Succinic dehydrogenase activity in human muscle mitochondria during aging:a quantitative cytochemical investigation

A quantitative cytochemical study has been carried out on succinic dehydrog enase (SDH) activity in biopsy samples of vastus lateralis (VL) and anterio r tibialis (AT) muscles from healthy men undergoing orthopaedic surgery. Ac cording to their age, the patients were divided into: young (25.0 +/-4.4 ye ars), middle-aged (50.4 +/-7.5 years) and old (75.5 +/-3.9 years) groups. B ioptically excised samples were processed for copper ferrocyanide preferent ial SDH cytochemistry. By a computer-assisted image analyser, we calculated the ratio (R): overall area of the precipitates due to the enzyme activity /area of each mitochondrion. No significant difference was found among the three age groups, despite an 8% increase of R in the adult vs. the other gr oups. R values are related to mitochondrial morphofunctional features since they may be modulated by enzyme activity and the physico-chemical conditio ns of the organelle membranes. Thus, R quantitation enables to estimate the mitochondrial capacities for adenosinetriphosphate provision. In this cont ext, our present findings confirm previous data reporting a substantial age -related stability of muscle mitochondrial enzyme levels. In aging, energy- deficient sarcomeres are supported to be negatively selected and eliminated , while the surviving ones appear to maintain an adequate SDH activity. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.