Age-Related Change in the α-Tocopherolquinone/α-Tocopherol Ratio in the Rat Erythrocyte Membrane

Abstract

α-Tocopherol (α-Toc), a lipophilic phenolic antioxidant that is localized mainly in the biomembrane, protects cells against oxidation-associated cytotoxicity by prevention of membrane lipid peroxidation, maintenance of the redox balance intracellular thiols and stabilization of the membrane structure. We investigated the age-related changes in redox dynamics of α-Toc in plasma and erythrocyte membrane of an elderly (66 weeks old) and young group (10 weeks old). Total, α-, β+γ-, δ-Toc and α-tocopherolquinone (α-TocQ) in plasma and erythrocyte membrane were determined by high-performance liquid chromatography (HPLC) with a series of multiple coulometric working electrodes (CWE). Rat venous blood sample was divided into plasma and erythrocyte layers by centrifugation, and then erythrocyte membrane sample was prepared according to the method of Dodge et al. under a stream of nitrogen. In plasma, total and α-Toc concentrations were increased, and β+γ-, δ-Toc and α-TocQ concentrations were decreased age-dependently. In the erythrocyte membrane, total, α-TocQ concentrations and three fractions of tocopherols decreased age-dependently. Also, a decrease in the α-TocQ/α-Toc ratio in erythrocyte membrane was observed in the elderly group. These findings suggest that the α-Toc uptake in erythrocyte membrane and utilization rate of α-Toc in erythrocyte membrane decline age-dependently. This decline may promote membrane lipid peroxidation. α-Toc redox dynamics in erythrocyte membrane were useful to investigate the pathophysiology of aging mechanisms related to oxidative stress.