Action spectra for ultraviolet photosensitized killing of mammalian cells by misonidazole and para-nitroacetophenone

V-79 Chinese hamster fibroblasts in monolayer culture were exposed to ultraviolet radiation at 313, 334, 365, 380 and 405 nm in the presence of either misonidazole or para-nitroacetophenone, drugs which act as both photosensitizers and radiosensitizers of cell killing. Survival was measured by a colony-forming assay. The resulting action spectra for cell death photosensitized by the drugs (the reciprocals of the exposures required at each wavelength to reduce cell survival to a given level) closely match their absorption spectra over a range of three orders of magnitude. These results demonstrate that cells can be killed upon excitation of misonidazole or para-nitroacetophenone in the absence of any other types of energy deposition or biomolecular damage.