leukotriene

leu·ko·tri·ene .lü-kə-'trī-.ēn n any of a group of eicosanoids that are generated in basophils, mast cells, macrophages, and human lung tissue by lipoxygenase-catalyzed oxygenation esp. of arachidonic acid and that participate in allergic responses (as bronchoconstriction in asthma) see SLOW-REACTING SUBSTANCE OF ANAPHYLAXIS

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n.

one of a class of powerful chemical agents synthesized from arachidonic acid by mast cells, basophils, macrophages, and various other tissues. Leukotrienes are involved in inflammatory reactions and the immune response: they increase the permeability of small blood vessels, cause contraction of smooth muscle, and attract neutrophils to the site of an infection.

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leu·ko·tri·ene (loo″ko-triґēn) [from leukocytes + triene indicating three double bonds] any of a group of biologically active compounds consisting of straight chain, 20-carbon carboxylic acids with one or two oxygen substituents and three or more conjugated double bonds. They are formed from arachidonic acid by the lipoxygenase pathway and function as regulators of allergic and inflammatory reactions. Leukotrienes are identified by letters A, B, C, D, and E, with subscripts indicating the number of double bonds in the molecule. Some (e.g., LTB₄) stimulate the movement of leukocytes; three others (LTC₄, LTD₄, and LTE₄) together constitute slow-reacting substance of anaphylaxis, which causes bronchial constriction and other allergic reactions.