A review of recent contributions on biologically active products of arachidonate conversion.

Leukotrienes (LTs) C4, D4 and E4, the recognized components of slow reacting substance of anaphylaxis (SRS-A), have previously been shown to have contractile activities for guinea pig pulmonary and ileal smooth muscles; LTB4 has been shown to possess chemotactic activity for neutrophils in vitro. Based on data obtained by the use of structural analogs of the SRS-A LTs and of LTB4, we have recently determined a number of the structural bases for the biological function of each moiety. With regard to the SRS-A leukotrienes, analogs differed from the native structures in the position of the peptide side chain and/or the hydroxyl group, the number and position of ethylenic bonds, the chirality at optically-active centers, or the structures of the four polar substituents in the C-1 to C-6 region. Analogs of LTB4, differing in the stereochemistry of their ethylenic bonds, were evaluated for chemotactic activity both in vitro, using human neutrophils, and in vivo intracutaneously in the rhesus monkey. We propose that true receptors exist on the pulmonary parenchyma of the guinea pig for the SRS-A LTs and on the primate neutrophil for LTB4. Further, LTC4, LTD4 and LTE4 have been shown to elicit a wheal and prolonged flare in human skin, whereas LTB4 evokes a time-dependent induration. The interaction of these secondary mediators may be critical to a fully developed host inflammatory response to both immunologic and non-immunologic injury.