Production of 15-hydroxyeicosatetraenoic acid by purified human eosinophils and neutrophils.

In the presence of high concentrations of exogenous arachidonic acid (greater than or equal to 10 microM), eosinophils produced 15-hydroxyeicosatetraenoic acid (15-HETE) in the absence of stimuli. The calcium ionophore A23187, as well as the chemotaxins used in this study--complement split product C5a, platelet-activating factor (PAF), and N-formyl-methionyl-leucyl-phenylalanine (FMLP)--failed to increase 15-HETE production, indicating that eosinophil 15-lipoxygenase is already active. Production of 15-HETE from eosinophils increased with increasing concentrations of arachidonic acid, exogenously added. Maximal 15-HETE production was observed to be 1111 +/- 380 ng per 10(6) eosinophils at the concentration of 100 microM of arachidonic acid. With low concentrations of exogenous arachidonic acid (below 2 microM), eosinophils were considered to incorporate exogenous arachidonic acid into their cell membrane, and did not produce 15-HETE. In contrast, 15-HETE formation in highly purified neutrophils (eosinophils less than 1%) was negligible compared with that in eosinophils (300-fold less), suggesting that 15-HETE-forming activity in granulocytes is derived from the eosinophil 15-lipoxygenase pathway and that neutrophils may lack 15-lipoxygenase activity.