Highly sensitive measurement of lipid molecular species from biological samples by fluorimetric detection coupled to high-performance liquid chromatography

As the molecular species composition of glycerophospholipids provides more valuable information than the corresponding fatty acid composition, we have applied a fluorimetric detection (360 and 460 nm for excitation and emission wavelengths, respectively) of anthroyl derivatives of diradylglycerol species to minor phospholipid classes and subclasses from biological samples. Diacylglycerol species were obtained by phospholipase C treatment of phosphatidylcholine subclasses and phosphatidic acid extracted from rat thymocytes. Subpicomole measurements of molecular species from the minor subclass alkenylacylglycerophosphocholine could be achieved (e.g. 0.4 pmol of the 18:1/20:5 species). Such a sensitivity allowed study of the molecular species composition of another minor phospholipid, phosphatidic acid, and to evaluation of its alteration in mitogen-stimulated thymocytes as compared to unstimulated ones. Finally, we report that such a measurement is also applicable to other minor bioactive lipids with a hydroxyl group available, namely hydroxyeicosatetraenoates (HETEs), with a similar gain of sensitivity over conventional UV detection. Overall, these measurements, especially those of phospholipid molecular species, are sensitive, reliable and meaningful for precursor–product relationship between phospholipids.