LEUKOTRIENE A(4), AND NOT LEUKOTRIENE B-4, IS THE MAIN 5-LIPOXYGENASEMETABOLITE RELEASED BY BOVINE LEUKOCYTES

The production of leukotriene A(4) (LTA(4))-derived metabolites, analy sed by RP-HPLC, mas studied in purified bovine polymorphonuclear leuko cyte (PMNL) preparations and in PMNL-platelet coincubations after chal lenge with the calcium ionophore A23187, Tbe results obtained show tha t in bovine PMNL LTB(4) represents the main LTA(4) metabolite, When wa shed platelets were added to PMNL, LTC(4) was the main enzymatic metab olite observed, indicating a substantial transfer of PMNL-derived LTA( 4) to platelets, The synthesis of LTC(4) was accompanied by a signific ant decrease in LTB(4), suggesting that a quota of the LTB(4) synthesi zed in PMNL preparations is the result of transcellular metabolism of released LTA(4) by neighbouring PMNL. Reduction of PMNL-PMNL interacti ons through dilution of cell incubates allowed us to estimate that mos t of the leukotriene A(4) synthesized by PMNL is indeed released from the cell, LTA(4), and not LTB(4), represents the main 5-lipoxygenase m etabolite released by bovine PMNL.