LTD4 is one of the constituents of slow-reacting substance of anaphylaxis (SRS-A) produced by the metabolism of LTC4 by γ-glutamyl transpeptidase. LTD4-induced bronchoconstriction and enhanced vascular permeability contribute to the pathogenesis of asthma and acute hypersensitivity. LTD4 is several hundred fold more potent than LTC4 at the CysLT1 receptor, but they exhibit approximately equal affinity at the CysLT2 receptor. LTD4 methyl ester is a more lipid soluble form of LTD4. The biological activity of LTD4 methyl ester has not been reported.