Eosinophils play an important role in the pathogenesis of allergic diseases such 
as allergic asthma. Eosinophil migration in vitro can be divided into directed 
migration, or chemotaxis, and random migration, or chemokinesis. Here, we 
studied intracellular signals involved in eosinophil migration in vitro induced 
by platelet-activating factor (PAF) and interleukin-5 (IL-5), applying a Boyden 
chamber assay. Migration induced by PAF (10(-11)-10(-6) M) largely consisted of 
chemotaxis with some chemokinesis, whereas IL-5 (10(-12)-10(-8) M) induced 
chemokinesis only. Eosinophils were depleted from intracellular and 
extracellular Ca2+ to study the role of Ca2+ as a second messenger. Ca2+ 
depletion did not change PAF-induced chemotaxis, however, IL-5-induced 
chemokinesis was inhibited. Interestingly, PAF, but not IL-5, induced changes in 
[Ca2+]i. This rise originated mainly from internal stores. Inhibition of protein 
kinase A by H-89 and protein kinase C by GF 109203X had no effect on both forms 
of eosinophil migration. Addition of the protein kinase inhibitor staurosporine 
significantly inhibited IL-5-induced chemokinesis. Inhibition of tyrosine 
kinases by herbimycin A completely blocked IL-5-induced chemokinesis. PAF and 
IL-5-induced actin polymerization was studied to compare migratory responses 
with a migration-associated intracellular response. Ca2+ depletion significantly 
enhanced PAF-induced (10(-8) M) actin polymerization, whereas IL-5-induced actin 
polymerization was not influenced. Addition of staurosporine led to an increase 
in F-actin. Subsequent addition of PAF or IL-5 resulted in an additive increase 
in F-actin content. In summary, both forms of eosinophil migration are protein 
kinase A and protein kinase C independent. In contrast to PAF-induced 
chemotaxis, Il-5-induced chemokinesis was found to be completely Ca2+ and 
tyrosine kinase dependent.