Leukotriene B4 metabolism in human leukocytes: fact or artefact?

The object of this study was to investigate the importance of omega oxidation in regulating leukotriene B4 (LTB4) levels in man. In human polymorphonuclear leukocytes metabolism of LTB4 was rapid but was critically dependent on PMN number: greater than 1.5 X 10(6) PMN/ml were required. Metabolism of LTB4 was blocked in the presence of plasma. In whole blood and in PMN-rich rheumatoid synovial fluids no significant metabolism of LTB4 was detected within 30 min at 37 degrees C. We conclude that LTB4 metabolism at inflamed sites will be regulated both by cellular content and the degree of plasma exudation. In most pathological conditions rapid exchange with the micro-vasculature will be more important than metabolism in limiting LTB4 levels.