Immunohistochemical localization of carbonic anhydrase isoenzymes in the human pancreas

Carbonic anhydrase exists in two main forms (isoenzymes C and B) which differ from each other immunologically and in their level of activity, for instance. It is important to know the location of the enzyme in order to obtain a better understanding of its physiologic role. Since previous histochemical studies using metal salt methods for the demonstration of carbonic anhydrase activity have produced unsatisfactory results, the immunoperoxidase technique is applied here to investigate the location of the isoenzymes of carbonic anhydrase in the human pancreas. Isoenzyme C was localized specifically in the epithelium of the intra- and interlobular ducts, whereas the isoenzyme B was found only in the erythrocytes of the tissue. No carbonic anhydrase was found in the islets of Langerhans. The immunohistochemical results were confirmed by double immunodiffusion, in which the pancreatic tissue fluid from the thawed frozen sections generated a strong precipitation line with the rabbit antiserum against isoenzyme C and a very weak precipitation with the antiserum against the isoenzyme B.