AMYLIN-CONTAINING CELLS IN THE GASTRO-ENTERO-PANCREATIC (GEP) ENDOCRINE SYSTEM OF THE RAT AND HUMANS

AN IMMUNOHISTOCHEMICAL STUDY

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Amylin (Islet Amyloid Polypeptide, IAPP)-containing cells were immunohistochemically investigated in the pancreas and gastrointestinal tract of the rat and humans with reference to its co-existence with gut hormones. Immunoreactivity for amylin was found in pancreatic islets and in endocrine cells dispersed in the pyloric antrum. The major population of islet cells in the rat was immunoreactive for amylin, being identified as B and D cells. Weak immunoreactivity for calcitonin gene-related peptide (CGRP) was recognizable in the rat B cells as reported previously. However it disappeared when the CGRP antiserum was pretreated with amylin, suggesting that the CGRP antiserum might have cross-reacted with an amylin molecule contained in the B cells. Amylin-immunoreactive cells in the pyloric antrum corresponded to gastrin (G) cells in rats and also in humans. This is in contrast to a previous study showing the amylin immunoreactivity in non-G cells of the human pyloric antrum. The amylin immunoreactivity in the pancreatic islets was recognized in rat fetuses, whereas in the pyloric G cells it first appeared on day 28 after birth. Immunohistochemistry at the electron microscopic level demonstrated that amylin was localized in the secretory granules of B, D and G cells.