Phospholipase A2 and arachidonic acid: a common link in the generation of the eosinophil chemotactic factor (ECF) from human PMN by various stimuli.

An eosinophil chemotactic factor (ECF) of low molecular weight can be generated and released from human polymorphonuclear neutrophils by the calcium ionophore, phagocytosis of zymosan particles, arachidonic acid, and phospholipase A2. Since the activation of cells by the ionophore and during the phagocytic event leads to phospholipid turnover, with the subsequent generation of arachidonic acid, it is reasonable that phospholipase A2 represents the common link for ECF production. The kinetics of ECF release by phospholipase A2 is similar to the pattern observed with the various stimuli. After a rapid rise in activity a decline occurred at later times of secretion, suggesting a mechanism of inactivation. During subcellular fractionation of cells an ECF-generating component was enriched in the 200,00 g supernatant fraction, which represents the cytosol. Addition of arachidonic acid or phospholipase A2 induced ECF generation. On gel filtration analysis the ECF-generating component revealed a molecular weight of about 80,000 daltons. It is suggested that this component represents a lipoxygenase.