Estudios in vitro de exposición crónica a dosis bajas de radiación ionizante

DULOUT, FERNANDO; SEOANE, ANALÍA; GRILLO, CLAUDIA; GÜERCI, ALBA

¨Buenos Aires

Taller; Taller regional para la introducción de la norma ISO 19238 y su implementación en los laboratorios de dosimetría biológica latinoamericanos; 2006

Autoridad Regulatoria Nuclear, Comisión Nacional de Energia Atómica

Purpose: Genomic instability involves time delayed events and can be manifested as elevated rates of heritable changes in the progeny of irradiated cells. To study the induction of chromosomal instability by very low doses of radiation Chinese Hamster Ovary (CHO) cells were exposed to 10 – 50 milisieverts (mSv) (_10 – 50 miligrays (mGy)) of x-rays. Materials and methods: Control and irradiated cell populations were assayed for citogenetic analysis (chromosomal aberrations, micronucleus and anaphase-telophase), comet assay and ﻻ-H2AX foci formation at the first cell division post-irradiation and at every four passages thereafter up to 16 passages post-irradiation. Results: Frequencies of micronuclei, anaphase-telophase alterations and chromosomal aberrations were increased when the cells were analysed immediately after x-ray exposure. Micronuclei and anaphase-telophase alterations showed significantly increased frequencies when they were analysed at 12 and 16 population doublings after exposure to 50 mSv. Chromosomal aberrations increased significantly at 12 and 16 population doublings after exposure to 10 mSv and 50 mSv. DNA damage was observed immediately after exposition and at all experimental points in a dose-dependent and statistically significant manner. Nevertheless, cells scored at passages 4 and 8 showed less DNA damage than those observed at 0 or 12 passages. In addition, damage was higher (but not significantly) in cells analyzed at passage 12th than those observed immediately after exposition. A strong correlation between comet assay and ﻻ-H2AX analysis was observed in our results. Conclusions: Our results are consistent with the presence of a phenomenon by which the initial DNA damage in the surviving cells is memorized. Micronuclei and achromatic lessions were the main cytogenetic damage observed in cells exposed to very low doses of x-rays, indicating that these low doses are able to induce genetic instability. Both comet assay and ﻻ-H2AX focus analysis were considered useful techniques to detect DNA damage and our results let suggest that they are also sensitive to study time delayed events like occurs in genomic instability.