Localization and release of lysozyme from ferret trachea: effects of adrenergic and cholinergic drugs

Lysozyme is a bacteriolytic enzyme found in respiratory tract fluid. In this study, immunocytochemistry was used to determine the cells of origin of tracheal lysozyme in the ferret. Lysozyme was found in secretory granules of serous but not mucous cells in the submucosal glands, and was absent from the surface epithelium, cartilage, and connective tissue. The exclusive presence of lysozyme in serous gland cells renders it useful as a biochemical marker of that cell type. Measurements of lysozyme assayed from the incubating medium indicated that bethanechol stimulated lysozyme release by 260 +/- 80.9% (mean +/- SE), phenylephrine by 80 +/- 16.4%, and terbutaline by 25 +/- 10.2%. Electron-microscopic and immunocytochemical analysis of incubated tissues revealed loss of serous granules and lysozyme immunoreactivity in response to the drugs. Atropine, propranolol, and phentolamine blocked the stimulatory effects of bethanechol, terbutaline, and phenylephrine, respectively. These findings establish the usefulness of lysozyme as a serous-cell marker and demonstrate that secretory responses of different magnitude are evoked by equimolar concentrations of alpha- and beta-adrenergic and cholinergic drugs.