Arachidonic acid metabolism in polymorphonuclear leukocytes: unstable intermediate in formation of dihydroxy acids.

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Abstract
An unstable intermediate was detected in the transformation of arachidonic acid into 5,6-dihydroxyicosatetraenoic acids (2 isomers) and 5,12-dihydroxyicosatetraenoic acids (3 isomers) in rabbit peritoneal (glycogen-induced) polymorphonuclear leukocytes. Addition of 10 vol of methanol, ehtanol or ehtylene glycol to short-term incubations (30-45 s) led to formation of the corresponding 12-O-alkyl derivatives of the 5,12-dihydroxy acids. The time for 50% disappearance of the intermediate (37.degree. C), as measured by formation of 5-hydroxy-12-O-methylicosatraenoic acids (2 isomers) upon trapping with methanol, was about 1 min in live cell preparations (pH 7.4) and about 4 min in water/acetone (1:1), pH 7.4. At pH 6.0 or below, hydrolysis of the intermediate was too rapid to be measured by the method employed. Data supporting enzymatic and nonenzymatic hydrolysis of the intermediate into dihydroxy acids were presented. Incubation of the cells with arachidonic acid under an atmosphere of 18O2 led to incorporation of 18O into the 5,6-dihydroxy acids and 5,12-dihydroxy acids only at C-5. The 5-hydroxyicosatetraenoic acid was also labeled at C-5. Considering chemical reactivity of the intermediate and structures of the deriviatives obtained, the intermediate may be 5(6)-oxido-7,9,11,14-icosatetraenoic acid.