Cell types of endocrine pancreas by immunoelectron microscopy

Abstract

The first light microscopic studies using differential staining have established that the endocrine pancreas (also named islets of Langerhans) of a large number of mammals contained at least three different cell types (1,2). In the early days of electron microscopy, two cell types, the alpha and the beta cell, were identified by using ultrathin sections adjacent to thick sections specifically stained for light microscopic investigation (3–5). Later on, the delta cell was identified on the basis of its location in the islet and on the ultrastructural characteristics of its secretory granules which appeared different from those of alpha and beta cells (6–10). In the seventies, the rapid development of immunocytochemical techniques, especially those applied to the ultrastructural localization of antigens (11), as well as the discovery of new pancreatic hormones (12, 13), has largely contributed to an easier identification of the cell types and organelles containing the different hormones of the endocrine pancreas. In this chapter, we have summarized what is presently known about the identification and classification of the different cell types of the mammalian endocrine pancreas.