Intermediate cells of the pancreas. 3. Selective autophagy and destruction of beta-granules in intermediate cells of the rat pancreas induced by alloxan and streptozotocin.

In addition to causing necrosis of β-cells, diabetogenic doses of alloxan or streptozotocin cause selective autophagy and destruction of β-granules in intermediate cells in the rat pancreas, thus providing evidence that these granules and those in the β-cells of the islet are identical. In acinar-β cells the autophagic vacuoles also contain small mitochondria similar to those that occur in islet endocrine cells. Apart from these effects, the cells remain structurally intact. These observations suggest that alloxan exerts a direct effect on the β-components of the β-granule-containing intermediate cells. The destruction of the β-granules in the acinar-β cell is sometimes accompanied by the appearance of α-granules in the same cells, thus presumably reflecting the increased demand for glucagon that occurs in experimental diabetes. Although intermediate cells containing α-granules are very uncommon in the normal rat pancreas, acinar-α and α-acinar cells occurred much more frequently after alloxan treatment. The presence of intermediate cells of the acinar-β type in normal rats and the observed change of acinar-β to acinar-α cells, or from α- to α-acinar cells after alloxan, indicates that some pancreatic cells possess a variable functional potentiality. The appearance of these cells after alloxan presumably reflects the altered metabolic state of the animal, and is not a manifestation of the transformation of one cell type into another.