Improved quantification of lipid mediators in plasma and tissues by liquid chromatography tandem mass spectrometry demonstrates mouse strain specific differences.

A liquid chromatography tandem mass spectrometry-based method for the quantitation of 39 lipid mediators in four sample types and in two mouse strains is described. The method builds upon existing methodologies for analysis of lipid mediators by A) utilizing a bead homogenization step for tissue samples; this eliminates the need for homogenization glassware and improves homogenization consistency, B) optimizing the isolation and purification of lipid mediators with polymeric reverse phase SPE columns with lower sorbent masses; this results in lower solvent elution volumes without loss of recovery and C) utilizing an on-column enrichment method to improve analyte focusing before chromatographic separation. The method is linear from 0.25-250 pg on column for low level lipid mediators and from 5-5000 pg on column for high level lipid mediators. The addition of a methyl formate elution step to a previously published method dramatically improved precision and recovery for the cysteinyl leukotrienes. Accuracy and precision for 4 different sample types including human plasma, mouse lung, mouse spleen and mouse liver is demonstrated. Liver samples had extremely high levels of a tentatively identified bile acid which interfered with quantitation of resolvin E1, 11B-prostaglandin F2a and thromboxane A2. Results from 2 different tissue sources from untreated mice (C57BL/6 versus BALB/c) showed dramatically different concentrations of lipid mediators.