G2 repair and evaluation of the cytogenetic damage induced by low doses of X-irradiation during G0 in human lymphocytes
Pincheira, J.V.; Lopez, I.H.; Tapia, G.O.; Navarrete, M.H.; Oyarzun, C.C.
Biological Research 28(4): 267-275
1995
ISSN/ISBN: 0716-9760 PMID: 9251757 Document Number: 441617
In the present study two cytogenetic parameters were used to evaluate the DNA damage induced by low doses (1 up to 40 rad) of X-ray irradiation in G-0 human lymphocytes. These parameters were the frequency of chromosomal lesions in G-2 and the length of this cell cycle phase. The frequency of chromosomal lesions in G-2 was determined by scoring the number of chromosomal aberrations in G-0 irradiated lymphocytes post treated with two inhibitors of G-2 repair mechanisms : caffeine and 3-aminobenzamide. A dose-dependent increase in chromosomal aberrations yield was detected in G-0 lymphocytes X-ray irradiated with or without post treatment with these two DNA repair inhibitors during G-2. Nevertheless, the dose response in this latter condition was higher than the one detected in control cells, indicating that the increase of irradiation dose in G-0 lymphocytes produces an increment in the number of DNA lesions arriving to be repaired in G-2. The analysis of the dose-response relationships for G-2 length showed an statistically significant X-ray dose-dependent increase (G-2 delay) from 2,5 up to 40 rad and a positive correlation between G-2 delay and the frequency of chromosomal lesions in G-2. These results suggest that the DNA lesions induced by low doses of X-irradiation in G-0 lymphocytes may be higher than that detected by the standard method (control conditions) and may be responsible for an increase in G-2 length. We propose, therefore, that an analysis of these two cytogenetic parameters can improve the evaluation of the DNA damage induced by low doses of X-rays irradiation in G-0 cells.