An immunocytochemical study of regulatory peptides in the amphibian gastrointestinal tract

Abstract

Samples from the gastrointestinal tract of two urodele and eight anuran species were investigated by immunocytochemical methods for the presence of structures immunoreactive with a range of antisera raised to the mammalian regulatory peptides. The regulatory peptides involved were gastrin, cholecystokinin, motilin, secretin, gastric inhibitory polypeptide, pancreatic glucagon, enteroglucagon, glicentin, neurotensin, somatostatin, pancreatic polypeptide, vasoactive intestinal polypeptide, substance P, Met-enkephalin, bombesin, and β-endorphin. In the majority of the species investigated, immunoreactive epithelial endocrine cells were demonstrated with the antisera to somatostatin, gastrin, enteroglucagon, and neurotensin. Motilin-containing cells were observed in a single species, Ambystoma mexicanum. Of the peptides detected within the mammalian innervation, vasoactive intestinal polypeptide, substance P, Met-enkephalin, and β-endorphin immunoreactive nerve fibres were seen. The distribution of the immunoreactive nerves differed significantly with species. Bombesin immunoreactivity was not seen within the innervation, although a population of endocrine cells was detected within the corpus of several species. No immunoreactivity was observed with the antisera to secretin, gastric inhibitory polypeptide, or pancreatic polypeptide in the species investigated.