Reducing equivalents in the aging process.

Abstract

Reducing equivalents may play a major role in the aging process. These metabolites are responsible for the endogenous redox potential in the living cell which is kept under tight regulation. Among their various roles is the ability to donate electrons to reactive oxygen species and by doing so to scavenge them. Most of the reducing equivalents in the cell are molecules with low molecular weights, such as glutathione and NADH which are synthesized by the cell. Other members of this group, such as uric acid are produced as waste products, while others, such as ascorbic acid and tocopherol, are derived from the diet. We studied the role of these equivalents in the aging process in various rat tissues. We demonstrated that the reducing power of a tissue may reflect its antioxidant activity. We used cyclic voltammeter methodology in order to evaluate the overall reducing power of tissue homogenates and other biological fluids. It was found that reducing power changes during the aging process in a bell-shaped manner in liver, lungs and kidneys, but not in heart and brain. We also showed that skin possesses strong reducing power which decreases dramatically with age. A non-invasive procedure to evaluate the oxidation status and the antioxidant activity of skin was developed. Using this method we demonstrated that there is an accumulation of organic peroxide in old skin compared to young skin, supporting the free radical hypothesis of aging.