Chan G L, Little J B
Mutat Res. 1981 Nov;84(1):191-201. doi: 10.1016/0027-5107(81)90062-2.
We measured the clonogenic survival response of cultured mouse 10T1/2 cells exposed to UV light and caffeine post-treatment. When 0.5 and 1 mM caffeine were present for 24 h immediately following UV, the D0 values of the biphasic survival curves suggest that one subpopulation was sensitized and one subpopulation was protected from killing by UV light. A cloned survivor from the radioprotected subpopulation responded to UV plus caffeine in identical manner as the parent cells. When the caffeine exposure was prolonged to 48 h, only the radiosensitizing effect was observed. Two demethylated analogs of caffeine were also tested. The response of 10T1/2 cells to 1 mM theophylline present for 24 h after UV irradiation was approximately the same as that for the same treatment with 1 mM caffeine. However, prolonging the theophylline exposure to 48 h failed to produce the same kind of potentiation of cell killing as that observed for caffeine. Xanthine by itself was as toxic to 10T1/2 cells as caffeine, but had no synergistic effect as caffeine when given to UV-irradiated cells for 24 or 48 h. It is therefore unlikely that all the effects of caffeine on UV-irradiated cells are mediated by its demethylated metabolites.
我们测量了经紫外线照射及咖啡因处理后的培养小鼠10T1/2细胞的克隆形成存活反应。当在紫外线照射后立即加入0.5 mM和1 mM咖啡因并持续24小时时，双相存活曲线的D0值表明，一个亚群被敏化，而另一个亚群受到保护，免受紫外线杀伤。来自放射保护亚群的一个克隆存活细胞对紫外线加咖啡因的反应与亲代细胞相同。当咖啡因暴露时间延长至48小时时，仅观察到放射增敏作用。还测试了咖啡因的两种去甲基类似物。紫外线照射后加入1 mM茶碱并持续24小时，10T1/2细胞的反应与相同处理下加入1 mM咖啡因时大致相同。然而，将茶碱暴露时间延长至48小时未能产生与咖啡因相同的细胞杀伤增强作用。黄嘌呤本身对10T1/2细胞的毒性与咖啡因相同，但在紫外线照射的细胞中加入24或48小时时，没有与咖啡因相同的协同作用。因此，咖啡因对紫外线照射细胞的所有作用不太可能都由其去甲基代谢产物介导。
