The regional distribution and frequency of endocrine cells in the Korean golden frog, Rana plancyi chosenica: an immunohistochemical study

Abstract

Distribution patterns and the relative frequency of different types of endocrine cells were demonstrated in the alimentary tract of the Korean golden frog (Rana plancyi chosenica Okada), which is known as a Korean endemic species, for the first time. The alimentary tract of the frog was divided into six portions from the esophagus to the rectum. Most endocrine cells were found in the epithelial lining and were generally spindle-shaped with cytoplasmic processes ending in the lumen (open-typed cell), whereas cells that were spherical in shape (close-typed cell) were occasionally found in mucosal glands. Endocrine cells were stained for the following regulatory peptides: Sp-1/chromogranin A (Cg A), serotonin, somatostatin, gastrin, cholecystokinin (CCK)-8, bombesin, pancreatic polypeptide (PP), and glucagon. Cells stained for Cg A and serotonin were present throughout the entire alimentary tract. Somatostatin-immunoreactive (IR) cells were detected throughout the entire alimentary tract except the rectum. Cells stained for gastrin and CCK-8 were restricted to the pylorus, duodenum, and ileum, whereas bombesin-IR cells were restricted to the esophagus, antrum, and pylorus. Glucagon-containing cells were located in the esophagus, antrum, pylorus, and duodenum. Most of the IR cells occurred with the highest frequency in the pylorus except for cells stained for somatostatin and bombesin, which showed the highest frequencies in the antrum and serotonin-IR cells, which showed in the duodenum, respectively. No PP-stained cells were detected in this study. In conclusion, distribution patterns and the frequency of these endocrine cells not only correspond well with other Salienta species but some deviating patterns were also observed.