Frequency of spontaneous chromosome aberrations in mice: effects of age

In this paper, we present data on chromosome aberration frequencies in mice which served as unexposed controls in a variety of radiation and chemical toxicology experiments conducted in our laboratory in recent years. All chr omosome aberration data were obtained by chromosome painting. In peripheral blood lymphocytes from 102 animals, the frequencies of translocations and insertions increased significantly with age. No increase with age was seen for dicentrics or acentric fragments, When the data were analyzed by strain , the age-related increase in translocation frequencies was observed only i n the 71 homozygous C57BL/6 mice and not in any of the three heterozygous s trains. Very few aberrations of any type were observed in 62 bone marrow sa mples, and no effect of age was seen for any aberration type in this tissue . These results are similar to those observed in unexposed humans, and sugg est that the increase in translocations is not the result of accumulated da mage from chronic 'background' environmental exposures but instead may be d ue to biological processes associated with aging. (C) 1999 Elsevier Science B.V. All rights reserved.