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 B6C3F(1) female mice fed either ad 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 PO 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, The K-m for ubiquinol-2 of complex III increased 29% by 20 months of age in AL mice while no change occurred in DR mice, The V-max of 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, The K-m for high-affinity sites was not influenced by age or diet through 20 months; however, the K-m was 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. (C) 1996 Academic Press, Inc.