Rat Islet Amyloid Polypeptide (IAPP): Isolation and Sequence Determination, Immunohistochemical Study, and its Secretion from Pancreas

Abstract

We isolated and identified IAPP[1-37] and IAPP[19-37] in normal rat pancreas by sequence analyses. Regional distribution and molecular forms of rat IAPP were studied by a highly sensitive and specific radioimmunoassay (RIA) for the peptide. IAPP[19-37], accounting for 57% of IAPP- immunoreactivity in rat pancreas, is a major molecular form of rat IAPP moiety. A large amount of IAPP (328.5 ± 25.0 pmol/g wet weight) was found in rat pancreas and the peptide was also detected in pyloric antrum of stomach, duodenum, jejunum, ileum, and colon at 0.1-0.8% of the level of pancreas. IAPP was immunohistochemically observed in B cells in the islets and the lower portion of the mucosa of gastrointestinal tract of the rat. IAPP was secreted from perfused rat pancreas in response to glucose. The distribution and secretion of IAPP suggest a possible endocrine or paracrine function in pancreas and gastrointestinal tract.