Nagasawa H, Keng P, Harley R, Dahlberg W, Little J B
Laboratory of Radiobiology, Harvard School of Public Health, Boston, MA 02115.
Int J Radiat Biol. 1994 Oct;66(4):373-9. doi: 10.1080/09553009414551311.
Seven human and rodent cell lines with markedly differing cellular radiosensitivities were examined by the anti-Br-dUrd antibody and flow cytometric method in order to measure the progression of S phase cells and their accumulation in the G2 phase of the cell cycle after gamma-irradiation. Exponentially growing cells were labelled with 10 microM BrdUrd for 2 h, gamma-irradiated, then washed and cultured at 37 degrees C. At 2-h intervals postirradiation, the cells were harvested and fixed for flow cytometric analysis. Two parameter distributions of BrdUrd content and DNA content were analysed. The time intervals for unirradiated labelled cells to progress from S to G2/M phase were about 450 min for the human squamous cell carcinoma cell lines SCC-12B.2 (D0 = 2.66 Gy), SQ-20B (D0 = 2.39 Gy) and SCC-61 (D0 = 1.07 Gy) as well as for wild-type CHO cells (D0 = 2.62 Gy). After irradiation with 2 Gy, SCC-12B.2, SQ-20B, CHO and human diploid AG1521 cells showed similar small G2/M delays (about 1 h), whereas, a G2/M delay of about 2.2 h occurred in radiosensitive SCC-61 cells and delays of 5.0-7.7 h were observed in two extremely radiosensitive mutant cell strains (human AT homozygote and CHO xrs-5 respectively). When the cells were irradiated with doses yielding similar levels of survival (about 10%), however, the duration of the G2/M delay was generally similar (2-4 h) in all seven cell lines indicating a parallel relationship between radiation-induced G2/M delay and cellular radiosensitivity. These results suggest that the delay time may be related to the level of unrepaired damage present in the cell as it approaches mitosis.
为了测量γ射线照射后S期细胞的进程及其在细胞周期G2期的积累，采用抗BrdUrd抗体和流式细胞术对七种细胞放射敏感性明显不同的人和啮齿动物细胞系进行了检测。对数生长期的细胞用10μM BrdUrd标记2小时，进行γ射线照射，然后洗涤并在37℃下培养。照射后每隔2小时收集细胞并固定，用于流式细胞术分析。分析BrdUrd含量和DNA含量的双参数分布。对于人鳞状细胞癌细胞系SCC-12B.2（D0 = 2.66 Gy）、SQ-20B（D0 = 2.39 Gy）和SCC-61（D0 = 1.07 Gy）以及野生型CHO细胞（D0 = 2.62 Gy），未照射的标记细胞从S期进入G2/M期的时间间隔约为450分钟。用2 Gy照射后，SCC-12B.2、SQ-20B、CHO和人二倍体AG1521细胞表现出相似的较小G2/M期延迟（约1小时），而放射敏感的SCC-61细胞出现约2.2小时的G2/M期延迟，在两种极度放射敏感的突变细胞株（分别为人AT纯合子和CHO xrs-5）中观察到5.0 - 7.7小时的延迟。然而，当用产生相似存活水平（约10%）的剂量照射细胞时，所有七种细胞系中G2/M期延迟的持续时间通常相似（2 - 4小时），表明辐射诱导的G2/M期延迟与细胞放射敏感性之间存在平行关系。这些结果表明，延迟时间可能与细胞接近有丝分裂时存在的未修复损伤水平有关。
