An immunohistochemical study of endocrine cells in the alimentary tract of the snake, Rhabdophis tigrinus tigrinus

The regional distribution and relative frequency of endocrine cells in the alimentary tract of the snake, Rhabdophis tigrinus tigrinus, were investigated by immunohistochemical method using 7 antisera. Chromogranin (Cg)-, glucagon-, somatostatin-, gastrin/cholecystokinin (Gas/CCK)-, serotonin-, bovine pancreatic polypeptide (BPP)-immunoreactive cells were identified in this study. Cg-immunoreactive cells were detected throughout the alimentary tract including the esophagus, with predominant frequency in the pylorus. Numerous immunoreactive cells were observed from the esophagus to the pylorus but a few cells were detected in the large intestine. Glucagon-immunoreactive cells were observed from the proximal portions to the distal portions of the small intestine. They were increased to the middle portions but thereafter decreased, and no cells were found in the terminal portions. Somatostatin-immunoreactive cells were restricted to the small intestine and these cells were decreased toward to distal portions of the small intestine. Gas/CCK-immunoreactive cells were detected in the pylorus and small intestine. They were most predominant in the pylorus and the proximal portions of the small intestine but thereafter decreased toward to the distal regions. Serotonin-immunoreactive cells were observed throughout the alimentary tract. They were most predominant in the pylorus and proximal portions of the small intestine but a few cells were observed in the large intestine. BPP-immunoreactive cells were restricted to the distal portions of the small intestine with rare frequency. No bombesin-immunoreactive cells were found in this study.