canine (tracheal) explants. Hypersecretory mucus samples included (1) lavage from dogs made bronchitic by exposure to SO2, (2) bronchial aspirates from acute and chronic tracheostomy patients, (3) sputum from patients with cystic fibrosis and chronic bronchitis and (4) postmortem secretions from patients who died from sudden infant death syndrome (SIDS) or from status asthmaticus. Cholesterol was found to be the predominant lipid in 'normal' mucus with lesser amounts of phospholipids. No glycolipids were detected. In the hypersecretory mucus, in addition to neutral and phospholipids, glycolipids were present in appreciable amounts, often the predominant species, suggesting that these may be useful as markers of disease. Radioactive precursors 14C acetate and 14C palmitate were incorporated into lipids secreted "in vitro" by canine tracheal explants indicating that they are synthesised by the airway.