Morphology of the pancreatic endocrine A and B cells in normal‐ and epinephrine‐treatedTriturus carnifex

The endocrine islets of Triturus carnifex consisted mainly of a core of B cells and a peripheral mantle of A cells. A rich supply of nerve terminals innervated the endocrine cells. The A and B cells showed a cytoplasm filled with secretory granules, glycogen, lipid droplets, microtubules and microfilaments, a well‐developed RER, and Golgi. To study the hormonal control of the secretion and the eventual morphological changes of the cells evoked by the hormonal stimulus, the newts were treated with 100 and 3×100 ug of epinephrine that caused dose‐dependent variations in pancreatic endocrine cells. B cells were inhibited by the lowest and stimulated by the highest doses, whereas A cells were always stimulated.