[Comparative studies on the radiosensitizing action of 4-nitroimidazole and metronidazole (author's transl)]

After the 2-nitroimidazole derivatives, misonidazole, and the 5-nitroimidazole derivative, metronidazole, had been tried in clinical radiotherapy, it seemed necessary to test substances from the group of 4-nitroderivatives of the imidazole on their effectiveness as hypoxic radiosensitizers. Therefore, the influence of 1-(2'-hydroxyethyl)-2-methyl-4-nitroimidazole vs. metronidazole on the semiconservative DNA synthesis prior to the following irradiation on leukemia cells L5178Y, on the reproductive capacity in V-70 cells on the Chinese hamster and on radiation-induced inhibition of tumour growth has been investigated in comparative experiments. The results showed a considerably lower inhibitory effect on DNA synthesis by 4-nitroimidazole compared with metronidazole. Neither substance has any influence on radiation-induced DNA synthesis under oxic conditions. Under hypoxia the 4-nitroimidazole derivative shows a little stronger radiosensitizing action than metronidazole. The radiation-induced decrease of the survival rate of V-79 cells is not influenced by either substance in well oxygenized cells, while being increased to approximately the same degree in hypoxic cultures. The radiation-induced inhibition of breast cancer growth in the 1st transplantation passage of C3H inbred mice is potentiated by 4-nitroimidazole in a similar way as by metronidazole.