Ultrastructure of the Canine Exocrine Pancreas Following Continuous Intravenous Infusion of Secretin and Injection of Pancreozymin

Electron microscopic studies were performed on exocrine pancreas biopsy specimens from eight dogs, following continuous infusion of secretin and injection of pancreozymin. The excreting process of the proteins by acinar cells is increased after the injection of pancreozymin: there is an enlargement of the acinar lumina, a multiplication of the apical vacuoles, an apical localization and usually a marked depletion of the zymogen granules within the cells. On the other hand, the dense content of the cisternae of the endoplasmic reticulum, the enlargement of the Golgi complex, the abundance of presumed immature zymogen granules are the witnesses of an excreting process which seems to be followed by a rise in the rate of the protein synthesis. The abundance of lysosomal structures chiefly after the pancreozymin injection, can be attributed to an increase of the protein synthesis or to the toxic effects of the drugs. In the washing out period, the emptiness of the acinar lumen can be explained by the diminution of the protein secretion. The main result of this experiment is to show that a presumed specific surstimulation is capable of evoking ultra-structural alterations of the acinar cells which are similar to those observed after experimental intoxication and under pathological conditions.