Insulin and C-peptide co-localization in the beta granules of normal human pancreas and insulinomas. A quantitative immunocytochemical approach.

It has been shown, by using the immunogold technique, that C-peptide and insulin are co-localized in the mature granules of human pancreatic beta cells and insulinomas with typical granules. The mean gold bead densities of both C-peptide and insulin were at least twice as high in the normal pancreas when compared with the insulinomas. The mean granule diameter of the insulinoma cells (D = 0.30 +/- 0.12 micron) was smaller than that of human pancreatic cells (D = 0.45 +/- 0.15 micron). The morphometric data indicate that each of the antigens (C-peptide and insulin) is distributed similarly in the halos and the dense cores of the beta granules. Thus, no topological segregation of these two antigens occurs within the beta granules of either normal human pancreas or insulinomas.