Aim: 

Nickel (Ni) is a genotoxic carcinogen but the mechanism of its effect is not well understood. Ni can increase or decrease proliferation depending on cell type and concentration, modifying DNA polimerase activity. In the present study we analyze the effect of culture conditions on hepatocyte proliferation and cell viability after Ni treatment.

Methods: 

Isolated rat hepatocytes (10⁶ cells) were cultured in RPMI 1640 medium for 24 hours and treated with different NiCl₂ concentrations for different times. DNA synthesis was determined by the incorporation of ³H thymidine. Ni content was measured with ICP-AES. Cell viability was assayed with XTT method.

Results: 

A 24 h Ni treatment caused a dose dependent decrease of DNA synthesis and cell viability with 80% inhibition at 1 mM Ni. Only 40% inhibition of thymidine uptake in soluble fraction was observed. The effect was present also after 48 h restoring without Ni. The determination of Ni content showed that hepatocytes can transport and accumulate this metal. The absence of dexamethasone and serum in the culture medium increased drastically the inibitory effect of Ni at 0.5 mM and 1 mM while at lower concentrations was ineffective.When cells were cultured at lower cell density (0.5 10⁶ cells) Ni caused a complete inhibition of DNA synthesis.

Conclusion: 

In rat hepatocytes Ni decreases DNA synthesis and cell viability. The effect on proliferation seems dependent on cell kind, as an increased cell proliferation is reported in keratinocytes. Moreover the data show that Ni effects are dependent on cell culture conditions and in particular that dexamethasone, serum and high cell density are protective agaist elevated Ni concentrations. The reported results suggest that care should be taken to choose conditions which are relevant for in vitro analysis of Ni effects.