Immunohistochemical study of endocrine cells in the gastrointestinal tract of the barking deer, Muntiacus muntjak

The morphology, distribution and relative frequencies of endocrine cells in the gastrointestinal tract of the barking deer (Muntiacus muntjak) were investigated. The immunohistochemical method employed used seven types of antisera against chromogranin, serotonin, gastrin, cholecystokinin, somatostatin, glucagon and insulin. Chromogranin and serotonin immunoreactive (IR) cells were found throughout the gastrointestinal tract. Conversely, gastrin-IR cells were only found in the oxyntic gland, pyloric gland and duodenum, while cholecystokinin-IR and somatostatin-IR cells were detected in the oxyntic gland, pyloric gland and small intestines. Somatostatin-IR cells were also seen in the caecum. Glucagon-IR cells were found in all parts of the gastrointestinal tract apart from the colon and rectum. No insulin-IR cells were found in the gastrointestinal tract of this species. The cells in the small intestine were generally spindle shaped with long cytoplasmic processes ending in the lumen (open type), while in the stomach and large intestine, they were occasionally round or spherical in shape (closed type). An uncommon distribution pattern of endocrine cells in the gastrointestinal tract of the barking deer was noted for cholecystokinin- and glucagon-IR cells.