Bradykinin induces eosinophil accumulation in the rat pleural cavity

Intrathoracic injections of bradykinin (1-100 micrograms/cavity) induced a dose-dependent increase in the number of eosinophils recovered from the rat pleural cavity 24 h later. Eosinophilia by bradykinin was preceded by a marked pleural neutrophil influx within 6 h and was absent only 72 h following stimulation. Bradykinin (10(-9)-10(-5) M) failed to induce in vitro eosinophil chemotaxis, indicating that its in vivo effect must be mediated by an intermediate messenger. BW 755C (25 mg/kg) and the more selective lipoxygenase inhibitor BW A4C (20 micrograms/cavity) suppressed the pleural eosinophilia induced by bradykinin (50 micrograms/cavity), whereas the platelet-activating factor (PAF)-acether antagonist BN 52021 was inactive. We conclude that bradykinin is able to attract eosinophil in vivo by a mechanism independent of PAF-acether and sensitive to the blockage of the lipoxygenase pathway.