Publications by authors named "I H Waschulewski"

Okadaic acid, a serine/threonine phosphatase inhibitor, has been shown to inhibit rat pancreatic enzyme secretion by interference with late processes in stimulus-secretion coupling. To further characterize its action, we studied the effect of okadaic acid on secretion of newly synthesized proteins, protein synthesis, and cellular ultrastructure in pancreatic lobules derived from rats stimulated in vivo by feeding the synthetic proteinase inhibitor FOY-305. Okadaic acid completely blocked protein secretion at concentrations that inhibit the Ca2+/calmodulin-dependent protein phosphatase 2b, calcineurin.

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Background: Protein phosphorylation and dephosphorylation events are considered to be key steps in the control of agonist-induced pancreatic enzyme release. This study was designed to characterize the role of serine/threonine phosphatases in phosphoinositol/calcium- and cyclic adenosine monophosphate (cAMP)-mediated stimulus-secretion coupling in rat pancreatic acini.

Methods: Isolated rat pancreatic acini were incubated with either the serine/threonine phosphatase inhibitors okadaic acid, calyculin A, and cyclosporin A or the calmodulin antagonist W-7.

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The effects of the serine/threonine phosphatase inhibitors calyculin A, okadaic acid and the calmodulin antagonist W-7 on amylase secretion were studied in pancreatic acini. Calyculin A and okadaic acid dose-dependently inhibited amylase secretion to basal levels when stimulated with the intracellularly acting secretagogues thapsigargin, 8-br-cAMP or PMA. W-7 dose-dependently inhibited thapsigargin- or 8-br-cAMP-induced amylase secretion.

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The role of serine/threonine phosphatases in Ca2+/IP3- and cAMP- mediated stimulus-secretion coupling was investigated in isolated pancreatic acinar cells. Cyclosporine A, an inhibitor of type 2b serine/threonine phosphatases, maximally reduced CCK-8-stimulated amylase secretion by 33%. In contrast, the secretory response to secretin or PACAP-(1-27) was not significantly altered by cyclosporine A independent of the secretagogue-concentration okadaic acid significantly reduced amylase release, induced by Ca2+/IP3-mediated- (CCK-8) or cAMP-mediated agonists (secretin, PACAP-(1-27), VIP) at concentrations that primarily inactivate type 1 and 2b phosphatases.

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The present study was performed to characterize a direct influence of cyclosporine A (CsA) on exocrine pancreatic enzyme secretion. CsA inhibited dose-dependently amylase release from isolated rat pancreatic acini in response to carbachol or cholecystokinin octapeptide (CCK-8). A significant reduction in amylase release by 17% was observed at 0.

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