Ravazzola M, Perrelet A, Unger R H, Orci L
Endocrinology. 1984 Feb;114(2):481-5. doi: 10.1210/endo-114-2-481.
Antigenic sites related to glucagon and glucagon precursors were characterized by ultrastructural immunocytochemistry in secretory compartments of the pancreatic A-cell, namely Golgi cisternae, condensing granules in Golgi cisternae, coated immature secretory granules, and noncoated mature secretory granules. The C-terminal glucagon immunoreactivity was low in all these compartments except in the noncoated mature secretory granules. By contrast, N-terminal glucagon and glicentin immunoreactivities were high at the condensing granule stage and, respectively, increased (N-terminal) or decreased (glicentin) until the mature secretory granule stage. These data suggest that: 1) glucagon precursors and glucagon coexist at different concentrations in secretory compartments of the A-cell; 2) the condensing granules in Golgi cisternae and immature granules consist predominantly of glucagon precursors; and 3) the removal of the peptide masking the C-terminal of the glucagon molecule occurs between the coated and the mature granule stages.
