Myhr B C, Dipaolo J A
Chem Biol Interact. 1978 Apr;21(1):1-18. doi: 10.1016/0009-2797(78)90064-9.
8-Azaguanine (AZG)- and 6-thioguanine (TG)-resistant cells (mutants) were induced in Chinese hamster V79-4 cells by 0.1--2.5 microgram/ml N-acetoxy-2-acetyle aminofluorine (AcAAF) treatments in the presence of 5% fetal bovine serum (FBS). The frequency of resistant colonies increased from 1 to 47 per 10(5) survivors. The effect of caffeine (50--200 microgram/ml) during the mutagenesis expression period was determined by adding caffeine 1--24 h after AcAAF. The medium was replaced after 48 h exposures so that caffeine was absent during subsequent selection with AZG or TG. No significant change in the AcAAF-induced mutant frequency occurred with any treatment combination although caffeine greatly enhanced the lethality associated with AcAAF treatments. Thus, caffeine interferes with postreplication repair in V79-4 cells without affecting the probability of error of the repair process. These results were obtained with a quantitative mutagenesis assay in which the cells were reseeded prior to selection to achieve maximum expression without interference from metabolic crossfeeding. In contrast, the commonly used in situ assay is subject to serious interference from crossfeeding and yields an artifactual enhancement of AcAAF mutagenesis by caffeine.
在5%胎牛血清（FBS）存在的情况下，用0.1 - 2.5微克/毫升的N - 乙酰氧基 - 2 - 乙酰氨基芴（AcAAF）处理中国仓鼠V79 - 4细胞，诱导出对8 - 氮杂鸟嘌呤（AZG）和6 - 硫代鸟嘌呤（TG）具有抗性的细胞（突变体）。抗性集落的频率从每10⁵个存活细胞中的1个增加到47个。在诱变表达期加入咖啡因（50 - 200微克/毫升），即在AcAAF处理后1 - 24小时加入咖啡因，以确定其效果。暴露48小时后更换培养基，以便在随后用AZG或TG进行选择时不存在咖啡因。尽管咖啡因极大地增强了与AcAAF处理相关的致死率，但任何处理组合均未使AcAAF诱导的突变频率发生显著变化。因此，咖啡因干扰V79 - 4细胞中的复制后修复，而不影响修复过程的错误概率。这些结果是通过定量诱变测定获得的，在该测定中，细胞在选择前重新接种，以实现最大表达，而不受代谢交叉喂养的干扰。相比之下，常用的原位测定法受到交叉喂养的严重干扰，并且咖啡因会人为增强AcAAF的诱变作用。
