LTD4 is one of the constituents of slow-reacting substance of anaphylaxis (SRS-A) produced by the metabolism of LTC4 by γ-glutamyl transpeptidase.{541,589} LTD4-induced bronchoconstriction and enhanced vascular permeability contribute to the pathogenesis of asthma and acute hypersensitivity.{4157,482} LTD4 is several hundred fold more potent than LTC4 at the CysLT1 receptor, but they exhibit approximately equal affinity at the CysLT2 receptor.{7174,8519} LTD4 methyl ester is a more lipid soluble form of LTD4. The biological activity of LTD4 methyl ester has not been reported.