Freyer J P, Jarrett K, Carpenter S, Raju M R
Cellular and Molecular Biology Group, Los Alamos National Laboratory, New Mexico 87545.
Radiat Res. 1991 Sep;127(3):297-307.
There is still controversy over whether the oxygen enhancement ratio (OER) varies as a function of dose and cell cycle phase. In the present study, the OER has been measured as a function of survival level and cell cycle phase using volume flow cell sorting. This method allows both the separation of cells in different stages of the cycle from an asynchronously growing population, and the precise plating of cells for accurate measurements at high survival levels. We have developed a cell suspension gassing and sampling system which maintained an oxygen tension less than 20 ppm throughout a series of sequential radiation doses. For both radiation-resistant cells (CHO-K1) and a radiation-sensitive clone (CHO-xrs6), we could separate relatively pure populations of G1-phase, G1/S-boundary, S-, and G2-phase cells. Each cell line showed a typical age response, with cells at the G1/S-phase boundary being 4 (CHO-K1) to 12 (CHO-xrs6) times more sensitive than cells in the late S phase. For both cell lines, G1-phase cells had an OER of 2.3-2.4, compared to an OER of 2.8-2.9 for S-phase and 2.6-2.7 for G2-phase cells. None of these age fractions showed a dependence of OER on survival level. Asynchronously growing cells or cells at the G1/S-phase boundary had an OER similar to that of G1-phase cells at high survival levels, but the OER increased with decreasing survival level to a value near that of S-phase cells. These results suggest that the decrease in OER at high survival levels for asynchronous cells may be due to differences in the OERs of the inherent cell age subpopulations. For cells in one cell cycle stage, oxygen appears to have a purely dose-modifying effect.
关于氧增强比（OER）是否随剂量和细胞周期阶段而变化仍存在争议。在本研究中，使用体积流式细胞分选技术测量了作为存活水平和细胞周期阶段函数的OER。该方法既可以从异步生长的群体中分离出处于细胞周期不同阶段的细胞，又可以精确接种细胞以在高存活水平下进行准确测量。我们开发了一种细胞悬液通气和采样系统，在一系列连续辐射剂量过程中，该系统能将氧张力维持在20 ppm以下。对于抗辐射细胞（CHO-K1）和辐射敏感克隆（CHO-xrs6），我们都能分离出相对纯的G1期、G1/S边界期、S期和G2期细胞群体。每个细胞系都表现出典型的年龄反应，处于G1/S期边界的细胞比S期后期的细胞敏感4（CHO-K1）至12（CHO-xrs6）倍。对于这两个细胞系，G1期细胞的OER为2.3 - 2.4，相比之下，S期细胞的OER为2.8 - 2.9，G2期细胞的OER为2.6 - 2.7。这些年龄组分均未显示OER对存活水平的依赖性。在高存活水平下，异步生长的细胞或处于G1/S期边界的细胞的OER与G1期细胞相似，但随着存活水平降低，OER增加至接近S期细胞的值。这些结果表明，异步细胞在高存活水平下OER的降低可能是由于固有细胞年龄亚群的OER差异所致。对于处于一个细胞周期阶段的细胞，氧似乎仅具有剂量修饰作用。
