Immunofluorescence and electron-microscopic observations of intermediate cells in the pancreas of mice, rats and humans

The immunohistochemical method supplemented with a transmission electron-microscopic survey was used to investigate the pancreas of mice, rats and humans to demonstrate intermediate cells. Indirect immunofluorescence was applied to paraffin sections of pancreatic samples of normal rats and autopsied humans to localize amylase in the islets and excretory duct cells. The amylase immunofluorescent spots were occasionally detected in the apices and perinuclear cytoplasm of few islet and excretory duct cells, which completely disappeared in the specificity control sections. These cells, respectively, represented the islet amylase and duct amylase intermediate cells. The ultrastructural survey was conducted on pancreatic tissue samples from normal and streptozotocin-diabetic mice and rats to prove the existence of these intermediate cells. Three morphologically distinct types of intermediate cells were recognized and characterized into beta -acinar, alpha -acinar and duct acinar types. The beta -acinar and alpha -acinar cells contained numerous secretory granules with few large and dense, membrane-bound zymogen granules. No clear difference in the frequency of these cells between normal and diabetic tissues was qualitatively observed in either mice or rats. The duct acinar cells were occasionally seen in few small intercalated ducts of the normal mouse pancreas, which contained few dense, membrane-bound zymogen granules adjacent to a prominent Golgi complex. On the other hand, no delta -acinar, pancreatic polypeptide (PP)-acinar or acinoislet cells were observed in both normal and diabetic animals. In conclusion, the present study provides immunohistochemical and morphological evidence on the existence of different types of intermediate cells in the normal and streptozotocin-diabetic pancreas of mice, rats and humans. Although no prevalence of these cells in the streptozotocin-diabetic pancreas was observed qualitatively, their existence throws light on the possible transformation between structurally and functionally different pancreatic cells when subjected to pathological trauma. This concept might be of great significance in beta -cell regeneration in insulin-dependent diabetes mellitus. Copyright (C) 2002 S. Karger AG, Basel.