A critical period in lifespan of male rats coincides with increased oxidative stress

The oxidative stress theory of aging has provided the best possible explanation for the processes which accompany aging and has received much support, however, in the last few years there have been questions regarding the validity of this theory. We have conducted experiments to determine an array of oxidative stress parameters in blood of male rats at various intervals (1, 4, 8, 12, 18 and 24 months) during their entire lifespan. Established protocols were used to measure plasma antioxidant capacity, erythrocyte plasma membrane redox system (PMRS), lipid and protein oxidation in erythrocytes and plasma, and erythrocyte glutathione (GSH). Our results on the total plasma antioxidant potential, PMRS in erythrocytes, protein and lipid peroxidation, and intracellular reduced GSH provide evidence that oxidative stress is minimal till approximately one-third of the total lifespan (8 months) and there is a spurt in oxidative stress between 8 and 12 months. The identification of a period (corresponding to 8-12 months) in the lifespan of rats coinciding with an spurt in oxidative stress is an interesting finding. No such report is available in humans or in any other model systems during aging.