Cadmium affects human health through occupational and environmental exposure. In this report, we present the response of mitochondrial and cytoplasmic antioxidant enzymes of CRL-1439 cells exposed to different concentrations (0-150 microM) of CdCl2 for 24 h at 37 degrees C. Exposure of liver cells to 50 microM CdCl2 increased mitochondrial catalase and glutathione reductase (GR) activities more than the cytoplasmic enzymes. Although the mitochondrial selenium-dependent glutathione peroxidase (Se-GPx) showed less enzymatic activity than the cytoplasmic enzyme, the mitochondrial selenium-independent glutathione peroxidase (non-Se-GPx) showed a slight increase in activity over its cytoplasmic counterpart compared to untreated controls. With 100 microM CdCl2, catalase maintained an increase in specific activity in mitochondria over the cytoplasmic enzyme compared to the controls. The level of GR was higher in the cytoplasm than in the mitochondria. However, the activity of Se-GPx and non-Se-GPx decreased slightly in the mitochondria compared to their cytoplasmic counterparts. Exposure of cells to 150 microM CdCl2 decreased all antioxidant enzyme activities compared to the 100 microM CdCl2-treated samples due to toxic effect. Each antioxidant enzyme exhibited its own pattern of activation or inhibition upon exposure to different concentrations of cadmium, with more oxidative stress observed in the mitochondria.