Dogliotti E, Vitelli A, Terlizzese M, Di Muccio A, Calcagnile A, Saffiotti U, Bignami M
Carcinogenesis. 1987 Jan;8(1):25-31. doi: 10.1093/carcin/8.1.25.
Ouabain resistance (ouar) and 6-thioguanine resistance (6-TGr) mutation frequencies were measured in Chinese hamster ovary cells after treatment with N-ethyl-N-nitrosourea (ENU) for varying periods of time. Maximal mutation frequency at the Na+/K+ ATPase gene locus (ouar mutations) was attained within 5 min of exposure, whereas the mutation frequency at the hypoxanthine guanine phosphoribosyltransferase locus (6-TGr mutations) continued to increase up to 60 min, following the theoretical curve for exponential decay of ENU with time. Detection of DNA single strand breaks (ssb) by alkaline elution showed that maximal levels were attained within 5 min of treatment with ENU. Fast repair of DNA ssb occurred early after exposure (greater than 50% repair within 10 min). Analysis of DNA ethylation products by h.p.l.c. showed initially rapid removal of O2-ethylcytosine (25% in the first hour), slow removal of 7-ethylguanine, 3-ethyladenine and 3-ethylguanine and no removal at all of O6-ethylguanine, O4-ethylthymine and ethylphosphotriesters. These time-course studies reveal different target gene responses in the fixation of DNA damage into mutations.
在用N-乙基-N-亚硝基脲（ENU）处理不同时间后，测定了中国仓鼠卵巢细胞中的哇巴因抗性（ouar）和6-硫鸟嘌呤抗性（6-TGr）突变频率。在暴露5分钟内达到了Na+/K+ ATP酶基因位点（ouar突变）的最大突变频率，而次黄嘌呤鸟嘌呤磷酸核糖转移酶位点（6-TGr突变）的突变频率在60分钟内持续增加，遵循ENU随时间指数衰减的理论曲线。通过碱性洗脱检测DNA单链断裂（ssb）表明，在用ENU处理5分钟内达到了最大水平。DNA单链断裂在暴露后早期快速修复（10分钟内修复超过50%）。通过高效液相色谱法分析DNA乙基化产物表明，最初O2-乙基胞嘧啶快速去除（第一小时内去除25%），7-乙基鸟嘌呤、3-乙基腺嘌呤和3-乙基鸟嘌呤去除缓慢，而O6-乙基鸟嘌呤、O4-乙基胸腺嘧啶和乙基磷酸三酯完全没有去除。这些时间进程研究揭示了在将DNA损伤固定为突变过程中不同的靶基因反应。
