Pro- and antioxidant activity of chromium(III), iron(III), molybdenum(III) or nickel(II) and their mixtures. 
The aim of this study was to examine the effect of chromium(III), iron(III), molybdenum(III) and nickel(II) and their combinations on pro- and antioxidant activity in mouse embryo fibroblasts and liver cancer cells.  The present study shows that chromium(III), iron(III), nickel(II) and molybdenum(III) induce oxidative stress.  In the case of chromium(III), nickel(II) and molybdenum(III) the intracellular ROS were dominant.  However, in the case of iron(III) MDA was dominant - the end product of lipid peroxidation.  Antioxidant activity of superoxide dismutase and catalase increased in low concentration of chromium(III); however, they decreased in higher concentrations.  The same enzymes decreased after iron(III), nickel(II) and molybdenum(III) treatment in dose dependent manner.  The activity of glutathione peroxidise decreased in dose dependent manner in all used microelements.  Additions of Cr(III) at 200 μM plus Fe(III) at 1000 μM showed synergistic effect in ROS production and in lowering antioxidant activity.  The same type of interaction in pairs Cr(III) at 1000 μM plus Fe(III) or Ni(II) or Mo(III) at concentration of 200 μM was observed.  The protective effects of Cr(III) in antioxidant activity and in lowering intracellular ROS production in pairs of Cr(III) at 200 μM and Ni(II) or Mo(III) at concentration of 1000 μM were observed.