Effects of staurosporine, genistein and pertussis toxin on PMA-induced superoxide generation and degranulation in neutrophils were investigated. Their effects were also examined in C5a-stimulated superoxide generation. PMA-induced superoxide generation was inhibited by staurosporine but was not affected by pertussis toxin. Genistein enhanced the stimulatory effect of PMA in a dose dependent fashion. C5a-induced superoxide generation was inhibited by staurosporine, genistein and pertussis toxin. An NADPH oxidase system of resting neutrophils was activated by PMA, and the stimulatory effect of I~IA was inhibited by staurosporine but was not affected genistein and pertussis toxin. The activity of NADPH oxidase in the membrnne fraction of PMA-activated neutrophils was not affected by staurospodne and genistein. PMA-induced acid phosphatase release was inhibited by staurospodne and genistein, whereas the effect of pertussis toxin was not detected. These results suggest that the role of protein tyrosine kinase in neutrophil activation mediated by direct activation of protein kinase C may be different from receptor-mediated activation. The action of protein kinase C on the respiratory burst might be affected by the change of protein tyrosine kinase activity.