Glutathione and misonidazole: independent or interactive mechanisms of action

The authors have recently studied the effects of prior depletion of glutathione (GSH) by buthionine sulphoxime (BSO) on radiosensitisation by MISO (misonidazole) in anoxic cells (Shrieve et al, 1984). Although results are quite similar to those found by others (Koch, 1983; Clarke et al, 1984) different conclusions have been drawn. The present authors interpret the shift of the log sensitiser concentration versus effect curve to lower doses following GSH depletion to be a result of direct radiosensitising effect of GSH depletion, which is expressed under anoxic conditions in the absence of any exogenous sensitiser. The published data are reanalysed and presented to support this hypothesis. (U.K.)