Antioxidant capacity decreases during growth but not aging in rat serum and brain

The objective of this study was to evaluate the effects of growth and aging on the antioxidant capacities of rat serum and brain, by using two different reactive oxygen species (ROS) generators and two different methods of expressing the results. The antioxidant capacity was determined by using the oxygen radical absorbance capacity (ORAL) assay. The protein content of serum increased significantly during the growth period of day 1 to 6 months of age. The protein content in brain (cortex and cerebellum) extract also tended to increase with the growth. The antioxidant capacity of serum decreased during growth, if the ORAC values were expressed on the basis of serum protein concentration. The antioxidant capacity in brain cortex and cerebellum declined significantly during growth, regardless of which ROS generator was used in the ORAC assay or how the results were expressed (units/ml or units/mg protein). Therefore, the rat pups had higher antioxidant capacity than the adult and old rats. The low plasma antioxidant capacity reported in premature neonates may simply result from a low protein concentration of the plasma, which occurs in neonates. No aging effect was observed on the antioxidant capacity of serum and brain in the adult and old rats.