title: Radiosensitization of cultured mammalian cells by 5-iodouridine.
abstract: Radiosensitization of cultured mammalian cells was studied with halogenated pyrimidines, such as 5-iodouridine or 6-chloropurine, which have been shown to promote bacterial cell lethality when combined with gamma-irradiation. When Chinese hamster cells were exposed to gamma-rays to acidic pH values and the number of colonies was scored after 6 to 11 days of incubation, many more cells were inactivated in the presence of the drug than in its absence. This may be due to radiation-induced cytotoxic iodine radicals from the reagent in the case of 5-iodouridine, because the cells were inactivated efficiently only be contact with the previously-irradiated drug solution. The toxicity of the irradiated drug solution increased remarkably when the pH shifted to acidic side. The radiosensitization and the cytotoxic effects of gamma-irradiated drug solution were not found with 6-chloropurine. This may be the first observation on the lethal effect of chemical radicals on mammalian cells, and it is concluded that radiosensitization with 5-iodouridine does not require the drug incorporation into cellular DNA, at least under the conditions adopted in the present studies.
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured / Q000187:drug effects / Q000528:radiation effects; D002588:Cesium Radioisotopes; D006224:Cricetinae; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D006863:Hydrogen-Ion Concentration; D011687:Purines / Q000031:analogs & derivatives / Q000494:pharmacology; D011830:Radiation Effects; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D013997:Time Factors; D014529:Uridine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D002588:Cesium Radioisotopes; D011687:Purines; D011838:Radiation-Sensitizing Agents; D014529:Uridine