Decreased activity of the phosphate carrier and modification of lipids in cardiac mitochondria from senescent rats.

1. A comparative study of the effects of aging on the transport of phosphate and on the lipid composition in cardiac mitochondria isolated from young and aged rats was carried out. 2. Mitochondria from aged rats (26 month old) translocate phosphate much more slowly than do mitochondria from young control rats (4 month old). 3. Kinetic analysis of the phosphate transport show that only the Vmax of this process is decreased while there is no change in the Km value. 4. There is no appreciable difference in either the respiratory control ratios or in the ADP/O ratios between mitochondria from young and aged rats. 5. The heart mitochondrial lipid composition is altered in aged rats; in particular, the cholesterol/phospholipid molar ratio increases and the content of cardiolipin decreases with aging.