Immunocytochemical and Biochemical Evaluation of Pancreatic Lipase in Acinar Cells of Control and Streptozotocin-Induced Diabetic Rats

Pancreatic lipase was revealed by immunocytochemistry and analyzed biochemically in pancreatic tissue from control, diabetic, and insulin-treated diabetic rats. In the three groups of animals, lipase antigenic sites were detected with high resolution in the acinar cells in the compartments involved in protein secretion: rough endoplasmic reticulum, Golgi apparatus, and secretory zymogen granules. The quantitative evaluation of the intensities of labeling has demonstrated that, in contrast to other pancreatic proteins, lipase is concentrated only at the transition between the Golgi apparatus and the condensing vacuoles. This indicates that, although sharing the same secretory pathway as amylase and chymotrypsinogen, lipase may in fact be processed differently. On the other hand, when compared with controls, lipase immunolabelings in tissues with diabetic condition were higher in all the cellular compartments. Treatment of diabetic animals with insulin was found to restore these levels to those obtained in control condition. The biochemical determination of lipase activities in pancreatic tissues confirmed the immunocytochemical data. These results, together with those obtained previously for amylase and chymotrypsinogen, indicate that in diabetic condition secretion from the acinar cells is significantly altered, which may influence intestinal digestion and absorption processes. These modifications, and the enhancement of lipase in particular, could play a role in the pathogenesis of the hyperlipidemic condition present in diabetes.