Distribution and Morphology of Ghrelin-Immunopositive Cells in the Pancreas of the African Ostrich

Ghrelin, the endogenous ligand for the growth hormone secretagogue receptor, has been identified in the pancreas of many vertebrates. While ghrelin has been found in the cerebellum and gastrointestinal tract of African ostrich chicks, little is known about its distribution in the pancreas of the African ostrich. In the present study, the distribution and morphological characteristics of ghrelin-immunopositive cells in the African ostrich pancreas were investigated using immunohistochemistry. Our results indicate that the pancreas is divided into two sections: the exocrine and endocrine portion. The exocrine portionis comprised of peripheral gland cells and centroacinar cells; the endocrine portion consists of islet cells. Ghrelin-immunopositive (ghrelin-ip) cells were found in both the pancreatic exocrine portion and islets. The greatest number of ghrelin-ip cells was found in the islets, and the cell density decreased gradually from the pancreatic islets to the extrainsular regions. The distribution of ghrelin-ip cells was observed mostly at the periphery of the islet, a few ghrelin-ip cells were found in the central portion of the pancreatic islets. The ghrelin-ip cells were fusiform or irregular polygons, and their cytoplasm was stained intensely. These results demonstrate the presence of ghrelin-ip cells in the pancreas of the African ostrich. Thus, it is speculated that ghrelin may have a physiological function in the pancreas.