Secretory apparatus assessed by analysis of pancreatic secretory stress protein expression in a rat model of chronic pancreatitis

Abstract

Secretory stress proteins (SSP) are a family of proteins including isoforms of pancreatitis-associated protein (PAP) and pancreatic stone protein (PSP/reg). In vitro exposure to trypsin results in the formation of insoluble fibrillar structures. SSP are constitutively secreted into pancreatic juice at low levels. The WBN/Kob rat is a model for chronic pancreatitis, displaying focal inflammation, destruction of the parenchyma and changes in the architecture of the acinar cell; the synthesis and secretion of SSP are also increased. We have investigated the secretory apparatus by SSP immunohistochemistry at the light- and electron-microscopical (EM) levels. Immunocytochemistry of PSP/reg in Wistar control rats reveals low levels, with individual acinar cells exhibiting high immunoreactivity in zymogen granules. PAP is not detectable. In the WBN/Kob rat, PSP/reg and PAP immunoreactivity is markedly increased. Double immunofluorescence for PSP/reg and PAP I or II demonstrates that these proteins colocalize to the same cell. Acinar cells change their secretory architecture by fusion of zymogen granules and elongation of the fused organelles. The immunogold technique has demonstrated an increase of SSP in zymogen granules in WBN/Kob rats. PSP/reg-positive zymogen granules fuse to form elongated structures with fibrillar contents. An extensive PSP/reg-positive fibrillar network is established in the cytosol. Extracellular fibrils have been observed in several ductules. Thus, SSP-derived fibrils form concomitantly with acinar damage in the WBN/Kob rat. Based on the known tryptic cleavage site of SSP, the in vivo generation of fibrils is presumably the result of premature trypsin activation.

Regenerating 1 and 3b Gene Expression in the Pancreas of Type 2 Diabetic Goto-Kakizaki (GK) Rats

“…A comparable phenomenon exists around diabetic GK rat islets and associated-ducts, which are in close contact with CD68 + and MHC class II + macrophages, neutrophils immature myeloid cells and cells immunoreactive for reactive oxygen species and lipid peroxidation [2], [3], [31]. A peri-islet REG-1 distribution has also been observed: 1) in Wistar rats (as single cells or groups of cells) [32], but it was very faint in our study; 2) in type 1 nonobese diabetic (NOD) mice and NOD-rat insulin promoter-1-human IFNβ mice [33].…”