Effect of dephostatin on intracellular free calcium concentration and amylase secretion in isolated rat pancreatic acinar cells

This study investigates the effects of dephostatin, a new tyrosine phosphat ase inhibitor, on intracellular free calcium concentration ([Ca2+](i)) and amylase secretion in collagenase dispersed rat pancreatic acinar cells. Dep hostatin evoked a sustained elevation in [Ca2+](i) by mobilizing calcium fr om intracellular calcium stores in either the absence of extracellular calc ium or the presence of lanthanium chloride (LaCl3). Pretreatment of acinar cells with dephostatin prevented cholecystokinin-octapeptide (CCK-8)-induce d signal of [Ca2+](i) and inhibited the oscillatory pattern initiated by al uminium fluoride (AlF4-), whereas co-incubation with CCK-8 enhances the pla teau phase of calcium response to CCK-8 without modifying the transient cal cium spike. The effects of dephostatin on calcium mobilization were reverse d by the presence of the sulfhydryl reducing agent, dithiothreitol. Stimula tion of acinar cells with thapsigargin in the absence of extracellular Ca2 resulted in a transient rise in [Ca2+](i). Application of dephostatin in t he continuous presence of thapsigargin caused a small but sustained elevati on in [Ca-+(2)](i). These results suggest that dephostatin can mobilize Ca2 + from both a thapsigargin-sensitive and thapsigargin-insensitive intracell ular stores in pancreatic acinar cells. In addition, dephostatin can stimul ate the release of amylase from pancreatic acinar cells and moreover, reduc e the secretory response to CCK-8. The results indicate that dephostatin ca n release calcium from intracellular calcium pools and consequently induces amylase secretion in pancreatic acinar cells. These effects are likely due to the oxidizing effects of this compound.