Distribution of carbonic anhydrase isozyme III (CA-III)-positive cells in duct segments of the bovine submandibular gland

The distribution of carbonic anhydrase III isozyme (CA-III)-positive cells in bovine submandibular glands was studied by immunohistochemistry. CA-III showed strong immunoreactivity in basal cells and some lining cells of the intercalated ducts as well as in striated and interlobular ducts cells. No significant immunoreactivity could be found in other portions of the glands. Electron microscopically, the immunoreactive basal cells contained scattered tonofibrils in their cytoplasm. The distribution of CA-III suggests that the CA-III-positive basal cells may play a special physiological role, and that they do not only represent undifferentiated lining cells.