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  • Title: Abnormal radiosensitizing and cytotoxic properties of ortho-substituted nitroimidazoles.
    Author: Stratford IJ, Hoe S, Adams GE, Hardy C, Williamson C.
    Journal: Int J Radiat Biol Relat Stud Phys Chem Med; 1983 Jan; 43(1):31-43. PubMed ID: 6601069.
    Abstract:
    Various 5-substituted 4-nitroimidazoles have been shown to be much more efficient radiosensitizers and much more toxic than would have been predicted from their electron affinities, as measured by values of one-electron reduction potential, E17. Using Chinese hamster V79 cells in vitro, a comparison has been made with some isomeric 4-substituted 5-nitroimidazoles. These compounds have E17 values some 64mV greater than the 4-nitroimidazoles, yet show much lower sensitizing efficiency and also lower toxicity. Neither series of compounds shows the greater toxicity towards hypoxic cells usually associated with nitroaromatic and nitroheterocyclic compounds. The second-order rate constants, k2, for reaction of these isomeric nitroimidazoles with glutathione and dithiothreitol were determined. Within each series the value of k2 increased with increasing electron affinity, however, the 4-nitroimidazoles were always more reactive than their corresponding 5-nitro isomers. The sensitizing and toxic properties of these compounds may involve depletion of intracellular thiols; this possibility is discussed.
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