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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.

Environmental mercury and mercury compound contamination has increased dramatically since the industrial revolution. This paper describes the toxic effects of mercury on a culture of hybridoma TA7 cells, which produce antibodies against the A-subunit of viskumin. Cells were cultivated on 96-well flat-bottomed plates with RPMI-1640 medium supplemented with 10% fetal calf serum at 37°C in 5% CO2/95% air. The cells were exposed to 0.1nM/l–10μM/l Hg2(NO3)2.2H2O (mercury nitrate) during the exponential growth phase. Toxicity was assessed by using the colorimetric MTT (tetrazolium) assay after exposure for 48 hours. Cell growth and cell survival were evaluated by using percentage indices of cellular content in exposed cells when compared to non-exposed control cells. The concentrations of the no-effect level, the lowest observed effect level and the the highest toxic effect level were registered. The toxic effects of the mercury compound on the hybridoma cells occurred between 0.1μM/l and 10μM/l.

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