Phospholipid metabolism in alveolar macrophages of lungs. (32P)orthophosphate incorporation in pulmonary surfactant phospholipids in rat in vivo and in vitro (author's transl)

Abstract

Phospholipid Metabolism in Alveolar Macrophages of Lungs [32P]Orthophosphate Incorporation in Pulmonary Surfactant Phospholipids in Rat in vivo and in vitroPulmonary surfactant phospholipids play an important role in the surface tension activity of the lung.Incorporation of [32P]orthophosphate into rat‐lung pulmonary‐surfactant phospholipids was studied in vitro and in vivo after separation on silicic‐acid‐column chromatography and by one and two‐dimensional thin‐layer chromatography. While they represent a small part of the phospholipids of the whole lung, pulmonary‐surfactant phospholipids show a rapid turnover, particularly in vitro.After in vitro incubation, phosphatidylcholine and lysophosphatidylcholine show very important specific activities; by contrast, phosphatidylethanolamine and sphingomyelin have a very low turnover. Thus phosphatidyldimethylmethanolamine‐methylation pathway, demonstrated in the lung, is not very important.Phosphatidylglycerol is labeled more markedly in vivo than in vitro indicating, for this lipid, a possible transfer from lung tissue to pulmonary‐surfactant cells. In diphosphatidylglycerol specific activities are always very low.The incorporation of radioactive phosphate into phosphatidylinositol, more important in vitro than in vivo, is probably related to the phagocytosis activity of these cells.Our work demonstrates the existence of a phospholipid biosynthesis into pulmonary surfactant but cannot explain the metabolic relations between lung tissue and macrophagic alveolar cells investigated as a possibility in our results.