(loo‵kō-trī'ēn )

Any of a group of arachidonic acid metabolites that functions as a chemical mediator of allergic reactions and inflammation. Leukotrienes C₄, D₄, and E₄ are derived from the precursor molecule leukotriene A₄. The subscripted number specifies the number of double bonds in the molecule. All are synthesized by cells in response to inflammation or tissue injury. Leukotrienes have been implicated in the development of the inflammatory responses in asthma, psoriasis, rheumatoid arthritis, and inflammatory bowel disease. They are powerful bronchoconstrictors and vasodilators and mediate the adverse vascular and bronchial effects of systemic anaphylaxis.