QUANTITATIVE STUDIES ON CONCURRENT FACTORS IN NEOPLASTIC TRANSFORMATION

对BALB/3T3克隆A41-1-1细胞株进行了以下研究 检测：细胞毒性、哇巴因抗性(OUA-r)突变、形态 碱性条件下的肿瘤转化、DNA损伤与修复 用高效液相色谱法测定烷基化DNA加合物的洗脱和去除。这个 确定了这些生物终点的相对反应水平 用烷化剂处理后，N-甲基-N‘-硝基-N- 亚硝胺(MNNG)和N-乙基亚硝脲(ENU)。几次解离 去年报道的这一现象得到了证实，并在今年进行了进一步调查 年。暴露在含有给定初始浓度的介质中的时间 ENU浓度决定了显著不同的最大反应 用于不同的端点。短暴露持续时间(5分钟)为 足以诱导最大水平的OUA-r突变和DNA单链 链断裂(SSB)，而转化的最大诱导为 良好的细胞毒性需要45-60分钟。关于的其他研究 用中国人的ENU进行了暴露时间依赖的反应 仓鼠卵巢(CHO)细胞，其OUA-r突变和6-硫鸟嘌呤 可检测耐药(6-TG-r)突变。细菌的诱导动力学 CHO细胞OUA-r突变和SSB表现出早期最大诱导性 与在BALB/3T3细胞中观察到的相似，而6-TG-r突变 在时间上以逐渐较高的速度诱导，与 基于电势衰减的线性关系的理论曲线 Enu在媒介中。BALB/3T3细胞快速去除06-乙基鸟嘌呤 N3-乙基拉丁的去除程度较小，而在60分钟内没有去除 检测出N7-乙基鸟嘌呤、04-乙基胸腺嘧啶和乙基磷酸三酯。 然而，CHO细胞不能修复06-乙基鸟嘌呤 损伤。因此，06-烷基鸟嘌呤的修复不太可能解释 OUA-r突变和SSB的早期最大反应。世俗的 解离模型正在进一步研究，以澄清 转化诱导时间长。

The BALB/3T3 clone A41-1-1 cell line was studied with the following assays: cytotoxicity, ouabain resistance (oua-r) mutations, morphological neoplastic transformation, DNA damage and repair as measured by alkaline elution and removal of alkylated DNA adducts as measured by HPLC. The relative levels of response for these biological end points were determined after treatment with the alkylating agents, N-methyl-N'-nitro-N- nitrosoguanidine (MNNG) and N-ethlnitrosourea (ENU). A few dissociation phenomenon, reported last year, was confirmed and further investigated this year. Duration of the exposure to a medium containing a given initial concentration of ENU determined maximal responses that differed remarkably for different end-points. Short exposure duration times (5 min) were sufficient to induce maximal levels of oua-r mutations and of DNA single strand breaks (ssb), whereas the maximal induction of transformation as well as of cytotoxicity required 45-60 mins. Additional studies of exposure time-dependent responses were conducted with ENU in Chinese hamster ovary (CHO) cells, for which both oua-r mutations and 6-thioguanine resistance (6-TG-r) mutations can be assayed. The induction kenetics of oua-r mutations and ssb in CHO cells showed early maximal induction analogous to that observed in the BALB/3T3 cells, whereas 6-TG-r mutations were induced at progressively higher rates in time, consistent with a theoretical curve based on a linear relationship to expotential decay of ENU in the medium. BALB/3T3 cells removed 06-ethylguanine rapidly and N3-ethyladeine to a lesser degree, whereas no removal within 60 min was detected for N7-ethylguanine, 04-ethylthymine and ethyl-phosphotriesters. The CHO cells, however, were not capable of repairing 06-ethylguanine lesions. Repair of 06-alkylguanine, therefore, is unlikely to explain the early maximal response of oua-r mutations and ssb. The temporal dissociation model is being further studied to clarify the basis for the long induction times for transformation.