Effect of spontaneous exercise on antioxidant capacity in rat muscles determined by electron spin resonance

Aim: The effect of physical activity on antioxidant capacity in muscle remains unknown. This study investigated the effect of spontaneous exercise on antioxidant capacity in rat muscles determined by electron spin resonance (ESR), which is a technique for the direct detection of free radicals. Methods: Ten-week-old male Wistar rats were housed individually in cages with a running wheel. Rats were classified as high activity (HA), middle activity (MA) or low activity group (LA), based on an assessment of running distance covered over a 23-week period. After 23 weeks of housing, soleus (Sol), plantaris (Pl), gastrocnemius [deep/surface portions (GasD/GasS)] and heart (Hrt) muscles were isolated, and scavenging activity against superoxide anions (O-2(-)) and hydroxyl radicals (HO.) was determined by ESR using a spin-trap chemical. The citrate synthase (CS) activity was used as a marker of mitochondrial oxidative phosphorylation capacity. Results: Among the parameters measured, only O-2(-) scavenging activity in GasD significantly correlated with the running distance. The highest O-2(-) scavenging activity was observed in Hrt of HA rats. The O-2(-) scavenging activity in Pl of MA rats was significantly higher than that of LA rats. The O-2(-) scavenging activity of Sol and GasS was not significantly different between the three groups. Furthermore, the HO. scavenging activity of any muscle specimens was similar among the three groups and did not correlate with running distance at all. CS activity did not significantly differ between the three groups. Conclusion: These data suggest that O-2(-) scavenging activity in specific types of muscle tissues would increase especially in spontaneously active animals. However, HO. scavenging activity would not.