Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Germany. monika.wimmer@anatomie.med.uni-giessen.de
The secretory vesicles of some cells of the islets of Langerhans of the pancreas contain high amounts of immunoreactive tyrosine phosphatase of the PTP1B/TCPTP subfamily. The cells are located in the peripheral parts of the islets and were identified as glucagon- and pancreatic polypeptide-forming cells. The tyrosine phosphatase is also enriched in some of the somatostatin-producing cells but is not elevated either in insulin-producing B-cells or in the exocrine pancreas. Virtually the same patterns were found in pancretic tissues of rats, guinea pigs, pigs, and mice. High levels of detergent-soluble tyrosine phosphatase were measured in the particular fraction of pancreatic islets with a substrate preferred by PTP1B/TCPTP-type protein tyrosine phosphatases.