title: Leukotriene E4 elimination and metabolism in normal human subjects.
abstract: Radiolabeled leukotriene (LT) E4 was infused into three healthy subjects in order to assess the production and elimination of sulfidopeptide leukotriene metabolites in urine. Three different radiolabeled tracers were employed, [14,15-3H]LTE4, [35S]LTE4, and [14C] LTE4 in five separate infusion studies. There was a rapid disappearance of radioactivity from the vascular compartment in an apparent two-phase process. The first elimination phase had an apparent half-life of approximately 7 min. Radioactivity quickly appeared in the urine with 10-16% eliminated during the first 2 h following intravenous infusion; 7%, 2-5 h; 4%, 5-8 h; 4%, 8-15 h; and 1.5%, 15-24 h from the [14C] LTE4 experiments. Unmetabolized LTE4 was the major radioactive component in the first urine collection, but at later times two more polar compounds predominated. After extensive purification by normal phase-solid phase extraction and reverse-phase high performance liquid chromatography, these compounds were characterized by UV spectroscopy, co-elution with synthetic standards, negative ion electron capture gas chromatography/mass spectrometry, and tandem mass spectrometry. The two major urinary metabolites were structurally determined to be 14-carboxy-hexanor-LTE3 and the conjugated tetraene, 16-carboxy-delta 13-tetranor-LTE4. Three other minor metabolites were detectable in the first urine collection only and were characterized by co-elution with synthetic standards as 16-carboxy-tetranor-LTE3, 18-carboxy-dinor-LTE4, and 20-carboxy-LTE4. omega-Oxidation and subsequent beta-oxidation from the methyl terminus appeared to be the major metabolic fate for sulfidopeptide leukotrienes in man. The accumulation of the 14-COOH-LTE3 and 16-COOH-delta 13-LTE4 may reflect a rate-limiting step in further oxidation of these compounds which places a conjugated triene or conjugated tetraene, respectively, two carbons removed from the CoA ester moiety. Also in the first urine collection there was another minor metabolite identified as N-acetyl-LTE4, however, no subsequent beta-oxidation of this metabolite was observed. The major metabolites of LTE4 might be useful in assessing in vivo production of sulfidopeptide leukotrienes in humans.
authors.affiliation: Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver 80206.
authors.forename: A
authors.initials: A
authors.lastname: Sala
authors.forename: N
authors.initials: N
authors.lastname: Voelkel
authors.forename: J
authors.initials: J
authors.lastname: Maclouf
authors.forename: R C
authors.initials: RC
authors.lastname: Murphy
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D017999:Leukotriene E4; D008297:Male; D013058:Mass Spectrometry; D008657:Metabolic Clearance Rate; D013189:SRS-A / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics; D013056:Spectrophotometry, Ultraviolet
chemical_list: D013189:SRS-A; D017999:Leukotriene E4