Millar B C, Jenkins T C, Smithen C E, Jinks S
Radiat Res. 1985 Jan;101(1):111-22.
Bothtrans-N,N'-bis(2,2,6,6-tetramethyl-1-oxyl-4-piperidinyl)-1, 2-diaminocyclopropane[Ro31-2269] and its cis isomer [Ro 31-2778] selectively sensitized hypoxic Chinese hamster cells, line V-79-753B, to radiation by decreasing both the D0 value and extrapolation number, whereas a related dibasic monoradical Ro 31-2655 decreased D0 alone. Although sensitization was maximal after a 1-hr cell-drug contact time, cells continued to accumulate both Ro 31-2269 and Ro 31-2778 when this contact time was increased up to 3 hr. There was no evidence for competition between either biradical and 2,2,6,6-tetramethyl-4-piperidinol-N-oxyl (TMPN) at equimolar concentration or biradical and 0.82 microM oxygen when cells were equilibrated with the biradicals for 3 hr prior to irradiation in the presence of mixtures of either oxygen and biradical, TMPN and biradical, or TMPN alone. Furthermore, when cells were equilibrated with an equimolar radical concentration of the trans isomer Ro 31-2269 and TMPN for 1 hr prior to irradiation in the presence of the mixture, there was no appreciable effect on sensitization of the slope of the hypoxic cell survival curve, but shoulder modification was reduced. When cells were equilibrated with the trans isomer Ro 21-2269 prior to irradiation in combination with 2.92 microM oxygen, cell survival was similar to that seen for cells irradiated with this concentration of oxygen alone. Examination of the plasma membrane from cells equilibrated with the trans biradical Ro 31-2269 showed that the drug accumulated in the membrane when compared with the concentration found in whole cells. Experiments with the conformationally-unrestricted biradical bis(2,2,6,6-tetramethyl-1-oxy-4-piperidinyl) succinate [Ro 03-6061] showed that when cells were equilibrated with the compound for 1 hr prior to irradiation in hypoxia in the presence of a mixture containing an equimolar radical concentration of TMPN, there was an increase in both the slope and the extrapolation number compared with values for hypoxic cells irradiated in the presence of this biradical alone. Furthermore, when cells which had been equilibrated with Ro 03-6061 were washed free of the drug, there was a residual decrease in both the D0 and extrapolation number of the hypoxic cell survival curve for at least 3 hr after removal of the compound. The results are discussed in terms of a model to account for sensitization by these compounds.
反式-N,N'-双(2,2,6,6-四甲基-1-氧代-4-哌啶基)-1,2-二氨基环丙烷[Ro31-2269]及其顺式异构体[Ro 31-2778]通过降低D0值和外推数，选择性地使缺氧的中国仓鼠细胞系V-79-753B对辐射敏感，而相关的二元单自由基Ro 31-2655仅降低D0。尽管在细胞与药物接触1小时后敏化作用最大，但当该接触时间延长至3小时时，细胞仍继续积累Ro 31-2269和Ro 31-2778。没有证据表明在等摩尔浓度下，双自由基与2,2,6,6-四甲基-4-哌啶醇-N-氧基(TMPN)之间存在竞争，也没有证据表明在辐射前细胞与双自由基平衡3小时后，双自由基与0.82 microM氧气之间存在竞争，此时细胞处于氧气和双自由基、TMPN和双自由基或单独的TMPN混合物中。此外，当细胞在混合物存在下辐射前与反式异构体Ro 31-2269和TMPN的等摩尔自由基浓度平衡1小时时，对缺氧细胞存活曲线斜率的敏化作用没有明显影响，但肩部修饰减少。当细胞在辐射前与反式异构体Ro 21-2269平衡并与2.92 microM氧气结合时，细胞存活率与仅用该浓度氧气辐射的细胞相似。对与反式双自由基Ro 31-2269平衡的细胞的质膜检查表明，与全细胞中发现的浓度相比，该药物在膜中积累。用构象不受限制的双自由基双(2,2,6,6-四甲基-1-氧基-4-哌啶基)琥珀酸酯[Ro 03-6061]进行的实验表明，当细胞在缺氧条件下辐射前与该化合物平衡1小时，且存在含等摩尔自由基浓度的TMPN的混合物时，与仅在该双自由基存在下辐射的缺氧细胞的值相比，斜率和外推数均增加。此外，当用Ro 03-6061平衡过的细胞洗去药物后，在去除该化合物后至少3小时内，缺氧细胞存活曲线的D0和外推数仍有残留下降。根据一个解释这些化合物敏化作用的模型对结果进行了讨论。
