Endocrine cells in the pyloric region of the Japanese quail (Coturnix coturnix japonica).

The endocrine cells of the pyloric region of the Japanese quail have been studied by light and electron microscopy. The quail pyloric region is a narrow circular zone (about 2 mm in width) between the gizzard and the duodenum. The endocrine cells are concentrated in this region, and they are represented by argyrophil cells. At least five types of endocrine cells are identified in this region by electron microscopy. Type I cells are characterized by having round and large granules (350--550 nm in diameter) whose contents are high to moderate in electron density. Type II cells are characterized by their round and medium-sized granules (250--350 nm) which possess a dense core and a clear halo. Type III cells are characterized by the presence of round and small-cored granules (150--250 nm). Type IV cells contain round and large granules (350--550 nm) of high to low electron density. Type V cells are identified by the occurrence of microfilaments and polymorphous granules of high electron density. All five cell types are recognized as open type cells. The type I, II and III cells are located mainly in the lower half portion of pyloric glands, and the other cell types are located only in the upper half portion of the glands. The type I and II cells are found much more frequently than other cell types. The relationships between the endocrine cells in the quail pyloric region and those of the mammalian digestive tracts were discussed.