Hydrogen peroxide inhibits Ca(2+) efflux through plasma membrane Ca(2+)-ATPase in mouse parotid acinar cells

Intracellular Ca(2+) mobilization is closely linked with the initiation of salivary secretion in parotid acinar cells. Reactive oxygen species (ROS) are known to be related to a variety of oxidative stress-induced cellular disorders and believed to be involved in salivary impairments. In this study, we investigated the underlying mechanism of hydrogen peroxide (H(2)O(2)) on cytosolic Ca(2+) accumulation in mouse parotid acinar cells. Intracellular Ca(2+) levels were slowly elevated when 1 mM H(2)O(2) was perfused in the presence of normal extracellular Ca(2+). In a Ca(2+)-free medium, 1 mM H(2)O(2) still enhanced the intracellular Ca(2+) level. Ca(2+) entry tested using manganese quenching technique was not affected by perfusion of 1 mM H(2)O(2). On the other hand, 10 mM H(2)O(2) induced more rapid Ca(2+) accumulation and facilitated Ca(2+) entry from extracellular fluid. Ca(2+) refill into intracellular Ca(2+) store and inositol 1,4,5-trisphosphate (1 µM)-induced Ca(2+) release from Ca(2+) store was not affected by 1 mM H(2)O(2) in permeabilized cells. Ca(2+) efflux through plasma membrane Ca(2+)-ATPase (PMCA) was markedly blocked by 1 mM H(2)O(2) in thapsigargin-treated intact acinar cells. Antioxidants, either catalase or dithiothreitol, completely protected H(2)O(2)-induced Ca(2+) accumulation through PMCA inactivation. From the above results, we suggest that excessive production of H(2)O(2) under pathological conditions may lead to cytosolic Ca(2+) accumulation and that the primary mechanism of H(2)O(2)-induced Ca(2+) accumulation is likely to inhibit Ca(2+) efflux through PMCA rather than mobilize Ca(2+) ions from extracellular medium or intracellular stores in mouse parotid acinar cells.