Changes in the distribution of anionic constituents in secretory granules of mouse pancreatic acinar cells after pilocarpine-induced degranulation

We used cationized colloidal gold (CCG) to investigate the distribution of anionic sites in different secretory granules of mouse pancreatic acinar cell regranulation. Localization of anionic sites with CCG was carried out on ultrathin sections of a mouse pancreas, fixed in Karnovsky's fixative and OsO₄ and embedded in Araldite. After pilocarpine-stimulated degranulation, there was a marked diminution in the anionic charge density of immature and mature granules of the 4-hr group (≅43.0 gold particles/μm²) compared to the 8-hr mature granules group (≅64.6 gold particles/μm²). Scattergram analysis to investigate the correlation between section profile size and cationized gold labeling density revealed a reverse correlation, the small granule profiles demonstrated a higher density compared to the larger profiles of the same group. On the basis of these observations, it appears that a post-translational processing of secretory content influences the granule anionic charge and thus may affect the intragranular buffer capacity.