ISLET AMYLOID POLYPEPTIDE IN THE GUT AND PANCREAS - LOCALIZATION, ONTOGENY AND GUT MOTILITY EFFECTS

The occurrence of islet amyloid polypeptide (IAPP) in the gut and panc reas of several species and during ontogeny of the rat, was studied us ing immunocytochemistry. Effects of IAPP on rat ileal smooth muscle we re assessed in vitro. Islets of most, but not all, species examined, d isplayed IAPP in insulin cells and, in some species, also in somatosta tin-and peptide YY (PYY)-containing cells. In the gut, expression of I APP varied among species; when present, IAPP was most abundant in the proximal part and co-localized with somatostatin, PYY, gastrin/cholecy stokinin, enteroglucagon or serotonin. IAPP was first demonstrated at embryonic day 12 and 16 in islet and gastrointestinal endocrine cells, respectively. IAPP relaxed grit muscle and reduced electrical field s timulation-evoked contractions, presumably by inhibiting acetylcholine release. Thus, IAPP expression in islets is consistent with an import ant role for IAPP in fuel metabolism; the gastrointestinal expression and motor effects of IAPP suggest that IAPP may modulate gastrointesti nal function. (C) 1997 Elsevier Science Inc.