| Previous studies have demonstrated an age--related decline in resistance to oxidative stress and that these effects of aging could be at least partially prevented with physical activity. Acute exercise results in a transient increase in reactive oxygen species, which at low concentrations are important for cell signaling and up--regulation of endogenous antioxidant enzymes. This study tested the hypothesis that acute exercise increases protection against a subsequent oxidative challenge, and that this protective effect is attenuated with age. We compared young (20 +/- 1y, n=8) and older (58 +/- 6y, n=9) healthy men and women. Resistance to oxidative stress was measured by the F2-isoprostane response to forearm ischemia/reperfusion (I/R) trial. Each participant underwent the I/R trial twice, in random order; once after performing 45--min of cycling at 60% of maximal oxygen consumption on the preceding day (IRX) and a control trial without any physical activity for 2 days prior (IRC). Baseline F2-isoprostane levels were significantly lower at the IRX trial compared to IRC (P<0.05) and not different between groups. F2--isoprostane response to IRX was significantly lower compared to IRC in young (P<0.05) but not different in the older group. Superoxide Dismutase activity in response to acute exercise was significantly higher in young compared to older adults (P<0.05). These data suggest that the signal transduction of acute exercise is impaired with aging, resulting in decreased translation of acute exercise into protection against I/R injury. |
