Chromostatin, a chromogranin A-derived bioactive peptide, is present in human pancreatic insulin (beta) cells

Chromogranin A (CGA) is a secretory protein present in the adrenal medulla and in a variety of endocrine organs. This protein may serve as precursor for pancreastatin (PST) and for other biologically active peptides. Recently, chromostatin (CST), a CGA derivative, has been identified that possesses high biological activity. The cellular distribution of CST in various endocrine organs is completely unknown. Using immunohistochemistry on plastic sections, we investigated the occurrence and cellular distribution of CST, PST, and CGA in human endocrine pancreas of healthy and diseased states and in the adrenal medulla. In the normal and diabetic pancreas, CST immunoreactivity was localized exclusively in beta cells, which were mostly unreactive for PST and CGA. Both latter peptides were confined mainly to glucagon (alpha) cells. Insulinoma cells displayed strong insulin, PST, and CGA immunoreactivities, but they were faintly immunoreactive for CST or unreactive. Adrenal chromaffin cells exhibited strong immunoreactivity for CGA but lacked CST and PST immunoreactivities. Based on the peculiar distributive pattern of CST, PST, and CGA, we suggest that CGA is differentially processed in chromaffin and islet tissues and in insulinoma cells. The unique cellular localization of CST in the endocrine pancreas of normal and pathological conditions may indicate that CST is involved in beta-cell function.