Comparison of the effects of epidermal chalone in young and aging mice.

The ability of epidermal chalones to produce inhibition of epidermal mitotic and DNA synthetic activities was investigated in young (2 month old) and old (27 month old) mice. Extracts of epidermal chalone were prepared from the skin of mice of these diferent ages, and these extracts were then tested for their inhibitory capacities against the same age group from which they were extracted, and also against the mice of the other age group. It was found that the ability of mouse skin to produce tissue-specific agents with mitotic and DNA-synthetic inhibitory capabilities did not change significantly with increasing age. There were however, decreases in both the labeling and mitotic indices with aging in untreated mice. These data suggest that chalone-type inhibitory mechanisms are not primarily responsible for the increased cell cycle times seen to occur with aging in normal tissues.