Immunohistochemical localization of pyruvate carboxylase and carbamyl-phosphate synthetase I in normal and neoplastic human pancreatic tissues.

Abstract

It has been suggested that pyruvate carboxylase (PC) and carbamyl-phosphate synthetase I (CPS I) might be colocalized with carbonic anhydrase V (CA V), which is generally considered to provide HCO3- ions for PC and CPS I. To examine the immunohistochemical staining of endogenous biotin; of three mitochondrial biotin-binding enzymes (namely, PC, CPS I, and propionyl CoA-carboxylase); and of cytosolic acetyl CoA-carboxylase in pancreatic tissues. Immunohistochemical analysis was performed on 23 samples of normal pancreas and 63 samples of neoplastic pancreatic tissues. It was found that the distribution of PC, CPS I, and endogenous biotin was not related to that of CA V but was similar to that of CA II in normal centroacinar cells, intercalated duct cells, and intralobular duct cells. In addition, PC was detected unexpectedly in delta-cells of islets. It seems likely that CA II plays a major role in the secretion of NaHCO3 into the pancreatic juice. Hence, it is possible that PC and CPS I in the centroacinar cells, intercalated duct cells, and intralobular duct cells are strongly activated and might use HCO3- ions provided by CA II and not by CA V. Among the pancreatic neoplasms examined, ductal adenocarcinomas exhibited significantly elevated immunoreactivity specific for the four biotin-binding enzymes.