The effect of age on mitochondrial ultrastructure and enzymes.

The ultrastructure of perfused livers and of mitochondrial fractions from 6 months and 30 month-old C57/BL mice were studied. In old mice the liver cell mitochondria were enlarged and rounded with a light "foamy", vacuolated matrix, short cristae and a loss of dense granules. Quantitative studies showed a 60% increase in the mean size and an increased proportion of larger mitochondria in intact 30 month-old perfused livers. Endothelial and Kupffer cell mitochondria were smaller than those of the parenchymal cells. Mitochondria in pellets prepared from 6 and 30 month-old livers were rounded and condensed although there were a few larger and "foamy" mitochondria in the preparations from old mice. Up to 47% of large mitochondria in the old livers were lost during cell fractionation. The levels of cytochrome oxidase and malate dehydrogenase were slightly decreased with age but their cytochemical localization was unchanged.