[Histologic characterization of late asthmatic response in guinea pigs]

We examined lung tissues in a guinea pig model actively sensitized by inhalation of aerosolized ovalbumin (OA) and found reproducible late bronchial responses (LBR) 7 h and 24 h after OA challenge. Light microscopic examination revealed bronchoconstriction, damage to the epithelium, eosinophil infiltration in both the epithelium and subepithelium, retention of mucous in the pulmonary bronchial lumens and a decrease in the mucous content of Periodic Acid-Schiff (PAS) stain positive cells in the bronchial epithelium in LBR. An increase in the number of PAS-stain positive cells of in the bronchial epithelium was also observed in LBR. Electron microscopic examination revealed eosinophil migration around mast cell at 7 hs after OA challenge. Two different mechanisms of degranulation of eosinophil specific granules were observed in LBR. In one mechanism, the granule core changes after its matrix has changed. In the other mechanism, the granules were exocytosed as a whole, accompanied by the cell membrane and densely clumped chromatin, suggesting burst of eosinophil.