Endotoxin induces eosinophil accumulation in the rat pleural cavity

Changes in eosinophil counts after intrathoracic (it) injection of endotoxin (LPS) were investigated in Wistar rats (150-180 g). Increasing doses of endotoxin (62.5-500 ng/cavity) induced a dose-dependent increase in the number of eosinophils recovered from the rat pleural cavity 24 h later. The eosinophilia was apparent within 24 h, peaked within 48 h (from 0.76 +/- 0.12 to 3.68 +/- 0.51 eosinophils x 10(6)/cavity, P less than 0.001) and returned to basal levels 120 h after the it injection of endotoxin (250 ng/cavity). Endotoxin (3 ng-4 micrograms/ml) failed to attract eosinophils in vitro under conditions in which PAF-acether induced a dose-related response. These findings indicate that endotoxin-induced eosinophil migration in vivo is mediated by a secondary mechanism.