title: BCNU-induced sister chromatid exchanges are increased by X irradiation.
abstract: We have studied the effect on sister chromatid exchange (SCE) induction in 9L rat brain tumor cells caused by combination treatment with BCNU and X rays. Over the dose and concentration ranges used in these experiments, BCNU induced relatively large numbers of SCEs, while X rays induced few SCEs. When cells were X irradiated immediately after BCNU treatment, the number of SCEs induced was greater than the number of SCEs expected by adding the number of SCEs induced by each agent alone; the number of SCEs induced as a result of this BCNU-X-ray interaction increased as the concentration of BCNU and/or dose of X rays increased. When the addition of bromodeoxyuridine was delayed from 0 to 16 hr after BCNU treatment, the number of SCEs induced declined to control levels by 16 hr. If X irradiation was delayed for up to 16 hr after BCNU treatment the same pattern of decrease was observed; the number of SCEs induced at each time point, however, was greater than that induced by BCNU and X rays alone. X irradiation from 0-16 hr before BCNU treatment produced the same number of SCEs as that produced by BCNU alone. Thus the SCE assay is capable of detecting a drug-X-ray interaction in mammalian cells and provides a sensitive means of studying the sequencing and timing that leads to the interaction.
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000188:drug therapy / Q000532:radiotherapy; D002330:Carmustine / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D003434:Crossing Over, Genetic / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D008677:Metaphase / Q000187:drug effects / Q000528:radiation effects; D051381:Rats; D012854:Sister Chromatid Exchange / Q000187:drug effects* / Q000528:radiation effects; D013997:Time Factors
chemical_list: D002330:Carmustine