A new cytogenetic approach for the evaluation of mutagenic potential of chemicals that induce cell cycle arrest in the G(2) phase.

摘要

The aim of the present study was to develop and standardize a cytogenetic approach for evaluation of the mutagenic potential of chemicals that induce cell cycle arrest in the G(2) phase. Even though cytogenetic end-points such as sister chromatid exchange (SCE) have been extensively used to indirectly assess the DNA-damaging potential of various chemicals, they are based on metaphase chromosome analysis. Cells delayed in G(2) phase after chemical exposure are not included in conventional SCE analysis. The yield of SCEs obtained, therefore, can be biased, since predominantly undamaged cells proceed to metaphase without delay. To overcome this shortcoming of conventional SCE analysis, the use of a new cytogenetic approach for genotoxic studies is presented that enables the analysis of SCEs directly in G(2) phase using drug-induced premature chromosome condensation in cultured peripheral blood lymphocytes. By means of this method, firstly, the possibility that SCE analysis in metaphase chromosomes underestimates the mutagenic potential of various chemicals was tested. Secondly, whether the genotoxic potential of suspected carcinogens could be evaluated using SCE analysis in G(2) phase, even at exposures that arrest cells in G(2) phase, was examined. Thirdly, whether an important part of the background variation in SCE frequency among individuals is due to the delay of affected cells in G(2) phase, rather than to a true biological variation in the cytogenetic end-point used, was tested. The results showed that a higher SCE frequency was scored in G(2) phase than in metaphase. Subsequently, the mutagenic potential of chemicals that temporarily arrest cells in G(2) phase could now be evaluated more accurately. In addition, it may be of interest to further examine the involvement of cell cycle kinetics in the baseline SCE variation among individuals since a lesser SCE variability was observed when the analysis was carried out in G(2) phase rather than at metaphase.