Expression of islet neogenesis-associated protein in islets of normal hamsters

Abstract

The aim of the present study was to test the possible presence and expression of islet neogenesis-associated protein (INGAP) in islet cells of normal adult hamsters. Pancreata from normal male Syrian hamsters were removed to perform the following studies. (i) Western blot analysis using the cytosolic fraction from homogenates of isolated islets, exocrine tissue and whole pancreas, and rabbit INGAP-specific antibody. (ii) Immunohistochemical identification of INGAP-positive cells in fixed sections of intact pancreata, fresh and 72 h cultured islets (isolated by collagenase digestion), and smears of exocrine pancreatic cells, using the same INGAP-specific antibody and streptavidin-biotin complex. (iii) RT-PCR using total RNA extracted from isolated islets and from exocrine tissue as template, and a specific pair of primers. (iv) Control of the sequence of the PCR products. INGAP protein was identified by Western blot in the cytosolic fraction of homogenates from fresh isolated islets, exocrine cells and whole fresh pancreas. INGAP-immunopositive cells were observed in duct, exocrine and islet cells in either fixed intact or digested pancreatic tissue. INGAP mRNA was identified in samples of total RNA from fresh and cultured isolated islets and from exocrine cells. Our data demonstrate that INGAP is present and expressed in islets and in exocrine pancreatic cells of normal hamsters. The ubiquitous localization of INGAP suggests its possible role in the physiological process of islet growth and its protective effect upon streptozotocin-induced diabetes.