Stimulation of human leukocyte degranulation by leukotriene B₄ and its ω‐oxidized metabolites

and adhesion to post- capillary venules [3]. In [4-61 LTB., was suggested to be a weak stimulator of polymorphonuclear leuko- cyte (PMNL) degranulation. However, it is now clear that previous purification procedures for biosyntheti- tally prepared LTB4 were inadequate. The newly discovered LTB4 isomer, SQ,12Q-DHETE, co-chro- matographs with LTB4 in the reverse phase high- pressure liquid chromatography (HPLC) systems commonly used [7]. As a consequence, earlier studies probably tested preparations which contained a mix- ture of both isomers with the non-leukotriene product predominating. Therefore, we have investigated the role of LTB4, SQ,12(S)-DHETE and their o-oxida- tion products (fig.1) [8] in leukocyte degranulation in vitro. In addition, the activity of the non-enzymati- tally formed LTB4 isomers was investigated. Cytochalasin B, phenolphthalein glucuronic acid, and dried