Morphometrical and immunocytochemical characterization of peri-insular and tele-insular acinar cells in the rat pancreas.

Morphometrical and immunocytochemical techniques have been applied in order to characterize the pancreatic acinar cells located in peri-insular and tele-insular regions of the pancreas. The results obtained, have shown that the acinar cells of the peri-insular regions are twice as large as those of the tele-insular. On the other hand, the volume density of all organelles, except that of the zymogen granules, remains constant implying that the larger the cell, the larger are its organelles. For the zymogen granules however, their volume density was found to be higher in peri-insular acinar cells. The immunofluorescence technique applied for the demonstration of amylase and chymotrypsinogen has confirmed the presence of an inhomogeneity in the staining. Acinar cells in peri-insular regions show a brighter fluorescent staining. At the electron microscope level, both amylase and chymotrypsinogen were demonstrated in all organelles of acinar cells involved in protein secretion. Quantitative evaluations demonstrate no major differences in the intensity of labeling per micron2 between organelles of peri-insular and tele-insular cells. These results put together demonstrate that peri-insular acinar cells contain higher amounts of secretory proteins because their organelles are larger and their zymogen granules are more numerous. The partition of the exocrine pancreas into peri- and tele-insular regions, confirmed herein through morphometrical and cytochemical techniques, is discussed in relation to the possible influence of the endocrine secretion arising from the islets of Langerhans on the surrounding acinar cells.