Mass spectrometric quantification of cysteine-containing leukotrienes in rat bile using13C-labeled internal standards

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Abstract
Leukotriene C4 and N‐acetyl leukotriene E4 were determined in rat bile using a procedure based on high‐performance liquid chromatographic fractionation, hydrogenation to 5‐hydroxyeicosanoic acid, and gas chomatographic/mass spectrometric selected ion monitoring analysis of the pentafluorobenzyl ester, trimethylsilyl ether derivatives. 13C4‐Labeled analogs of the leukotrienes were synthesized and used as internal standards. The concentrations of both leukotrienes in rat bile were markedly elevated after administration of endotoxin to anesthetized animals; N‐acetyl leukotriene E4 was the more abundant product. The presence of leukotriene C4 in rat bile after endotoxin challenge was confirmed by fast atom bombardment/tandem mass spectrometry with precursor ion scanning. Quantitative determination of leukotriene C4 using the tandem mass spectrometric procedure was consistent wth the gas chromatographic/mass spectrometric data but the latter procedure gave a substantially lower detection limit.