Grillo Claudia A, Dulout Fernando N, Guerci Alba M
CIGEBA (Centro de Investigaciones en Genetica Basica y Aplicada), National University of La Plata, La Plata, Argentina.
Int J Radiat Biol. 2009 Feb;85(2):159-66. doi: 10.1080/09553000902740143.
The present study was designed to evaluate the effects of sequential exposures to low doses of gamma-radiation that induce a radioadaptive response to a later high-dose of radiation in CHO-K1 cells.
Cells were cultured in four dilution cycles and grown to confluency. Radiation treatment was performed once per cycle with 0.1 Gy gamma-rays. After the last radiation period (chronic radiation) the culture was irradiated with a higher dose (1 Gy). Each cell culture was immediately divided into two fractions: one of them was used to carry out the comet assay and the other for the structural chromosome aberration test. In the first fraction, genotoxic damage was evaluated by degree of damage in 300 cells per experimental point. The second assay was performed with 400 cells per treatment. The statistical analysis was carried out using the chi(2)-test.
Results from these assays demonstrated a genotoxic effect for both the adaptive and acute treatments (p < 0.001). The comet assay showed a significant increase in damage for the combined treatment when compared with 1 Gy treatment (p < 0.001). The frequency of chromosomal aberrations (CA) was lower for the combined treatment than for that using the highest radiation dose.
These results suggest the possible induction of a radioadaptive response after the sequential exposure to very low doses of radiation. The finding of decreased cytogenetic damage after one cell cycle and not immediately after radiation could indicate the eventual potentiation of repair mechanisms.
本研究旨在评估对CHO-K1细胞进行低剂量γ射线连续照射所产生的影响，这种照射会诱导细胞对后续高剂量辐射产生放射适应性反应。
细胞经四个稀释周期培养至汇合状态。每个周期用0.1 Gy的γ射线进行一次辐射处理。在最后一个辐射期（慢性辐射）后，用更高剂量（1 Gy）对培养物进行照射。每种细胞培养物立即分为两部分：一部分用于进行彗星试验，另一部分用于结构染色体畸变试验。在第一部分中，通过每个实验点300个细胞的损伤程度评估遗传毒性损伤。第二个试验每个处理用400个细胞进行。采用卡方检验进行统计分析。
这些试验结果表明适应性处理和急性处理均有遗传毒性作用（p < 0.001）。彗星试验显示，与1 Gy处理相比，联合处理的损伤显著增加（p < 0.001）。联合处理的染色体畸变（CA）频率低于使用最高辐射剂量处理的频率。
这些结果表明，在连续暴露于极低剂量辐射后可能诱导产生放射适应性反应。在一个细胞周期后而非辐射后立即发现细胞遗传损伤减少，这可能表明修复机制最终得到了增强。
