Distribution of gastrin and secretin immunoreactive cells in the gut of an Indian Skipper frog, Euphlyctis cyanophlyctis (Schneider): An immunohistochemical study

Abstract

The present investigation deals with the identification, localization, and mapping of gastrin and secretin-producing endocrine cells in different regions of the alimentary canal of Euphlyctis cyanophlyctis (Schneider) through the immunohistochemical (IHC) technique. G-IR (gastrin immunoreactive) cells of both the open and the closed types were present abundantly in the gastric mucosa of the pyloric region, in comparison to that of the fundic region. The open type of cells had long protoplasmic extensions reaching up to the lumen, suggesting the lumone concept of gastrin secretion. While the closed types were restricted towards the basal region of the mucosa and occurred in polymorphic forms ranging from rounded, oval, pyramidal, to amoeboid appearance. The closed type of G-IR cells was recorded in the duodenal mucosa, revealing the source of intestinal gastrin. Thus, suggesting a hormone-lumone-parahormone concept of gastrin secretion. The S-IR (secretin immunoreactive) cells were localized in both the duodenal and ileum regions of the alimentary canal. Comparatively, the number of S-IR cells was abundant in the duodenal mucosa, with respect to the ileum region. In the myenteric plexus of the ileum region, abundant secretin immunoreactivity was recorded, indicating that secretin not only acts as a hormone but also acts as a neuromodulator. All the S-IR cells were of the closed type, and no open type has been observed in the present study. The immunohistochemical study of amphibian gut endocrine cells provide valuable insights into gut health, gastrointestinal disorders, and the physiology and phylogeny of gut endocrine cells, thereby contributing to a deeper understanding and reframing of amphibian gut biology.