Leukotriene A4-d5 methyl ester

Leukotriene A4-d5 (LTA4-d5) methyl ester contains four deuterium atoms at the 19, 19', 20, 20, and 20 positions. It is intended for use as an internal standard for the quantification of LTA4 methyl ester by GC- or LC-mass spectrometry. LTA4 is synthesized in mast cells, eosinophils, and neutrophils from arachidonic acid by 5-lipoxygenase (5-LO), which exhibits both lipoxygenase and LTA4 synthase activities.{595,482} LTA4 is rapidly metabolized by LTA4 hydrolase or LTC4 synthase to LTB4 or LTC4, respectively.{482} LTA4, from leukocytes, is known to undergo transcellular metabolism in platelets, erythrocytes, and endothelial cells.{781} Further metabolism of LTA4 by 15-LO leads to lipoxin biosynthesis.{482} LTA4 as a free acid is highly unstable. The methyl ester is stable and can be readily hydrolyzed to the free acid as needed.