Influences of Age and Dietary Restriction on Gastrocnemius Electron Transport System Activities in Mice

Alterations in the mitochondrial electron transport system (ETS) may contribute to aging. Dietary restriction (DR) provides a model to investigate retarded aging. ETS activities were measured in gastrocnemius from 10- and 20-month-old B6C3F1female mice fed eitherad libitum(AL) or DR diets (40% < AL). Older (26 month old) AL mice were studied for complex IV. Activities of complexes I, III, and IV decreased 54–74% from 10 to 20 months of age in AL mice. At 10 months, activities of complexes I, III, and IV were 33–64% lower in DR compared to AL mice. TheKmfor ubiquinol-2 of complex III increased 29% by 20 months of age in AL mice while no change occurred in DR mice. TheVmaxof complex IV declined by 90% from 10 to 26 months of age in AL mice and this change was opposed by DR. Complex IV contains high- and low-affinity binding sites. TheKmfor high-affinity sites was not influenced by age or diet through 20 months; however, theKmwas approximately twofold higher at 26 months in AL mice. The percentage of total binding sites which were of high affinity fell from 68% at 10 months in AL mice to 46% at 20 months and was even lower (33%) at 26 months. This value was 80% for DR mice at 10 and 20 months. These alterations with aging in mitochondrial ETS capacities may contribute to decreases in skeletal muscle function.