Leukotriene D4 (LTD4)

Leukotriene D4 is one of the constituents of slow-reacting substance of anaphylaxis (SRS-A) produced by the metabolism of LTC₄ by gamma;-glutamyl transpeptidase. It is the first cysteinyl-leukotriene metabolite of LTC₄. Like LTC₄, LTD₄-induced bronchoconstriction and enhanced vascular permeability contribute to the pathogenesis of asthma and acute hypersensitivity. LTD₄ is equipotent to LTC₄ in its biological activities, except that LTD₄ is nearly 100-fold more effective in the contraction of peripheral airway smooth muscle. Leukotrienes are naturally produced eicosanoid lipid mediators. Leukotrienes use both autocrine signalling and paracrine signalling to regulate the body's response. Leukotrienes are produced in the body from arachidonic acid by the enzyme 5-lipoxygenase. Their production usually accompanies the production of histamine.