Human monocytes maintained in culture acquire functional responsiveness to platelet-activating factor that is independent of increases in protein tyrosine phosphorylation

Abstract

1. Acute (day 0) stimulation with platelet-activating factor (PAF) did not elicit superoxide anion (O2-) generation from adherent monocytes. However by day 2 of culture, PAF induced an increase in O2- generation that was inhibited by pretreatment with the PAF receptor antagonist WEB 2086. 2. The lack of effect of PAF on O2- generation was not due to the absence of receptors, as PAF stimulated an increase in tyrosine phosphorylation and intracellular calcium ([Ca2+](i)) on both days 0 and 2 of culture. 3. Pretreatment with the protein tyrosine kinase inhibitor methyl 2,5-dihydroxycinnamate inhibited PAF-induced tyrosine phosphorylation; however, this inhibitor failed to inhibit PAF-induced O2..