The molecular species composition of diacyl-, alkylacyl- and alkenylacylglycerophospholipids in rabbit alveolar macrophages. High amounts of 1-O-hexadecyl-2-arachidonyl molecular species in alkylacylglycerophosphocholine.

The relative composition of molecular species of diacyl-, alkylacyl- and alkenylacylglycerophospholipids in rabbit alveolar macrophages was determined with reverse-phase high-performance liquid chromatography (HPLC). Diacylglycerophosphocholine (GPC) (22.3% of the total glycerophospholipids), alkylacylGPC (11.3%) and alkenylacylglycerophosphoethanolamine (GPE) (15.8%) were the predominant glycerophospholipids in rabbit alveolar macrophages. DiacylGPE (6.9%), diacylGPI (5.5%) and diacylGPS (3.6%) also occurred. 1,2-Diradyl-3-acetylglycerol derived from glycerophospholipids were each resolved into 19 separate peaks with reverse-phase HPLC. By gas-liquid chromatographic quantitation of each peak, 19-29 different molecular species were identified. DiacylGPC, GPE and GPS were mainly composed of saturate, monoene and diene species, such as the 16:0-16:0, 16:0-18:1, 18:0-18:1, and 18:0-18:2 species. The predominant molecular species composing diacylGPI was the 18:0-20:4 species, which represented 40% of this glycerophospholipid. Distinct differences were found in the distributions of arachidonyl molecular species between diacyl- and ether-containing GPC and GPE. Although diacylGPC and GPE included a small amount of arachidonyl molecular species, the 16:0-20:4 species was by far the most prevalent one which composed alkylacylGPC (39% of the total) and alkenylacylGPE (49% of the total). The 16:0-20:4 species of alkylacylGPC and alkenylacylGPE together comprised 60% of the total arachidonyl molecular species of glycerophospholipids. The high amounts of the 16:0-20:4 species in alkylacylGPC may serve as a good source of both the potent platelet-activating factor and the products of arachidonic cascade in the stimulated alveolar macrophages.