Gastro-entero-pancreatic (GEP) endocrine system of the flatfish, Paralichtys olivaceus: an immunocytochemical study.

The localization of the gastro-entero-pancreatic (GEP) endocrine cells in the flatfish, Paralichtys olivaceus was examined using immunocytochemical methods. The Brockmann body of the flatfish included a large principal islet and a smaller islet. Three types of endocrine cells, i.e., insulin-, glucagon- and somatostatin-immunoreactive cells were found in both islets. Pancreatic polypeptide (PP)-immunoreactive cells were restricted to the periphery of the smaller islet. In the digestive tract, somatostatin cells occurred only in the stomach. The pyloric appendages contained cells reactive simultaneously to cholecystokinin (CCK) antiserum and to gastrin antiserum, whereas the middle portion of the intestine contained cells reactive only to the CCK antiserum. The intestinal endocrine cells showing N-terminal glucagon-immunoreactivity were also reactive to a glicentin antiserum.