Phenylarsine oxide evokes intracellular calcium increases and amylase secretion in isolated rat pancreatic acinar cells

The effects of the thiol reagent, phenylarsine oxide (PAO, 10(-5)-10(-3) M) , a membrane-permeable trivalent arsenical compound that specifically compl exes vicinal sulfhydryl groups of proteins to form stable-ring structures, were studied by monitoring intracellular free calcium concentration ([Ca2+] (i)) and amylase secretion in collagenase dispersed rat pancreatic acinar c ells. PAO increased [Ca2+](i) by mobilizing calcium from intracellular stor es, since this increase was observed in the absence of extracellular calciu m. PAO also prevented the CCK-8-inducecl signal of [Ca2+](i) and inhibited the oscillatory pattern initiated by aluminium fluoride (AlF4-). In additio n to the effects of PAO on calcium mobilization, it caused a significant in crease in amylase secretion and reduced the secretory response to either CC K-8 or AlF4-. The effects of PAO on both [Ca2+](i) and amylase release were reversed by the sulfhydryl reducing agent, dithiothreitol (2 mM). Pretreat ment of acinar cells with high concentration of ryanodine (50 mu M) reduced the PAO-evoked calcium release. However, PAO was still able to release a s mall fraction of Ca2+ from acinar cells in which agonist-releasable Ca2+ po ols had been previously depleted by thapsigargin (0.5 mu M) and ryanodine r eceptors were blocked by 50 mu M ryanodine. We conclude chat, in pancreatic acinar cells, PAO mainly releases Ca2+ from the ryanodine-sensitive calciu m pool and consequently induces amylase secretion. These effects are likely to be due to the oxidizing effects of this compound. CELL SIGNAL 11;10:727 -734, 1999. (C) 1999 Elsevier Science Inc.