Effects of prolonged ACTH-stimulation on adrenocortical accumulation of lipofuscin granules in aged rats

Subcellular deposition of lipofuscin granules is a marker of aging. Human a nd rodent adrenal cortices accumulate lipofuscin granules with age, but the mechanism that leads to the accumulation is not known. The ultrastructural appearance of lipofuscin granules resembles that of secondary lysosomes. S ince adrenocortical subcellular events are predominantly influenced by ACTH action, we therefore studied the effect of prolonged ACTH-stimulation on a drenocortical accumulation of secondary lysosome-like granules, designated herein as lipofuscin granules. Using aged Fischer 344 male rats as a model, we found that a 7 day ACTH stimulation exerts a reducing effect on adrenoc ortical lipofuscin accumulation. Thus, adrenocortical accumulation of lipof uscin granules with age in vivo may not be an irreversible process. (C) 199 9 Harcourt Publishers Ltd.