Kinetic repair of chromosome breaks in normal human liver cells irradiated with γ-rays

Objective: To investigated the 48-hour kinetic repair of G2-phase normal human liver cells (cell line L02) exposed to γ-rays. Methods: The chromosomal breaks were detected by premature chromosome condensation technique. Results: The chromatid-type and isochromatid-type breaks increased with increase of the dose at 0 hour measured by PCC, the number of chromatid-type breaks was several times more than that of isochromatid-type breaks. Through further 24-hour incubation after exposure to radiation, both of these types of breaks were repaired to different extents, i.e., by 50% for chromatid-type breaks, 15% for isochromatid-type ones at most. At 48th hour, there was a slight change of chromosome breaks compared with that of 24th hour (P>0.05). Conclusion: The main type of chromosomal break is chromatid-type after exposure to γ-rays, and these bveaks are easy to be repaired. Though the isochromatid-type break is obviously less than that of the chromatid-type but is difficult to be repaired, indicating that the isochromatid type break is the important factor causing cell death and canceration when cells bave been exposed to γradiation. (authors)