Genetic effects of low dose radiation: DNA damage and micronucleus in X-rays treated cells

PONZZINIBIO M V; CRUDELI C; PERAL GARCIA P; SEOANE A I

ACTA RADIOLOGICA

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2010 vol. 51 p. 1028 - 1033

0284-1851

Background: Exposure to environmental, diagnostic and occupational sources of radiation frequently involves low doses. Although these doses have no immediately noticeable impact on human health there is great interest in their long-term biological effects. Purpose: The purpose of the present study was to assess immediate and time-delayed DNA damage in two cell lines exposed to low doses of X-rays by using comet assay and micronucleus test, and to compare these two techniques in the analysis of low-dose induced genotoxicity. Material and Methods: CHO and MRC-5 cells were exposed to 50 miliSievert of X-rays and assayed immediately after irradiation and at 16 or 12 passages post-irradiation respectively. Comet assay and micronucleus test were employed. Results: The comet assay values observed in 50 mSv-treated cells were significantly higher than in the control group at both sample times and cell lines (p<0.001). Micronuclei frequencies were higher in treated cells than in the control group (p<0.01, CHO cells passage 16; p<0.05, MRC-5 cells immediately after exposure; p<0.01 MRC-5 cells passage 12). Correlation analysis between the two techniques was statistically significant (Correlation Coefficient: 0.82, p<0.05 and Correlation Coefficient: 0.86, p<0.05 for CHO and MRC-5 cells respectively). Cells scored at passages 12 or 16 showed more damage than those scored immediately after exposure in both cell lines (no statistically significant differences).  Conclusion: Cytomolecular and cytogenetic damage was observed in cells exposed to very low doses of X-rays and their progeny. A single low dose of X-rays was sufficient to induce such response indicating that mammalian cells are exquisitely sensitive to it. Comet and micronucleus assays are sensitive enough to assess this damage even though the former seems to be more efficient.