RESEARCH ARTICLE Potential Interactions of Calcium-Sensitive Reagents with Zinc Ion in Different Cultured

Background Several chemicals have been widely used to evaluate the involvement of free Ca2+ in mech-anisms underlying a variety of biological responses for decades. Here, we report high reac-tivity to zinc of well-known Ca2+-sensitive reagents in diverse cultured cells. Methodology/Principal Findings In rat astrocytic C6 glioma cells loaded with the fluorescent Ca2+ dye Fluo-3, the addition of ZnCl2 gradually increased the fluorescence intensity in a manner sensitive to the Ca 2+ che-lator EGTA irrespective of added CaCl2. The addition of the Ca 2+ ionophore A23187 drasti-cally increased Fluo-3 fluorescence in the absence of ZnCl2, while the addition of the Zn 2+ ionophore pyrithione rapidly and additionally increased the fluorescence in the presence of ZnCl2, but not in its absence. In cells loaded with the zinc dye FluoZin-3 along with Fluo-3,