[Free radicals and aging].

The aging process is an universal phenomenon. All individuals of a given species are dead by some age characteristic of the species. In spite of many biological and clinical observations on the changes that occur during aging, understanding about the causes of aging or the mechanisms determining "the life span potential" is till now dissatisfying, due to a plenty of theories: programmed aging (Hayflick), error catastrophe theory (Orgel) and free radical theory (Harman) are the most widely to be discussed, with a growing tendance to blend one into the other. The free radical theory of aging is basically found on three main observations: free radicals (FR) are extremely reactive species; oxy free radicals production, mainly superoxide anions O2-., is a constant phenomenon in our organism, with beneficial (defense against microbial aggression by phagocytes) but also highly damaging effects at the molecular and cellular levels; natural defense or control mechanisms occur, both enzymatic (superoxide dismutase--SOD--, catalase, glutathione peroxidase) or chemical ("antioxidants" such as vitamin E, vitamin C, glutathion). In the free radical theory of aging, some inbalance between production and control mechanisms is supposed to result in the continuous or progressive production and accumulation of deleterious changes throughout the cells and tissues, generating intense functional disorder at each level of organization (ultra structures, cells, organs). This could be the causality of "normal aging", but not the only one.(ABSTRACT TRUNCATED AT 250 WORDS)