Molecular basis of age-dependent changes in the activity of adenine nucleotide translocase.

(1) Rat-heart mitochondria from 30-month-old animals are 40% less active in translocating adenine nucleotides across the inner membrane than 3-month-old rats. (2) The number of sites available for binding the specific ligands to the adenine nucleotide carrier remains unchanged during aging. (3) The endogenous pool of the adenine nucleotides exhibits an age-dependent fall by more than 25%, essentially at the expense of ATP. The amount of ATP + ADP representing the exchangeable pool for adenine nucleotide translocation is decreased to the same extent. (4) Negatively charged phospholipids as well as polyunsaturated fatty acids of membrane lipids were found to be reduced with aging. (5) The results are discussed in terms of changes in the phospholipid-protein interactions due to the observed alterations in the physical state of the bulk phase of membrane lipids.