Yang L L, Maher V M, McCormick J J
Mutat Res. 1982 Jun;94(2):435-47. doi: 10.1016/0027-5107(82)90306-2.
The cytotoxic and mutagenic effect of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti BPDE) in normally excising diploid human cells treated just prior to onset of S was compared with that of cells allowed approximately 16 h for excision repair before onset of S and with that observed in excision-deficient xeroderma pigmentosum (XP12BE) cells. The cells were synchronized by release from density inhibition of cell replication. DNA synthesis began approximately 22 h after the cells were plated at lower density (i.e., 1.4 x 10(4) cells/cm2). The frequency of thioguanine-resistant mutants induced in normal cells treated just prior to onset of S was approximately 12- to 16-fold higher than that observed in cells treated in early G1 or treated in G0 (confluence) and then plated at lower density. The frequency approximated that expected for XP12BE cells from extrapolation of data obtained at lower doses. The frequency of mutants measured in normal cells treated in exponential growth was also much higher than that in the cells treated in early G1 or in G0. No such difference could be seen in XP12BE cells treated in exponential growth or in G0. In contrast to the mutagenicity data in the normal cells, there was no significant difference in the slope of the survival curve of normal cells treated at various times prior to S phase at low densities. However, normal cells treated even at the onset of S exhibited survival equal to XP12BE cells given a 4- to 5-fold lower dose. The data support the hypothesis that DNA synthesis is the cellular event which converts unexcised DNA lesions into mutations. However, they indicate that S is not the event primarily responsible for translating DNA damage into cell death. Accompanying studies on the rate of excision of anti BPDE adducts from the normal cells during the period prior to S support the conclusions.
将在S期开始前刚处理过的正常切除二倍体人类细胞中，（±）-7β，8α-二羟基-9α，10α-环氧-7,8,9,10-四氢苯并[a]芘（反式BPDE）的细胞毒性和诱变作用，与在S期开始前允许大约16小时进行切除修复的细胞以及在切除缺陷的着色性干皮病（XP12BE）细胞中观察到的作用进行了比较。细胞通过从细胞复制的密度抑制中释放来同步化。在以较低密度（即1.4×10⁴个细胞/cm²）接种细胞后约22小时开始DNA合成。在S期开始前刚处理过的正常细胞中诱导产生的硫代鸟嘌呤抗性突变体频率，比在G1期早期处理或在G0期（汇合期）处理然后以较低密度接种的细胞中观察到的频率高约12至16倍。该频率近似于从较低剂量获得的数据外推得出的XP12BE细胞的预期频率。在指数生长期处理的正常细胞中测得的突变体频率也比在G1期早期或G0期处理的细胞中高得多，但在指数生长期或G0期处理的XP12BE细胞中未见这种差异。与正常细胞中的诱变数据相反，在低密度下于S期之前不同时间处理的正常细胞的存活曲线斜率没有显著差异。然而，即使在S期开始时处理的正常细胞，其存活率也与给予低4至5倍剂量的XP12BE细胞相同。这些数据支持了DNA合成是将未切除的DNA损伤转化为突变的细胞事件这一假设。然而，它们表明S期不是将DNA损伤转化为细胞死亡的主要事件。伴随的关于S期之前正常细胞中反式BPDE加合物切除率的研究支持了这些结论。
