Changes in hepatic cell mitochondria during parabiosis between old and young rats.

Electron-micrographic measurement studies have been made on the hepatic cell mitochondria of the long-lived parabiotic unions between old and young rats. The mitochondria of the younger partners were significantly larger in size and those of the older partners were significantly larger in number and smaller in size compared with those of young and old control rats, respectively. The mitochondrial cristae seemed to become more compactly arranged in the younger partners and more sparsely in the older ones. The influence of parabiosis between different aged rats upon age changes in mitochondria and their function is discussed.