Expression and activity of GPx and MnSOD in the liver at different survival time points (3, 20, 26 and 29 months old) in the longevity curve. A) and C) show the expression of GPx and MnSOD studied by real time RT-PCR. Values were normalized to those observed in the samples obtained from the three-month-old group, which was assigned a value of 100%. B) and D) show GPx and MnSOD activity. Values are shown as mean ± SD. (*) indicates P <0.05, (**) indicates P <0.01. Continuous lines show statistically significant differences between the wheel-running animals. Discontinuous lines show statistically significant differences between the sedentary animals. GPx, glutathione peroxidase; MnSOD, manganese superoxide dismutase.