[Characterization of 12-L-hydroxy 5, 8, 10-heptadecatrienoic acid produced by rat basophilic leukemia-2H3 cells]

14C- 12-L-hydroxy-5, 8, 10-heptadecatrienoic acid was produced by incubating the 10,000 x g supernatant of rat basophilic leukemia -2H3 cells with 14C-arachidonic acid in the presence of isoproterenol and hemoglobin. The Vmax was 125 p mol/min/2 x 10(7) cells and its Km value was 1.28 n mol, indicating the low synthetic activity even though a sufficient amount of the substrate was available. The synthesis was dose-dependently decreased by the addition of calcium ions and inhibited by ETYA and indomethacin but not by imidazol, suggesting that the production might be non-enzymatic break-down from PGH2.