Stimulation with heavy metals is known to induce calcium (Ca
2+) mobilization in many cell types. Interference with the measurement of intracellular Ca
2+ concentration by the heavy metals in cells loaded with Ca
2+ indicator fura-2 is an ongoing problem. In this study, we analyzed the effect of heavy metals on the fura-2 fluorescence ratio in human SH-SY5Y neuroblastoma cells by using TPEN, a specific cell-permeable heavy metal chelator. Manganese chloride (30–300
µM) did not cause significant changes in the fura-2 fluorescence ratio. A high concentration (300
µM) of lead acetate induced a slight elevation in the fura-2 fluorescence ratio. In contrast, stimulation with cadmium chloride, mercury chloride or MeHg (3–30
µM) elicited an apparent elevation of the fura-2 fluorescence ratio in a dose-dependent manner. In cells stimulated with 10 or 30
µM cadmium chloride, the addition of TPEN decreased the elevated fura-2 fluorescence ratio to basal levels. In cells stimulated with mercury or MeHg, the addition of TPEN significantly decreased the elevation of the fura-2 fluorescence ratio induced by lower concentrations (10
µM) of mercury or MeHg, but not by higher concentrations (30
µM). Pretreatment with Ca
2+ channel blockers, such as verapamil, 2-APB or lanthanum chloride, resulted in different effects on the fura-2 fluorescence ratio. Our study provides a characterization of the effects of several heavy metals on the mobilization of divalent cations and the toxicity of heavy metals to neuronal cells.
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