Comet assay evaluation of DNA single- and double-strand breaks induction and repair in C3H10T1/2 cells.
Ionizing radiation is a potent inducer of DNA damage because it causes single- and double-strand breaks, alkali-labile sites, base damage, and crosslinks. The interest in ionizing radiation is due to its environmental and clinical implications. Single-strand breaks, which are the initial damage induced by a genotoxic agent, can be used as a biomarker of exposure, whereas the more biologically relevant double-strand breaks can be analyzed to quantify the extent of damage. In the present study the effects of 137CS gamma-radiation at doses of 1, 5, and 10 Gray on DNA and subsequent repair by C3H10T1/2 cells (mouse embryo fibroblasts) were investigated. Two versions of the comet assay, a sensitive method for evaluating DNA damage, were implemented: the alkaline one to detect single-strand breaks, and the neutral one to identify double-strand breaks. The results show a good linear relation between DNA damage and radiation dose, for both single-strand and double-strand breaks. A statistically significant difference with respect to controls was found at the lowest dose of 1 Gy. Heterogeneity in DNA damage within the cell population was observed as a function of radiation dose. Repair kinetics showed that most of the damage was repaired within 2 h after irradiation, and that the highest rejoining rate occurred with the highest dose (10 Gy). Single-strand breaks were completely repaired 24 h after irradiation, whereas residual double-strand breaks were still present. This finding needs further investigation.
Calini
V
V
Dipartimento di Scienze dell'Ambiente e del Territorio, Università degli Studi di Milano-Bicocca, Milan, Italy.
Urani
C
C
Camatini
M
M
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D020552:Comet Assay; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D007700:Kinetics; D051379:Mice
D004277:DNA, Single-Stranded; D004247:DNA