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

Intracellular calcium (Ca) 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 (HO) on intracellular Ca accumulation in mouse pancreatic acinar cells. Perfusion of HO at 300 µM resulted in additional elevation of intracellular Ca levels and termination of oscillatory Ca signals induced by carbamylcholine (CCh) in the presence of normal extracellular Ca. Antioxidants, catalase or DTT, completely prevented HO-induced additional Ca increase and termination of Ca oscillation. In Ca-free medium, HO still enhanced CCh-induced intracellular Ca levels and thapsigargin (TG) mimicked HO-induced cytosolic Ca increase. Furthermore, HO-induced elevation of intracellular Ca levels was abolished under sarco/endoplasmic reticulum Ca ATPase-inactivated condition by TG pretreatment with CCh. HO at 300 µM failed to affect store-operated Ca entry or Ca extrusion through plasma membrane. Additionally, ruthenium red, a mitochondrial Ca uniporter blocker, failed to attenuate HO-induced intracellular Ca elevation. These results provide evidence that excessive generation of HO in pathological conditions could accumulate intracellular Ca by attenuating refilling of internal Ca stores rather than by inhibiting Ca extrusion to extracellular fluid or enhancing Ca mobilization from extracellular medium in mouse pancreatic acinar cells.