LEUKOTRIENE-B(4) OMEGA-HYDROXYLASE ACTIVITY IN POLYMORPHONUCLEAR LEUKOCYTES FROM PATIENTS WITH INFLAMMATORY BOWEL-DISEASE

Omega-oxidation is regarded as the major pathway for the catabolism of leukotriene B4 (LTB4). To determine how LTB4 omega-hydroxylase is mod ulated in inflammatory bowel disease, we investigated the kinetic char acteristics of this enzyme in 10 patients with Crohn's disease (CD), n ine with ulcerative colitis (UC) and eight healthy control subjects. A fter incubating polymorphonuclear leukocytes with various concentratio ns of H-3-labeled LTB4, omega-oxidation products were serapated by hig h performance liquid chromatography (HPLC) and the radioactivity was m easured by a liquid scintilation counter. The apparent Vmax values wer e significantly higher in both disease than in healthy control subject s, although the difference between CD and UC was insignificant. There was no difference in the apparent Km values. And the Vmax/Km ratios of patients with CD were significantly higher than that of healthy contr ol subjects. It is suggested that LTB4 metabolism is activated in infl ammatory bowel disease (IBD) and that the modulation of this enzyme ac tivity has an important role in the pathogenesis of inflammatory bowel disease.