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HORMONES AND SIGNALING
Departments of 1Pediatrics and 2Internal Medicine, Yale University School of Medicine and Veterans Affairs Connecticut Health Care, New Haven, Connecticut
Submitted 26 October 2006 ; accepted in final form 22 February 2007
Aberrant cytosolic Ca2+ flux in pancreatic acinar cells is critical to the pathological pancreatic zymogen activation observed in acute pancreatitis, but the downstream effectors are not known. In this study, we examined the role of Ca2+-activated protein phosphatase 2B (or calcineurin) in zymogen activation. Isolated pancreatic acinar cells were stimulated with supraphysiological caerulein (100 nM) with or without the calcineurin inhibitors FK506 or cell-permeable calcineurin inhibitory peptide (CiP). Chymotrypsin activity was measured as a marker of zymogen activation, and the percent amylase secretion was used as a measure of enzyme secretion. Cytosolic Ca2+ changes were recorded in acinar cells loaded with the intermediate Ca2+-affinity dye fluo-5F using a scanning confocal microscope. A 50% reduction in chymotrypsin activity was observed after pretreatment with 1 µM FK506 or 10 µM CiP. These pretreatments did not affect amylase secretion or the rise in cytosolic Ca2+ after caerulein stimulation. These findings suggest that calcineurin mediates caerulein-induced intra-acinar zymogen activation but not enzyme secretion or the initial caerulein-induced cytosolic Ca2+ signal.
pancreatitis; protein phosphatase 2B; pancreatic acinar; calcium signaling
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