Immunohistochemical study of the endocrine cells in the pancreas of the actinopterygian fishes (Actinopterigii)

The endocrine tissue in the pancreas of 10 actinopterygian fishes (Actinopterigii) species was investigated in present study. Insulin-immunoreactive cells in the most of the studied species (except A. Anguilla, E. Lucius, C. Carpio) had the spherical shape. Glucagon-immunoreactive and somatostatin-immunoreactive cells had the spindle shape with cytoplasmic processes in all species. Insulin-immunoreactive cells were located in the central region of the pancreatic islets; glucagon-immunoreactive cells were located on islet periphery in the most of these species. In A. ruthenus the islets contained only insulin-positive cells. In this case glucagon-and somatostatin-positive cells were distributed around the islets, single cells and small clasters were scaterred throughout the pancreas. In the islets of A. Anguilla, insulin-immunoreactive cells were found in the peripheral region, glucagon-immunoreactive cells were located in the central region. The observed polymorphism of the islets and endocrine cells can not be explained by feeding habits of fishes.