Lowered rates of protein synthesis by mitochondria isolated from organisms of increasing age

The rate of protein synthesis was measured in isolated mitochondria from Drosophila melanogaster and from the livers and kidneys of C57BL/6J mice of increasing ages. Over the life-span of the organisms, the synthesis of mitochondrial proteins decreased to a level which was less than half the original rate. Concomitant with this decrease, the amount of mitochondria which could be isolated from the organisms declined by about 30%. Thus, the separate translational system of mitochondria exhibited an age-related decrease in activity which was in addition to the decrease already observed in the cytoplasmic ribosomal system.