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The intracellular activation of trypsinogen in pancreatic acinar cells is an early and probably initiating event in the development of acute pancreatitis (a frequent and life-threatening inflammatory disease). Endocytic vacuoles are the site of trypsinogen activation in pancreatic acinar cells (Sherwood et al 2007). All inducers of acute pancreatitis trigger prolonged Ca2+ responses, involving release of Ca2+ from intracellular stores and induction of store-operated Ca2+ entry (SOCE). The formation of endocytic vacuoles is a Ca2+ dependent process. The current study examined the specific role of SOCE in the formation of endocytic vacuoles. Fluorescence microscopy and Ca2+ sensitive probes (fluo-4 and fura-2) were utilised to test the response of murine pancreatic acinar cells to supramaximal doses of the secretagogue cholecystokinin (CCK), thapsigargin and the bile acid taurolithocholic acid 3 sulphate (TLCS). All three compounds (known to deplete intracellular Ca2+ stores) induced sustained increase in cytosolic Ca2+ concentration and endocytic vacuole formation. We observed that pharmacological inhibition of SOCE (verified using fura-2 measurements) resulted in significant (more than 40%) inhibition of endocytic vacuole formation. Inhibition of vacuole formation was observed in experiments utilising supramaximal doses of CCK, TLC-S and thapsigargin, suggesting that SOCE plays an important role in vacuole formation in all three of these models of cellular Ca2+ toxicity. It is therefore likely that SOCE is an important component of Ca2+ toxicity, responsible for pancreatic acinar cell damage in the early stages of acute pancreatitis, and is a potentially useful pharmacological target in the development of treatment against this disease. [ABSTRACT FROM AUTHOR]