title: Enzymic preparation of dioxygen-18 labelled leukotriene E4 and its use in quantitative gas chromatography-mass spectrometry.
abstract: A simple and rapid method is described for the preparation of a stable isotope oxygen-18 labelled leukotriene E4 (LTE4). Oxygen-18 labelling of LTE4 methyl ester in oxygen-18 water catalysed by a pig liver esterase resulted in the incorporation of two oxygen-18 atoms in the carboxylic group of LTE4 to the extent of 89.8% ([18O2]LTE4) and one oxygen-18 atom to the extent of 9.4% ([16O18O]LTE4), with only 0.7% remaining unchanged ([16O2]LTE4). [18O2]LTE4 was found not to back-exchange following incubation in acidified urine (pH 4.0) at 4 degrees C for up to 20 h. [18O2]LTE4 was demonstrated to be a useful internal standard in a method for the quantitative determination of LTE4 in human urine involving high-performance liquid chromatography and gas chromatography with negative-ion chemical ionization tandem mass spectrometry: the concentration of LTE4 in a 24-h urine sample of a healthy subject was determined to be 68.1 pg/ml.
authors.affiliation: Department of Clinical Pharmacology, Hannover Medical School, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Tsikas
authors.forename: J
authors.initials: J
authors.lastname: Fauler
authors.forename: J C
authors.initials: JC
authors.lastname: Frölich
mesh_terms: D000818:Animals; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004950:Esterases / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D017999:Leukotriene E4; D008099:Liver / Q000201:enzymology; D013058:Mass Spectrometry; D010100:Oxygen; D010103:Oxygen Isotopes; D012016:Reference Values; D013189:SRS-A / Q000031:analogs & derivatives* / Q000378:metabolism / Q000652:urine; D013552:Swine
chemical_list: D010103:Oxygen Isotopes; D013189:SRS-A; D017999:Leukotriene E4; D004950:Esterases; D010100:Oxygen