5-AMINOSALICYLIC ACID INHIBITS LEUKOTRIENE B-4 OMEGA-HYDROXYLASE ACTIVITY IN HUMAN POLYMORPHONUCLEAR LEUKOCYTES

omega-oxidation is regarded as the major pathway for the metabolism an d inactivation of leukotriene B-4 (LTB(4)). To investigate the action of 5-aminosalicylic acid (5-ASA) on LTB(4) omega-hydroxylase activity, we incubated human polymorphonuclear leukocytes (PMNLs) with H-3-labe led LTB(4) after pre-incubation with various concentrations of 5-ASA. omega-oxidation metabolites were separated by high performance liquid chromatography and each radioactivity was measured by a liquid scintil ation counter. LTB(4) omega-hydroxylase activity was inhibited by 5-AS A in a concentration-dependent fashion. The 50% inhibitory dose was ab out 50 mu mol/l, which is within the concentration range found in the colonic mucosa. Our findings may be valuable in elucidating the potent ially critical aspect of 5-ASA treatment in ulcerative colitis (UC).