Age-related changes in redox status of rat serum.

Aging and age-related diseases are known to be associated with increased oxidative stress. To protect against the deleterious effects of oxidative stress, a well-co-ordinated network of enzymatic and nonenzymatic anti-oxidant defense systems is essential. In the present study, we investigated the age-related redox status of serum by analyzing hydrogen peroxide, hydroxyl radical, superoxide-scavenging abilities, and other redox markers. Results showed the anti-oxidative capacity to be significantly decreased in serum of aged rats, which was accompanied by a marked increase in peroxide levels. Our analyses also revealed that levels of nitrated proteins, induced by peroxynitrite treatment, were higher in old rats than in young rats. Our results clearly indicated that the serum redox balance shifted toward oxidation during aging. To further confirm this age-related redox shift, we quantified the changes in thiol content. The total thiol level was found to be significantly decreased in the aged group. We also noticed an age-related reduction in serum albumin, which may be partially responsible for the decreased serum thiol levels. A similar pattern can be explained by low levels of serum GSH in old rats compared to young rats. The significance of the present study is the data showing increased oxidative stress in serum during aging, attributed to a decrease in major antioxidant components in serum.