Schwartz J L
Chromosoma. 1986;93(5):409-12. doi: 10.1007/BF00285822.
Culture of cells in high exogenous levels (greater than 10(-4) M) of bromodeoxyuridine (BrdUrd) or thymidine will increase the baseline sister chromatid exchange (SCE) frequency. The effect is thought to be related to the balance of the DNA precursors thymidine and deoxycytidine. Exogenous addition of deoxycytidine will reverse this effect. Single and twin SCEs were analysed in Colcemid-induced tetraploid Chinese hamster ovary cells exposed to different concentrations of BrdUrd to determine at what stage SCEs are induced by high levels of BrdUrd. In cells exposed to low concentrations of BrdUrd (10(-5) M), equal numbers of SCEs were induced in each of the two cell cycles. With increasing concentrations of BrdUrd (10(-4) to 2 X 10(-4) M), SCE frequency increased in both cell cycles, but far more SCEs were induced in the second cell cycle. Deoxycytidine (2 X 10(-4) M) reduced the frequency of SCEs primarily by reducing the frequency of SCEs induced in the second cell cycle. Treatment with 3-aminobenzamide (3AB), a potent inhibitor of poly(ADP-ribose) polymerase, produced effects similar to exposure to high levels of BrdUrd including inducing SCEs in the second replication cycle. This suggests a similar mechanism of action. Deoxycytidine had no effect on 3AB-induced SCEs, however, and there was no interaction between 3AB and high exogenous levels of BrdUrd in SCE induction. Thus these two agents probably act through different mechanisms.
在高外源性水平（大于10⁻⁴ M）的溴脱氧尿苷（BrdUrd）或胸腺嘧啶核苷中培养细胞，会增加基线姐妹染色单体交换（SCE）频率。这种效应被认为与DNA前体胸腺嘧啶核苷和脱氧胞苷的平衡有关。外源性添加脱氧胞苷会逆转这种效应。在暴露于不同浓度BrdUrd的秋水仙酰胺诱导的四倍体中国仓鼠卵巢细胞中分析单SCE和双SCE，以确定高水平BrdUrd在哪个阶段诱导SCE。在暴露于低浓度BrdUrd（10⁻⁵ M）的细胞中，两个细胞周期中诱导的SCE数量相等。随着BrdUrd浓度增加（10⁻⁴至2×10⁻⁴ M），两个细胞周期中的SCE频率均增加，但第二个细胞周期中诱导的SCE要多得多。脱氧胞苷（2×10⁻⁴ M）主要通过降低第二个细胞周期中诱导的SCE频率来降低SCE频率。用聚（ADP - 核糖）聚合酶的有效抑制剂3 - 氨基苯甲酰胺（3AB）处理，产生的效应类似于暴露于高水平BrdUrd，包括在第二个复制周期中诱导SCE。这表明作用机制相似。然而，脱氧胞苷对3AB诱导的SCE没有影响，并且在SCE诱导中3AB与高外源性水平的BrdUrd之间没有相互作用。因此，这两种药物可能通过不同机制起作用。
