Types of the secretory cells in the pancreatic islands of some vertebrates]

Three types of secretory cells -- B, A and D were found in the pancreatic islets of the frog, turtle, crucian, rat and cat by the method of electron microscopy. The fine structure of secretory granules is a basis for identification of the endocrine cell types. The structure of the insuline granules is changed more markedly in the evolution process while the granules of A and D cells have a similar structure in the vertebrates under study.