Immunocytochemical studies of pancreatic acinar cells in normal and streptozotocin-induced diabetic rats.

Amylase and chymotrypsinogen in pancreatic tissue from normal and diabetic rats were revealed by immunocytochemistry and analyzed biochemically. In acinar cells of control animals, both enzymes were localized with high resolution in the rough endoplasmic reticulum, Golgi apparatus, immature and mature secretory granules. Quantitative evaluations of the intensities of labelings have demonstrated, for both enzymes, the presence of an increasing gradient which followed precisely their secretory pathway. This gradient reflects the normal processing of both proteins through secretion. In streptozotocin-induced diabetic animals, labeling for amylase in acinar cells was markedly reduced (remaining about 11% of the normal values). The gradient along the secretory pathway was abolished, indicating an alteration in the processing and secretion of amylase. On the other hand, labeling for chymotrypsinogen was significantly increased (to 170% p less than 0.0005), and its processing remained normal. In insulin-treated diabetic animals, immunolabeling for amylase was restored and the gradient re-established, indicating a normalization of the secretion. Labeling for chymotrypsinogen was reduced towards normal values. These results were found to be in agreement with those obtained by biochemical approaches and demonstrate that, in the diabetic condition, secretion of amylase is selectively impaired.