A second pathway of leukotriene biosynthesis in porcine leukocytes.

Abstract

Incubation of suspensions containing polymorphonuclear and eosinophilic leukocytes with arachidonic acid led to the formation of 2 pairs of diastereomeric 8,(15S)-dihydroxy-5,9,11,13-eicosatetraenoic acids and 2 erythro-14,15-dihydroxy-5,8,10,12-eicosatetraenoic acids. The structures were elucidated by UV spectroscopy and gas chromatography-mass spectrometric analysis of several derivatives of each compound, catalytic hydrogenation, oxidative ozonolysis with steric analysis of alcohols and comparison to reference compounds prepared by chemical synthesis. Experiments with 18O2 and H218O indicated that in all 6 compounds the hydroxyl group at C-15 was derived from molecular oxygen. Two of the diastereomeric 8,15-dihydroxy acids incorporated H219O at C-8, while the other two, 8,15-dihydroxy products (also diastereomers) and the 14,15-dihydroxy compounds (geometric isomers) incorporated 18O2 at C-8 and C-14, respectively, in addition to C-15. Two of the 8,15-dihydroxy acids are formed by reaction of H2O with an unstable allylic epoxide intermediate, (14S. 15S)-oxido-5,8,10,12-eicosatetraenoic acid; the two 14,15-dihydroxy acids are proposed to be formed by reaction of activated molecular oxygen with the same epoxide, which in turn originates via 15S oxygenation of arachidonic acid.