Immunohistochemical localization of (neuro)peptide hormones in endocrine cells and nerves of the gut of a stomachless teleost fish, Barbus conchonius (Cyprinidae).

Abstract

Enteroendocrine cells containing glucagon-, substance P-, neurotensin- and VIP-like substances have been demonstrated immunocytochemically in the gut of Barbus conchonius. Mainly based on the distribution of the immunoreactive endocrine cells in this and a previous study, at least eight different enteroendocrine cell types appear to be present in this stomachless fish: C-terminal-gastrin-immunoreactive cells, predominantly present in the upper parts of the folds of the proximal part of the intestinal bulb. Metenkephalin-immunoreactive cells, basally located in the folds of the first segment. Pancreatic polypeptide (PP)-immunoreactive cells, mainly present in the first half of the first segment. Glucagon-like-immunoreactive (GLI) cells that are basally located in the folds of the first segment and that contain a different polypeptide (possibly glicentin) than pancreatic glucagon cells. Substance P-immunoreactive cells, present in the upper parts of the folds throughout the gut. C-terminal-neurotensin-immunoreactive cells, basally located in the folds throughout the first segment. Vasoactive intestinal polypeptide (VIP)-immunoreactive cells, present in small numbers in the proximal part of the intestinal bulb. Nonspecifically-immunoreactive cells, found throughout the intestinal bulb. Many VIP-immunoreactive nerves have been demonstrated in the smooth muscle layer and myenteric plexus of the gut; furthermore some of them are peptide histidine-isoleucine (PHI)-immunoreactive. Substance P-, somatostatin-, neurotensin- and met-enkephalin-immunoreactive nerves are also found. Thus, at least partial sequences of four different mammalian neuropeptide hormones (VIP, substance P, neurotensin, met-enkephalin) occur both in endocrine cells and enteric nerves of the gut of B. conchonius.