Copper as a hypoxic cell sensitizer of mammalian cells.

The sensitizing effect of copper solutions has been studied on mammalian cells. A non-toxic concentration of cupric chloride was reduced under anoxia by irradiation to cuprous chloride, added to anoxic murine leukaemic L5178Y cells and irradiated either under aerobic or anoxic conditions. Sensitization (dose modification factor 1.54) was observed when the cells were irradiated in anoxia (oxygen-free nitrogen gassing). Sensitization was not observed when the cells were irradiated under aerobic conditions (air gassing). Electron spin resonance studies indicated that the conversion Cu II vector Cu I could be brought about by cells incubated under anoxic conditions at room temperature without irradiation.