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The double action of Cd2+ in the types and frequencies of chromosomal aberrations induced in human lymphocytes exposed to gamma rays

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The presence of agents that prevent repair of DNA breaks caused by irradiation can induce more breaks than not. Cadmium is a factor that may cause DNA damage and also inactivate repair enzymes. This paper describes the investigation of chromosomal aberrations induced in human lymphocytes by the combined action of cadmium and gamma rays. Four groups were investigated: Cd alone, gamma radiation alone, Cd/gamma and gamma/Cd. In the combined treatments, there were clear differences in the frequencies of dicentrics and fragments in lymphocytes treated with variable cadmium concentrations with the same dose of gamma rays. Increasing the cadmium concentration at the same radiation dose, the frequency of dicentrics decreased but the frequency of fragments increased. The difference in frequency of chromosomal aberrations was not detected posttreatment at cadmium concentrations of 0.05/μg/ml and 0.10/μg/ml. This means that cadmium does not affect the induction of chromosomal aberrations after repair time. We thus suggest that cadmium does not directly cause chromosomal aberrations but affects the DNA damage-repair ability of lymphocytes. Cadmium can induce increasing fragments and decreasing dicentrics (blocking of cohesive free ends) by binding the blunt free-end of double strand breaks or creating near-site double-strand breaks (nonblunt free end), which leads to difficulty in rejoining the breaks.

Keywords: chromosomal aberrations, chromatid aberrations, cadmium, gamma rays, cohesive free ends, blunt free ends, un-blunt free ends, DNA damage, enzyme repair, human lymphocytes, radiation dose, DNA repair, low radiation

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