Distribution and relative frequency of immunohistochemically detected endocrine cells in the stomach of New Zealand White rabbit (Oryctolagus cuniculus)

Gastrointestinal (GI) endocrine cells produce many GI hormones that perform various physiological functions of the digestive system. We aimed to investigate the presence and distribution of immunoreactive (IR) endocrine cells to glucagon, somatostatin, cholecystokinin-8 (CCK-8), serotonin, secretin and histamine in the stomach of adult male New Zealand White rabbit (Oryctolagus cuniculus). For immunohistochemical staining, peroxidase anti-peroxidase (PAP) method was applied to stomach samples. Glucagon-IR cells of closed- and open type were found throughout all the stomach parts examined. Somatostatin-IR cells of closed- and open type in the cardiac and oxyntic glands were localized to deep portions of foveola gastrica. CCK-8 IR cells that were not observed in the cardia and fundus were mostly localized to the glands and lamina epithelialis in the pyloric part near the duodenum. Oval-shaped open and closed type serotonin-IR cells were mostly dispersed throughout the fundic and pyloric glands. Secretin-IR cells were rare in the pyloric and cardiac region although they were not observed in the fundic glands. Histamine-IR cells were rarely found in the cardia, fundus and pylorus. Our findings show that glucagon, histamine, somatostatin, secretin and serotonin might be produced by all the stomach regions while pyloric region had only CCK-8 IR. These distribution patterns also provide further evidence of species-specific differences, which might be important from the evolutionary aspect of the digestive tract in relation to evolutional niches and nutrient resources.