On the mechanism of BUdR sensitization: a pulse radiolysis study of one electron transfer in nucleic-acid derivatives.
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Biomedical subjects
Publications and source records attributed to G E Adams.
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In principle, radiation sensitizers with therapeutic ratios greater than that of misonidazole can be obtained either by increasing sensitizing efficiency, decreasing toxicity or preferably both. This paper illustrates, firstly that a 5-nitroimidazole (S73-0662) with an electron affinity close to that of metronidazole shows sensitizing efficiency similar to misonidazole both in vitro and in vivo. The suggestion is made that this compound should receive a detailed toxicological study to ascertain if its toxicity is lower than misonidazole. Secondly, Imuran, a 5-substituted 4-nitroimidazole and one of a series of compounds which show sensitizing efficiencies in vitro much greater than would be predicted from electron affinity considerations, also shows good sensitization in vivo. Compounds in this series are generally metabolically unstable and the positive results with Imuran in vivo provide a direction for future synthesis of novel sensitizers.
Misonidazole, metronidazole and nitrofurazone can enhance the cytotoxicity of melphalan in vitro if the cells are subjected to a hypoxic pretreatment with the drug prior to exposure of melphalan in air. Potentiation of melphalan is dependent upon the concentrations of the nitro compound and the duration of the hypoxic pretreatment. On a concentration basis, nitrofurazone was most effective at enhancing melphalan toxicity and metronidazole was the least effective. This potentiating activity correlates with the electron affinity of each drug.