Analysis of platelet phospholipids by high performance liquid chromatography. II--Studies on hitherto unknown peak of phospholipid of human platelets.

With our proposed method to analyze platelet phospholipids, utilizing a normal phase high performance liquid chromatography (HPLC), it was able to quantify the amount of major platelet phospholipids (Thromb. Res. 36, 335-344, 1984). A prominent peak of unknown nature (PX) was identified close to the peak of phosphatidylcholine in the HPLC analysis of platelet phospholipids, and the attempts were made to elucidate the nature of PX. By applying several additional authentic phospholipids and those treated by acids on both the HPLC and thin layer chromatography, it was concluded that the major component of PX is 1-lyso phosphatidylethanolamine plasmalogen (PEP), artificially degraded from PEP by the acidic HPLC solvent system. No further degradation of 1-lyso PEP was observed and the absorbance of possibly co-migrated 2-lyso PE in activated platelets was negligible because it was devoid of C-2 double bonds sensitive to the absorbance used in the assay. Therefore, the relative amount of PEP may be detected based on the number of double bonds in platelet PEP. The amount of PEP thus measured was significantly decreased in thrombin-stimulated platelets, suggesting a possible participation of PEP in stimulus-linked platelet reaction.