Immunohistochemical localization of two types of carbonic anhydrase isozymes in oncocytoma and oncocytic epithelial cells

An immunohistochemical study was performed on the localization of carbonic anhydrase isozymes I and II (CA I and CA II, respectively) in oncocytoma and oncocytic epithelial cells. Tumors examined were those deserved to be called oncocytomas such as Warthin's tumor, Hürthle cell tumor of the thyroid gland and renal oncocytoma. In addition, the same immunostaining was done on several pathologic lesions, accompanying moderate number of cells similar in tinctorial character to oncocytes, such as some type of adenoma of the thyroid gland, endometrial hyperplasia, endometriosis and so on. Specific antibodies against CA I and CA II prepared from human erythrocytes were converted into Fab' fragment and labeled with horseradish peroxidase. In each tissue sample, the majority of oncocytes or oncocytic epithelial cells showed a tendency to exhibit an immunostaining reaction for CA I and II intenser than that of adjacent original normal epithelium from which they might derive. To the authors' knowledge, no reports have been appeared on biological relevance of an increased activities of carbonic anhydrase in conjunction with a large number of mitochondria appearing in such oncocytic cells. In the present study, it is revealed that the immunoreactivities of CA isozymes increased in oncocytes as the number of mitochondria increased, suggesting that oncocytes have a high level of carbonic anhydrase for catalyzing the hydration of an increased amount of carbon dioxide generated chiefly via oxidative metabolism by mitochondria, the number of which is notably increased compensatorily for their deficient coupling of oxidative phosphorylation or other metabolic anomaly.