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Leukotriene E4-d5 (LTE4-d5) contains five deuterium atoms at the 19, 19', 20, 20 and 20 positions. It is intended for use as an internal standard for the quantification of LTE4 by GC- or LC-mass spectrometry. LTE4 is produced by the action of dipeptidase on LTD4, leaving only the cysteinyl group still attached to the fatty acid backbone.1 It is one of the constituents of slow-reacting substance of anaphylaxis (SRS-A).2 LTE4 is considerably less active (8 to 12-fold) than LTC4 in the biological activities characteristic of cysteinyl leukotrienes.1,3 Unlike LTC4 and LTD4, LTE4 accumulates in both plasma and urine. Therefore, urinary excretion of LTE4 is most often used as an indicator of asthma.4,5,6 In humans, basal levels of LTE4 range from 1-100 pg/mg creatinine. In asthmatic patients, urinary LTE4 levels increase to 80-1,000 pg/mg creatinine.5

1.Bernstr?m, K., and Hammarstr?m, S.Metabolism of leukotriene D by porcine kidneyJ. Biol. Chem.256(18)9579-9582(1981) 2.Samuelsson, B.Leukotrienes: Mediators of immediate hypersensitivity reactions and inflammationScience220(4597)568-575(1983) 3.Lefer, A.M.Leukotrienes as mediators of ischemia and shockBiochem. Pharmacol.35(2)123-127(1986) 4.Kumlin, M., Stensvad, F., Larsson, L., et al.Validation and application of a new simple strategy for measurements of urinary leukotriene E4 in humansClin. Exp. Allergy25(5)467-479(1995) 5.Drazen, J.M., O'Brien, J., Sparrow, D., et al.Recovery of leukotriene E4 from the urine of patients with airway obstructionAm. Rev. Respir. Dis.146(1)104-108(1992) 6.Kumlin, M., Dahlén, B., Bj?rck, T., et al.Urinary excretion of leukotriene E4 and 11-dehydro-thromboxane B2 in response to bronchial provocations with allergen, aspirin, leukotriene D4, and histamine in asthmaticsAm. Rev. Respir. Dis.146(1)96-103(1992)