PANCREATIC ENDOCRINE-CELLS IN BUFO-BUFO - IMMUNOCYTOCHEMISTRY AND ULTRASTRUCTURE

The endocrine pancreas of the toad consists of rounded islets of vario us sizes embedded in the exocrine tissue. Isolated cells are also pres ent. At least 4 types of endocrine cell are distinguishable by shape, size and electrondensity of the secretory granules as well as by their immunoreactivity with different antisera: insulin, somatostatin, panc reatic polypeptide, and glucagon cells. Insulin cells can be divided i nto 2 types according to their cytoplasmic electrondensity. Colocalisa tion of different hormones in the same cell is rarely observed. The cl ose contact between endocrine and exocrine cells and the scarcity of n erve supply is indicative of a paracrine control of hormone secretion.