[Epithelial permeability study of the bronchi in chronic bronchitis using an electron-dense tag]

An electron dense tracer, horseradish peroxidase (HRP), treated with DAB-H2O2 for electron histochemical demonstration of peroxidase was used in an effort to find out whether or not the human bronchial epithelium was permeable to some macromolecules in chronic bronchitis. The biopsy specimens obtained from 5 patients at bronchoscopy and cultured in a medium with 2% HRP for 1-6 hours showed the reaction product to be distributed within intracellular spaces of the epithelium as well as in some vesicles and vacuoles of the apical portion of the ciliated cells. When 2% HRP solution was topically applied on the bronchial epithelium surface of a narcotized patient for 10 min followed by biopsy of this part of the epithelium fixation and treatment for HRP demonstration, electron dense precipitates were identified only within some intercellular spaces. It is suggested that some intercellular contacts of the bronchial epithelium in chronic bronchitis are permeable to macromolecules, and that the ciliated cells of the bronchial epithelium are capable of endocytosing some macromolecules from the surface of the mucosa.