Quantification of lysophosphatidic acids in rat brain tissue by liquid chromatography-electrospray tandem mass spectrometry.

Lysophosphatidic acid (LPA) is a lipid mediator with multiple biological functions. A highly selective and sensitive liquid chromatography-tandem mass spectrometry (LC/MS/MS) method was developed for the determination of LPAs (16:0 LPA, 18:0 LPA, 18:1 LPA, 20:4 LPA) in rat brain cryosections. After partitioning the LPAs from other lipophilic material present in the tissue with a liquid-liquid extraction, a reversed-phase column and ion pair technique was used for separating analytes with a gradient elution. An internal standard (17:0 LPA) was included in the analysis. Detection and quantification of the LPAs were carried out with a triple quadrupole mass spectrometer using negative electrospray ionization (ESI) and multiple reaction monitoring (MRM). The artificial formation of LPAs from lysophosphatidylcholines during the sample preparation procedure and instrumentation was carefully studied during the method development. The method was validated; acceptable selectivity, accuracy, precision, recovery, and stability were obtained for concentrations within the calibration curve range of 0.02-1.0muM for LPAs. The quantification limit of the assay was 54fmol injected into column for each LPAs. The method was applied to comparative studies of LPA levels in rat brain cryosections after the various chemical pre-treatments of the sections.