Age-related changes in the lipofuscin accumulation of brain and heart.

Lipofuscin is the end-product of intracellular lipid peroxidation and the accumulation results from the cellular metabolism during aging (life stage). We suggested that the accumulation of cardiac lipofuscin was dependent on the specific metabolic rate of mammals. Slower rate of cardiac lipofuscin accumulation (against absolute lifespan) was observed in the animals of larger body size. The rate of cardiac lipofuscin accumulation was correlated with the specific metabolic rate, and inversely correlated with the brain weight of mammals. The first appearance of lipofuscin granules was 8 weeks of age in the hippocampus and in the thalamus. In the case of cerebral cortex (laminae III), lipofuscin granules were first found at 3-month-old rats. The rate of lipofuscin accumulation was the highest in the hippocampus (y = 0.286x - 0.099, r = 0.963) among the three regions examined. In the case of cerebral cortex and thalamus, the slower rate of lipofuscin accumulation was observed (y = 0.072x - 0.14, r = 0.797 for cerebral cortex; y = 0.067X - 0.14, r = 0.953 for thalamus). It is noticed that the most abundant accumulation and the highest rate of lipofuscin accumulation are the hippocampus. Even the hippocampus, the rate and the magnitude of lipofuscin accumulation was low as compared with cardiac muscles. From these results, it is suggested that brains have better protective system against oxidative stress than other organs do.