Capucci M S, Hoffmann M E, De Groot A, Natarajan A T
MGC Department of Radiation Genetics and Chemical Mutagenesis, State University of Leiden, The Netherlands.
Environ Mol Mutagen. 1995;26(1):72-8. doi: 10.1002/em.2850260111.
The cytotoxicity of streptozotocin (STZ) was investigated in Chinese hamster fibroblast lines (CHO-9 and V79) in comparison to two other alkylating agents, methylnitrosourea (MNU) and ethylnitrosourea (ENU), using cell survival as the endpoint. It was found that V79 cells were far more resistant to methylation induced by STZ and MNU than CHO-9 cells (20 and four times, respectively) but equally sensitive to the ethylating agent ENU. The extent of STZ-induced DNA methylation was estimated by analyzing the extent of O6-metG and N7-metG adducts in the DNA of treated cells through high-performance liquid chromatography (HPLC) with electrochemical detection. The number of adducts as well the efficiencies of their removal from the DNA were similar in both cell lines. The response of these cells to the presence of DNA damage was evaluated by analysis of STZ effects on DNA replication and cell cycle progression. Measurement of [3H]-thymidine incorporation showed a similar pattern of response at the level of inhibition of DNA synthesis in both cell lines. However, analysis of metaphase cells 36 hr after STZ exposure showed an accumulation of cells in the second cycle in the CHO-9 line, indicating induction of a cell cycle arrest. Only a slight effect was observed on cell cycle progression in V79 cells, indicating that the methylation resistance of these cells could be related to their ability to progress through the cell cycle despite the presence of DNA lesions.
以细胞存活率为终点，将链脲佐菌素（STZ）与另外两种烷化剂甲基亚硝基脲（MNU）和乙基亚硝基脲（ENU）进行比较，研究其对中国仓鼠成纤维细胞系（CHO-9和V79）的细胞毒性。结果发现，V79细胞对STZ和MNU诱导的甲基化的抗性远高于CHO-9细胞（分别为20倍和4倍），但对乙基化剂ENU的敏感性相同。通过高效液相色谱（HPLC）结合电化学检测分析处理后细胞DNA中O6-甲基鸟嘌呤（O6-metG）和N7-甲基鸟嘌呤（N7-metG）加合物的程度，估计STZ诱导的DNA甲基化程度。两种细胞系中加合物的数量及其从DNA中去除的效率相似。通过分析STZ对DNA复制和细胞周期进程的影响，评估这些细胞对DNA损伤存在的反应。[3H] - 胸腺嘧啶核苷掺入量的测量显示，两种细胞系在DNA合成抑制水平上的反应模式相似。然而，STZ暴露36小时后中期细胞的分析显示，CHO-9细胞系中细胞在第二个周期积累，表明诱导了细胞周期停滞。在V79细胞中仅观察到对细胞周期进程的轻微影响，表明这些细胞的甲基化抗性可能与其在存在DNA损伤的情况下通过细胞周期的能力有关。
