The leukotrienes.

This paper reviews the leukotrienes, a new group of biologically active compounds in the metabolism of eicosapolyenoic acids. The leukotrienes are acyclic eicosanoids that arise through the 5-lipoxygenase pathway from eicosatrienoic, eicosatetraenoic, and eicosapentaenoic acid. Of these eicosatetraenoic acid, arachidonic acid, is the most important source of leukotrienes. Leukotriene B4 (LTB4), a dihydroxy metabolite, has been shown to exert marked chemotactic effect in many different animal species. LTB4 probably plays a role in inflammatory responses, and has been detected in several pathologic conditions. Reaction of LTA4, another lipoxygenase metabolite of arachidonic acid, with glutathione yields peptidolipid leukotrienes, LTC4, LTD4, and LTE4; these are components of slow reacting substance (SRS and SRS-A). The peptidolipid leukotrienes are potent bronchoconstrictors and enhance mucus production in the lungs. Furthermore, they constrict coronary arteries and have a negative inotropic effect. They probably play an important role in asthma and anaphylaxis. LTB4 and the peptidolipid leukotrienes may be important in several other organs, too, e.g., the skin and the eye. They may exert effects on a variety of smooth muscles and have neuronal and immunological effects.