Hydrogen peroxide attenuates refilling of intracellular calcium store in mouse pancreatic acinar cells

Intracellular calcium (Ca(2+)) oscillation is an initial event in digestive enzyme secretion of pancreatic acinar cells. Reactive oxygen species are known to be associated with a variety of oxidative stress-induced cellular disorders including pancreatitis. In this study, we investigated the effect of hydrogen peroxide (H(2)O(2)) on intracellular Ca(2+) accumulation in mouse pancreatic acinar cells. Perfusion of H(2)O(2) at 300 µM resulted in additional elevation of intracellular Ca(2+) levels and termination of oscillatory Ca(2+) signals induced by carbamylcholine (CCh) in the presence of normal extracellular Ca(2+). Antioxidants, catalase or DTT, completely prevented H(2)O(2)-induced additional Ca(2+) increase and termination of Ca(2+) oscillation. In Ca(2+)-free medium, H(2)O(2) still enhanced CCh-induced intracellular Ca(2+) levels and thapsigargin (TG) mimicked H(2)O(2)-induced cytosolic Ca(2+) increase. Furthermore, H(2)O(2)-induced elevation of intracellular Ca(2+) levels was abolished under sarco/endoplasmic reticulum Ca(2+) ATPase-inactivated condition by TG pretreatment with CCh. H(2)O(2) at 300 µM failed to affect store-operated Ca(2+) entry or Ca(2+) extrusion through plasma membrane. Additionally, ruthenium red, a mitochondrial Ca(2+) uniporter blocker, failed to attenuate H(2)O(2)-induced intracellular Ca(2+) elevation. These results provide evidence that excessive generation of H(2)O(2) in pathological conditions could accumulate intracellular Ca(2+) by attenuating refilling of internal Ca(2+) stores rather than by inhibiting Ca(2+) extrusion to extracellular fluid or enhancing Ca(2+) mobilization from extracellular medium in mouse pancreatic acinar cells.