Slide DMS143 [Pancreas, human, chrome alum hematoxylin & phloxine]. Distinguishing exocrine from endocrine parts of the pancreas is much easier in this slide. Study at higher magnification several islets. With this special stain glucagon-producing alpha cells stain red and insulin-producing beta cells stain blue. However, over the years the blue-staining of the beta cells has faded, but the alpha cells still appear red. Alpha and beta cells represent 20 and 75 percent of the islet cell population respectively. With more complex staining procedures two other cells can be identified: somatostatin-secreting delta cells and clear cells without stainable granules. Another islet cell type located preferentially in the head region secretes, in response to food ingestion, pancreatic polypeptide (PP), a hormone that stimulates gastric secretion while inhibiting bile secretion and intestinal peristalsis.

Schematic of islets of the pancreas: 1. exocrine acinar cells; 2. endocrine islet cells; 3. capillaries