AMYLIN-IMMUNOREACTIVITY IS CO-STORED IN A SEROTONIN CELL SUBPOPULATION OF THE VERTEBRATE STOMACH AND DUODENUM

Amylin (or islet amyloid polypeptide) is a 37 amino acid peptide origi nally isolated from amyloid deposits in the pancreas of non-insulin de pendent diabetic patients. It has already been immunohistochemically l ocalised within the B and D cells of pancreatic islets and in endocrin e cells of the rat and human stomach and duodenum. In this phylogeneti c study, a polyclonal antiserum raised against the carboxy-terminal tr idecapeptide amide of human amylin was used to demonstrate and examine the distribution of amylin-immunoreactivity in the stomach and duoden um of various vertebrate species. Except for fish, gastrointestinal tr acts of all the species studied contained amylin-immunoreactive endocr ine cells. They were located chiefly in the lower half portion of the distal gastric body and pyloric glands, and in the lining epithelium o f the duodenal villi and crypts. Many cells were elongated, triangular or oval, and had a cytoplasmic process that extended from the cell ba se along the basement membrane, Others had a bipolar feature that gave them a so-called ''open'' appearance. Double and triple staining proc edures on the same tissue section showed that almost all the amylin-im munoreactive cells present in the gastroduodenal region also co-stored serotonin and chromogranin A, and displayed argyrophilia in Grimelius impregnation. On the other hand, almost all the serotonin-immunoreact ive cells of this region co-stored amylin, whereas those in more dista l gut regions did not. This finding suggests that those amylin-contain ing cells correspond to a subtype of gastroduodenal serotonin cells.