Mitochondrion-secretory granules complexes in pancreatic islet B-cells

Mitochondrion-Secretory Granule Complexes (MSGC) are present in rodent pancreatic islet B-cells, characteristically showing fusion of mitochondria and secretory granules, absence of granule membrane and external mitochondrial membrane at place of contact, often invagination of internal mitochondrial membrane at place of contact forming an electron lucent space directly continuous with the "halo" of the secretory granules, and occurrence of potassium pyroantimonate precipitates in either or both of mitochondria and secretory granules. The MSGC are believed to possess functional significance, possibly playing a role in translocation of ions between mitochondria and secretory granules in the B-cells.