Cytotoxicity of Cadmium,Selenium,Zinc and Copper to Mouse Myeloma Sp2/0 Cells as Measured by the MTT Assay

Abstract

As part of our general programme to test the toxicity in vitro of heavy metals and, in particular, the interactive cytotoxicity of combinations of these metals, the MTT (tetrazolium) assay was used to test the cytotoxicities of cadmium [Cd(O₂CCH₃)₂], selenium (Na₂SeO₃), zinc (ZnSO₄) and copper (CuSO₄) with an established mouse myeloma cell line (Sp2/0). The influence on the cytotoxicity of cadmium of added subtoxic concentrations of the other three metals was also studied. The IC50 values (50% inhibitory concentrations) to the Sp2/0 cells were as follows: Cd — 10μM, Se — 1μM, Zn — 10μM and Cu — 100μM. When selenium, zinc and copper at high, subtoxic concentrations (10nM, 1μM and 1μM, respectively) were each combined with clearly toxic concentrations of cadmium (10μM and 100μM), the cytotoxicity increase was significant for the cadmium-zinc combination. Previous studies showed that cadmium-zinc combinations at low concentration (5 × 10^–9M) had a synergistic stimulatory effect on cell proliferation in vitro. The present study showed that a toxic concentration of cadmium (0.1mM) and a sub-toxic concentration of zinc (1μM) have a synergistic cytotoxic effect in vitro.