title: Frequency of spontaneous and induced micronuclei in the peripheral blood of aging mice.
abstract: The mouse peripheral blood micronucleus assay, a measure of DNA damage in erythroblastic cells, was used to determine: (1) the incidence of spontaneously occurring micronucleated reticulocytes (MNRETs) as a function of age, and (2) the induction of micronuclei following treatment of young and old animals with mitomycin C. Male C57BL/6 mice, 92 weeks of age, exhibited a significantly higher frequency of spontaneously occurring peripheral blood MNRETs than mice that were 6 or 10 weeks of age. Mice that were 5-6 weeks or 91-92 weeks old were treated with one dose, or two consecutive doses of mitomycin C; this resulted in dose-related increases in the frequency of MNRETs. Mitomycin C, at a single dose of 1 or 2 mg/kg, induced one-third as many MNRETs in the older animals as compared to the younger animals. When treated with a split dose of mitomycin C (total dose 0.5 to 2 mg/kg), older animals displayed on average two-thirds the mutagenic response of the younger animals. However, analysis of variance performed on these data indicated that the age of the animals did not have a significant effect on their mutagenic response to mitomycin C at any dose level. It appears that aging mice may not be more sensitive to the mutagenic effects of chemically-induced DNA damage than younger mice, suggesting that the higher spontaneous mutation frequency in older mice could be the result of an increased load of accumulated DNA damage.
authors.affiliation: Division of Genetic Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Dass
authors.forename: S F
authors.initials: SF
authors.lastname: Ali
authors.forename: R H
authors.initials: RH
authors.lastname: Heflich
authors.forename: D A
authors.initials: DA
authors.lastname: Casciano
mesh_terms: D000375:Aging / Q000235:genetics*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects / Q000235:genetics*; D015162:Micronucleus Tests; D016685:Mitomycin / Q000633:toxicity; D009153:Mutagens / Q000633:toxicity; D009154:Mutation; D012156:Reticulocytes / Q000648:ultrastructure*
chemical_list: D009153:Mutagens; D016685:Mitomycin