Iijima K, Morimoto K
Mutat Res. 1986 Aug;162(1):121-9. doi: 10.1016/0027-5107(86)90077-1.
The induction of sister-chromatid exchanges (SCEs) was studied in phytohemagglutinin (PHA)-stimulated human lymphocytes exposed for 1 h to mitomycin C (MMC, 3 X 10(-6) M), ethyl methanesulphonate (EMS, 2 X 10(-2) M), or 4-nitroquinoline-1-oxide (4NQO, 3 X 10(-5) M) at various cell-cycle stages of 72-h cultures. The doses of the chemical were chosen to give about 20 SCEs per cell when treated at Go. The SCE frequency increased almost linearly with MMC or EMS treatments at later times after PHA stimulation, peaking with those at 36 h (at around the first G1/S boundary in the 2 consecutive cell cycles, which was revealed by concomitant experiments), and then decreased with subsequent treatment times. Cell-cycle kinetics and the cell stages at which the cells were treated were measured by autoradiography and sister-chromatid differential staining. The data show that MMC and EMS produce larger numbers of SCEs when treated at stages closer to the beginning of S, and that the most efficient time of treatment is the G1/S boundary in the first cell cycle of the two consecutive cycles before sampling. Pulse treatment with EMS caused about 3 times larger inductions of SCEs when done at late G1/early S(G1/S boundary) in the first cell cycle compared to that at G0/early G1, whereas identical exposure to MMC at the first G1/S boundary produced only 1.5 times larger numbers of SCEs than that at G0/early G1. EMS and MMC both, however, induced 30-40% larger numbers of SCEs when treated at the G1/S boundary in the first cell cycle than when treated at the second cell cycle before sampling. On the contrary, treatment with 4NQO led to the induction of about the same numbers of SCEs even when treated at different cell-cycle stages before the second G1/S boundary. The SCE frequency in 4NQO-treated cells then decreased with subsequent treatment times.
研究了在72小时培养的不同细胞周期阶段，用植物血凝素（PHA）刺激的人淋巴细胞暴露于丝裂霉素C（MMC，3×10⁻⁶ M）、甲基磺酸乙酯（EMS，2×10⁻² M）或4-硝基喹啉-1-氧化物（4NQO，3×10⁻⁵ M）1小时后姐妹染色单体交换（SCEs）的诱导情况。选择化学物质的剂量，使其在G₀期处理时每个细胞产生约20个SCEs。在PHA刺激后的后期，SCE频率随MMC或EMS处理几乎呈线性增加，在36小时时达到峰值（在连续两个细胞周期的第一个G₁/S边界附近，这通过同步实验揭示），然后随着后续处理时间而下降。通过放射自显影和姐妹染色单体差异染色测量细胞周期动力学和细胞处理时的细胞阶段。数据表明，MMC和EMS在更接近S期开始的阶段处理时产生更多的SCEs，并且最有效的处理时间是采样前连续两个周期中第一个细胞周期的G₁/S边界。与在G₀/早期G₁期相比，在第一个细胞周期的晚期G₁/早期S（G₁/S边界）进行EMS脉冲处理时，SCEs的诱导量大约大三倍，而在第一个G₁/S边界进行相同的MMC暴露时，产生的SCEs数量仅比在G₀/早期G₁期大1.5倍。然而，在采样前，EMS和MMC在第一个细胞周期的G₁/S边界处理时诱导的SCEs数量均比在第二个细胞周期处理时多30 - 40%。相反，即使在第二个G₁/S边界之前的不同细胞周期阶段进行处理，4NQO处理导致的SCEs诱导数量大致相同。4NQO处理细胞中的SCE频率随后随着后续处理时间而下降。
