NEUTROPHIL-DEGRANULATING ACTION OF 5,12-DIHYDROXY-6,8,10,14-EICOSATETRAENOIC ACID AND 1-O-ALKYL-2-O-ACETYL-SN-GLYCERO-3-PHOSPHOCHOLINE - COMPARISON WITH OTHER DEGRANULATING AGENTS

Abstract

5,12-Dihydroxy-6,8,10,14-eicosatetraenoic acid was prepared from rabbit neutrophils challenged with ionophore A23187 [calcimycin] plus arachidonic acid. It was purified by reverse-phase high-performance liquid chromatography with the use of a 2-step procedure that effectively resolved the lipid from closely eluting contaminants. The phospholipid 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine was prepared from beef heart plasmalogen. Both lipids stimulated human polymorphonuclear neutrophils to release granule-bound enzymes. Their respective degranulating actions took < 5 min to become maximal, were dependent upon the presence of cytochalasin B and required intact pathways of arachidonic acid metabolism, as judged by the inhibitory actions of arachidonate antimetabolites. Neither lipid required more than trace concentrations of extracellular Ca to effect optimal amounts of enzyme release. In one or more of these regards the 2 lipids differed strikingly from other neutrophil-degranulating agents such as A23187, N-formylmethionylleucyl phenylalanine and phorbol myristate acetate. The mechanism of action of the 2 lipid stimuli differ from the mechanisms of the other 3 stimuli.