A comparison of the surfactant associated lipids derived from reptilian and mammalian lungs.

The lungs of the central netted dragon Ctenophorus nuchalis are bag-like, with most of the gas exchange region located in the anterior third. Although the faveoli are much larger than the mammalian alveoli, the lizard at 37 degrees C has approximately 70 times more surfactant phospholipid per unit area of respiratory surface than does a similar sized mammal. However, when expressed as per wet lung weight, lizards and rats possessed similar amounts of phospholipids. Dipalmitoylphosphatidylcholine was the principal phospholipid in both species. However, major differences existed in the phospholipid, neutral lipid and fatty acid profiles. Whereas the lizard contained neither phosphatidylglycerol nor phosphatidylethanolamine it had more cholesterol, esterified cholesterol, acylglycerides and unsaturated fatty acids. Although the ratio of saturated:unsaturated fatty acids was similar in rats and lizards, palmitic acid predominated in the former. The composition of lizard surfactant suggests that it would adsorb rapidly at reduced body temperature.