Effect of experimental prolongation of life span on lipofuscin content and lysosomal enzyme activity in the brain of the housefly, Musca domestica.

The effect of experimental prolongation of life span on the rate of lipofuscin accumulation in the giant neurons of the brain and lysosomal enzyme activity in the head was studied in the male housefly, Musca domestica. The median and the maximum life span of the flies was extended twofold by varying their flight activity. The rate of lipofuscin accumulation was significantly faster in short-lived, high-activity flies as compared to the long-lived, low-activity flies. The maximal content of lipofuscin in the neurons was similar in both groups but was reached at a much older age in the low-activity flies. Age-associated profiles of the activities of the lysosomal enzymes beta-glycerophosphatase and beta-acetylglucosaminidase did not correspond to the mortality characteristics of the housefly populations. The results support the view that lipofuscin represents an integral aspect of aging and may be used as a cellular marker for physiological age whereas lysosomal enzyme activities do not seem to be directly related to the rate of aging.