Metabolism of [1-14C]-arachidonic acid by cultured calf aortic endothelial cells: evidence for the presence of a lipoxygenase pathway.

Intact cultured calf aortic endothelial cells from a 10th-14th subculture rapidly metabolize exogenous [1-14C]-arachidonic acid by three different routes: i) incorporation into triglycerides and phosphilipids in a ratio of about 2:1, ii) formation of lipoxygenase metabolites (12-hydroxy-5,8,10,14-eicosatetraenoic acid) and iii) formation of cyclooxygenase metabolites (6-keto-PG F1 alpha and PG F2 alpha). From analyses by thin-layer chromatography and high-pressure liquid chromatography it was established that the main lipoxygenase metabolites in intact cells are 12-hydroxy-5,8,10,14-eicosatetraenoic acid and a compound proposed to be (a) dihydroxyeicosatetraenoic acid(s). In frozen and thawed cells the incorporation of arachidonic acid into cellular lipids is abolished, whereas the lipoxygenase pathway is strongly enhanced. Under these conditions the cells produce predominantly 15-hydroxy-5,8,11,13-eicosatetraenoic acid in addition to 12-hydroxy-5,8,10,14-eicosatetraenoic acid. The formation of lipoxygenase products was inhibited by heating the cells or by preincubation with nordihydroguaiaretic acid or BW 755 degrees C, whereas indomethacin was without effect. The formation of 12-hydroxy-5,8,10,14-eicosatetraenoic acid by intact cells was inhibited by 5,8,11-eicosatriynoic acid. Indomethacin and acetylsalicylic acid inhibited the formation of cyclooxygenase metabolites. 15Ls-hydroxy-5,8,11,13-eicosatetraenoic acid was incorporated into cellular lipids, but not dihydroxyeicosatetraenoic acids. Exogenous [3H]-labelled prostacyclin and TxB2 were not incorporated but were metabolized to less polar products.