A morphometric study of age-dependent changes in mitochondrial population of mouse liver and heart.

Mitochondria in sections of liver and heart (wall of left ventricle) from C57BL/6J mice, 8, 30 and 43 to 44 mo. old, were analyzed, using sterological techniques. The mitochondrial volume density decreased with age in both tissues: in liver the value estimated as 43 to 44 mo. of age was 65% the value estimated at 8 mo. of age; in the heart the 43 to 44 mo. value was 84% of the 8-mo. value. In both tissues, the decrease in mitochondrial volume density was the result of a decrease in the mitochondrial numerical density; the average volume of the mitochondrion remained constant throughout life.