The age-related accumulation of protein carbonyl in rat liver correlates with the age-related decline in liver proteolytic activities

Increases of protein carbonyl in animal tissues have been associated with t he aging process. So far, the accumulation of oxidized proteins, highly sus ceptible to proteolysis, has been attributed to age-related changes in prot easomal alkaline proteases. Carbonyl in protein was monitored in sir differ ent tissues of male Sprague-Dawley rats fed ad libitum up to the age of 27 months, and of 24- and 27-month-old rats subjected to anti-aging diet restr iction (every-other-day feeding ad libitum). Alkaline protease activities a nd liver lysosomal proteolysis were studied. The levels of protein carbonyl were significantly different in different tissues, and quite stable throug hout life; accumulation was restricted to liver tissue very late in life, b etween ages 24 and 27 months; was fully prevented by diet restriction; was not accompanied by any diet-restriction-sensitive decline of alkaline prote ase activity; and was accompanied by a dramatic age-related decline in lyso somal proteolysis that was partially prevented by anti-aging diet restricti on. No correlation was found between levels of alkaline protease activity a nd levels of protein carbonyl in the different tissues from younger animals . It is concluded that the process of autophagy, a well-known mechanism for cell maintenance, may deserve more interest in aging studies.