Arachidonic acid metabolism in polymorphonuclear leukocytes

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Abstract
Addition of arachidonic acid and the divalent cation inophore A23187 to a suspension of human peripheral blood polymorphonuclear leukocytes led to the formation of (5S)-hydroxy-6,8,11,14-icosatetraenoic acid, (15S)-hydroxy-5,8,11,13-icosatetraenoic acid and (5S,12R)-dihydroxy-6,8,10,14-icosatetraenoic acid. A method based on high-pressure liquid chromatography was developed for assay of these metabolites. The addition of arachidonic acid to human polymorphonuclear leukocytes always resulted in formation of the isomeric monohydroxy acids. Cells prepared from blood of different subjects varied with respect to formation of the 5,12-dihydroxy acid. Addition of the ionophore alone strongly stimulated the formation of the 5-monohydroxy acid and more specifically the 5,12-dihydroxy acid from endogenous arachidonic acid. In all experiments performed the formation of the 5-hydroxy acid and the 5,12-dihydroxy acid was maximally stimulated when arachidonic acid and the ionophore were added to the incubation mixture. Under these conditions, stimulation of 40-fold or more of the formation of both compounds was observed. In addition to causing release of endogenous substrate, the ionophore also activated the enzymatic system involved in the further transformation of arachidonic acid. This pathway of arachidonic acid metabolism may be involved in the biological response (e.g., release of lysosomal enzymes, the slow reacting substance of anaphylaxis and chemotactic factors) of leukocytes to A23187 and other stimuli.