Incubation of an isoenzyme of phospholipase A2 (PLA2, isolated from snake venom) with porcine leukocytes resulted in the formation of several trihydroxytetraene- containing compounds which were derived from endogenous sources of arachidonic acid. The formation of these endogenous compounds was dose-dependent with an EC50 of approximately 1.25 x 10(-8) M. At this concentration of the isoenzyme and time (10 min) of explosure the cells remained viable as determined by the exclusion of trypan blue. The trihydroxytetraene compounds were purified by RP-HPLC and their identities were analyzed by U.V. spectrometry, GC/MS and by comparison with synthetic materials. The biologically derived compounds proved to be lipoxin B4 (5S, 14R, 15S-trihydroxy-6,10,12-trans-8-cis-eicosatetraenoic acid) and its two structural isomers (8-trans-LXB4 and 14S-8-trans-LXB4). Results of the present study indicate that porcine leukocytes can generate lipoxin B4 and its isomers from endogenous sources of arachidonic acid. Moreover, they suggest that certain PLA2 isoenzymes may stimulate the formation of lipoxins and related compounds.