Immunohistochemical localization of insulin-like materials in antral gastric mucosa and intestinal epithelial cells of the turtles Chrysemys dorbigni and Phrynops hilarii.

Immunoreactive insulin was demonstrated immunohistochemically with antibodies to human and porcine insulin by the avidin-biotin-peroxidase complex method in open-type gastrointestinal cells from sections of the antral stomach and of the upper, middle and lower intestine of the turtles Chrysemys dorbigni and Phrynops hilarii. In both species the concentration of cells positive for insulin-like material was higher in the gastric antrum than in the gut. The localization of insulin-like material in gastrointestinal mucosal cells of turtles is an unusual finding among vertebrates, because the insulin-containing cells migrate from the mucosal epithelium of the intestine early in vertebrate evolution to the acinar pancreas. The chemical nature of the gastrointestinal insulin-like material and its physiological role remain to be determined.