Human skeletal muscle mitochondria in aging: lack of detectable morphological and enzymic defects.

We have investigated structural and functional properties of skeletal muscle mitochondria obtained from biopsies from young and old individuals. The morphometric analysis of muscle sections revealed a tendency to an increase of total area, numerical density and volume density of mitochondria in the aged. The enzymatic activities of NADH-Coenzyme Q reductase, succinate cytochrome c reductase, ubiquinol-cytochrome c reductase exhibited a high variability of specific activities without any correlation with age. Expression of the values as enzyme turnovers reduced the variability but was unable to reveal any age-dependent modification.