THE ROLE OF LIPIDS IN PULMONARY SURFACTANT

Pulmonary surfactant is composed of approx. 90% lipids and 10% protein . This review article focusses on the lipid components of surfactant. The first sections will describe the lipid composition of mammalian su rfactant and the techniques that have been utilized to study the invol vement of these lipids in reducing the surface tension at an air-liqui d interface, the main function of pulmonary surfactant. Subsequently, the roles of specific lipids in surfactant will be discussed. For the two main surfactant phospholipids, phosphatidylcholine and phosphatidy lglycerol, specific contributions to the overall surface tension reduc ing properties of surfactant have been indicated. In contrast, the rol e of the minor phospholipid components and the neutral lipid fraction of surfactant is less clear and requires further study. Recent technic al advances, such as fluorescent microscopic techniques, hold great po tential for expanding our knowledge of how surfactant lipids, includin g some of the minor components, function. Interesting information rega rding surfactant lipids has also been obtained in studies evaluating t he surfactant system in non-mammalian species. In certain non-mammalia n species (and at least one marsupial), surfactant lipid composition, most notably disaturated phosphatidylcholine and cholesterol, changes drastically under different conditions such as an alteration in body t emperature. The impact of these changes on surfactant function provide insight into the function of these lipids, not only in non-mammalian lungs but also in the surfactant from mammalian species. (C) 1998 Else vier Science B.V. All rights reserved.