title: Influence of age and sex on the spontaneous DNA damage detected by micronucleus test and comet assay in mice peripheral blood cells.
abstract: We have investigated the normal variations in basal DNA damage detected by Comet assay in leukocytes and micronucleated erythrocytes (MNE) using the Micronucleus test (MN) in peripheral blood cells from 45 female and male mice from different age groups (newborns, 3.5, 12, and 104 weeks) to clarify age and sex-related changes. Comparison of basal DNA damage detected by Comet assay showed significantly increased values in 104 weeks old mice in relation to the other ages (P < or = 0.01), and newborn mice showed higher values in MNE frequency when compared to all the other groups (P < or = 0.01). A positive correlation was observed between Damage Frequency (r =0.382, P = 0.010) and Damage Index (r = 0.640, P < 0.001) and age. Age was also correlated with the ratio of polychromatic erythrocytes/normachromatic erythrocytes (PCE/NCE) (r = -0.473, P = 0.001), and the MNE frequency was positively correlated with the ratio of PCE/NCE (r = 0.454, P = 0.002). These results suggest an age-related slow down of DNA repair efficiency of DNA damage and/or DNA damage accumulation. Furthermore, data on the spontaneous MNE frequency indicate that the reticuloendothelial system matures with age, and there is a close relationship between erythropoiesis and micronucleus induction in erythrocytes. The influence of sex in the parameters analyzed was less clear. In conclusion, age seems to influence in basal DNA damage and should be considered in genotoxicity studies using mice. Finally, comparisons between assays must be made with care when different cells are compared (e.g. leukocytes and erythrocytes), as found with the Comet assay and MN test.
authors.affiliation: Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, CP 15053, CEP 91501-970, Porto Alegre, RS, Brazil.
authors.forename: Vanina Dahlström
authors.initials: VD
authors.lastname: Heuser
authors.forename: Vanessa Moraes
authors.initials: VM
authors.lastname: de Andrade
authors.forename: Alessandra
authors.initials: A
authors.lastname: Peres
authors.forename: Luisa Maria
authors.initials: LM
authors.lastname: Gomes de Macedo Braga
authors.forename: José Arthur
authors.initials: JA
authors.lastname: Bogo Chies
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D020552:Comet Assay / Q000379:methods*; D004249:DNA Damage; D004260:DNA Repair; D004913:Erythrocytes, Abnormal / Q000502:physiology; D005260:Female; D007962:Leukocytes / Q000502:physiology; D008297:Male; D051379:Mice; D015162:Micronucleus Tests / Q000379:methods*; D011247:Pregnancy; D012737:Sex Factors