STIMULATED EOSINOPHILS AND PROTEINASES AUGMENT THE TRANSEPITHELIAL FLUX OF ALBUMIN IN BOVINE BRONCHIAL-MUCOSA

1 The apical to basolateral transmucosal flux of albumin has been meas ured in isolated sheets of bovine bronchial and tracheal mucosa. Under resting conditions the net unidirectional flux in the bronchial mucos a was not significantly different from that measured previously for th e basolateral to apical vector. In contrast, the apical to basolateral flux in the tracheal mucosa was significantly lower than that measure d in the opposite direction. 2 Addition of guinea-pig peritoneal eosin ophils to the apical side of the tissues had no significant effect on the transmucosal flux of albumin in either the bronchial or tracheal m ucosa. 3 When eosinophils were stimulated with the ionophore A23187 or by opsonic adherence to tissues treated with a guinea-pig anti-bovine airway epithelium antibody, the bronchial mucosal sheets that had bee n exposed showed a significant increase in the transmucosal flux of al bumin. However, tissues from the tracheal mucosa were resistant to the effects of stimulated eosinophils. 4 Histologically, sheets of mucosa from bovine main bronchi that had been exposed to stimulated eosinoph ils were characterized by epithelial injury consisting of loss of colu mnar epithelium from the underlying basal cell layer and biomatrix. Mu ch less evidence of cellular injury was observed in tracheal tissues. 5 Bacterial collagenases applied to the apical side of the sheets were shown to increase the permeability of the bronchial mucosa to albumin and to produce histological changes that had similarities with the pa ttern of damage produced by stimulated eosinophils. 6 These observatio ns demonstrate that the ability of eosinophils to injure the bronchial mucosa is independent of the side of the tissue on which they are pre sent. Furthermore, key aspects of the injury process may be reproduced , at least in part, by metalloproteinases.