VMP1 expression correlates with acinar cell cytoplasmic vacuolization in arginine-induced acute pancreatitis

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Abstract
Recently, we described the cloning of VMP1 (vacuole membrane protein 1). In vitro expression of VMP1 promotes formation of cytoplasmic vacuoles followed by cell death. In order to test if VMP1 expression is related to the cytoplasmic vacuolization of the acinar cells during acute pancreatitis, we studied the in vivo expression of the new gene during arginine-induced acute pancreatitis. Male Wistar rats injected with 500 mg/100 g of L-arginine were time-course sacrificed and pancreas tissue removed. Northern blot analysis showed maximal induction of VMP1 after 24 h remaining high after 48 h of arginine administration. Significant increase in the number of TUNEL-stained cells were found at those periods. After 24 and 48 h of arginine administration, light micrographs from thin plastic toluidine blue sections revealed numerous vacuoles in the cytoplasm of acinar cells. In situ hybridization studies showed high expression of VMP1 in acinar cells with cytoplasmic vacuolization. VMP1 mRNA highly and significantly correlated with vacuole formation. These results suggest that VMP1 expression may be involved in the cytoplasmic vacuolization of acinar cells during the early stage of acute pancreatitis.