Nowak C
Freie Universität Berlin, Institut für Genetik, Germany.
Mutat Res. 1990 Jun;230(2):255-61. doi: 10.1016/0027-5107(90)90063-a.
Asynchronously growing V79 hamster cells were treated with hypotonic solutions of different osmolalities, with ethyl methanesulfonate (EMS) or a combination of these 2 agents. Four different fixation times (8, 10, 14, 18 h) were tested. Hypotonic treatment alone induced chromosomal aberrations (CA), leading to very high frequencies at low osmolalities (50 mOsm/kg H2O). EMS also induced CA, but a comparison of EMS and hypotonicity revealed that EMS induced fewer aberrations at the maximum doses tested. A combined treatment produced contradictory results, depending on the sampling time: 8 and 14 h led to a clear elevation of EMS-induced CA by hypotonicity, 10- and 18-h sampling times led to a decrease in the aberration frequency in EMS and hypotonically treated cells. The observation that the choice of sampling time significantly influences the incidence of chromosomal aberrations is of particular interest for in vitro assays. In this study the 4 different sampling times are not enough to allow meaningful conclusions about additive or synergistic effects of the mutagens tested. These contradictory results are caused, on the one hand, by the very steep dose-response curve after hypotonic treatment and on the other hand by the varying degree of cell-cycle delay after combination treatment. This makes a valid comparison of the CA frequencies impossible because no 2 sampling times contain the same mixture of cells.
对异步生长的V79仓鼠细胞用不同渗透压的低渗溶液、甲基磺酸乙酯（EMS）或这两种试剂的组合进行处理。测试了4种不同的固定时间（8、10、14、18小时）。单独的低渗处理诱导染色体畸变（CA），在低渗透压（50 mOsm/kg H2O）时导致非常高的频率。EMS也诱导CA，但EMS与低渗处理的比较显示，在测试的最大剂量下，EMS诱导的畸变较少。联合处理产生了矛盾的结果，这取决于取样时间：8小时和14小时导致低渗处理使EMS诱导的CA明显增加，10小时和18小时取样时间导致EMS处理和低渗处理细胞的畸变频率降低。取样时间的选择显著影响染色体畸变发生率这一观察结果对于体外试验尤为重要。在本研究中，4种不同的取样时间不足以就所测试诱变剂的相加或协同效应得出有意义的结论。这些矛盾的结果一方面是由低渗处理后非常陡峭的剂量反应曲线引起的，另一方面是由联合处理后不同程度的细胞周期延迟引起的。这使得无法对CA频率进行有效的比较，因为没有两个取样时间包含相同的细胞混合物。
