NADH-Coenzyme Q reductase was assayed in platelet mitochondrial membranes obtained from 19 pools of two venous blood samples from female young (19–30 years) individuals and 18 pools from aged ones (66–107 years). The enzyme activities were not significantly changed in the two groups, but a decrease of sensitivity to the specific inhibitor, rotenone, occurred in a substantial number of aged individuals. The results are in agreement with the predictions of the mitochondrial theory of ageing and may be used to develop a sensitive biomarker of the ageing process.
