Cysteine proteinases in bronchoalveolar epithelial cells and lavage fluid of rat lung.
We examined the presence of cathepsins B, H, and L in bronchoalveolar epithelial cells, including alveolar macrophages, and in bronchoalveolar lavage fluid (BALF), using immunocytochemistry and immunoblotting. By light and electron microscopy, immunoreactivity for cathepsins B, H, and L was detected in lysosomes of ciliated and non-ciliated epithelial cells of bronchi and bronchioles, and in macrophages. Immunodeposits for cathepsin H only were demonstrated in lamellar bodies of Type II alveolar epithelial cells, suggesting the cosecretion of surfactants and cathepsin H from the cells into the alveolar space. By immunoblotting, cathepsins B and H were found to be present in BALF. To further investigate the origin of these enzymes in BALF, alveolar macrophages obtained from BALF were cultured for 6 hr in a serum-free medium. Immunoblotting revealed that protein bands corresponding to the pro-form and mature form of cathepsin B and the mature form of cathepsin H were present in the culture medium. From these results, the presence of cathepsins B and H in BALF can be explained by the fact that cathepsin B is secreted from alveolar macrophages and cathepsin H is secreted mainly with surfactants from Type II cells and also from macrophages.[1]References
- Cysteine proteinases in bronchoalveolar epithelial cells and lavage fluid of rat lung. Ishii, Y., Hashizume, Y., Watanabe, T., Waguri, S., Sato, N., Yamamoto, M., Hasegawa, S., Kominami, E., Uchiyama, Y. J. Histochem. Cytochem. (1991) [Pubmed]
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