Modifying effect of aging on chemical carcinogenesis. A review

The age-associated elevation in tumor incidence is generally attributed to the age-related accumulation of a total effective dose of carcinogenic agents and/or time of exposure, or is regarded as a consequence of disturbances of the hormono-metabolic pattern and the decline in immunity vigor with increasing age. This review deals with the data available on the peculiarities of realization of the effect of different carcinogenic chemicals in various tissues of young mature and old animals. The results of the analysis of the literature data show that aging may involve either an increase or a decrease in the sensitivity of tissues and the whole organism to the action of carcinogenic chemicals or no changes at all. These differences are due to the specific characteristics of the age-associated dynamics of activity of drug-metabolizing enzymes and the proliferative activity of target tissue controlled by hormonal factors and chalones.