Action spectra for killing and mutation of Chinese hamster cells exposed to mid- and near-ultraviolet monochromatic light

The authors examined the response of Chinese hamster V79 cells to monochromatic light of selected wavelengths in the mid- to near-UV region, using as end points both cell survival and induction of mutations at the HGPRT and Na/K ATPase loci, i.e., resistance to 6-thioguanine (6-TG) and ouabain (OU*A), respectively. As the wavelength increased from 313 nm to 405 nm, the frequency of induction of 6-TG resistant mutants decreased to a greater degree than did cell survival. No mutants resistant to either 6-TG or OUA were induced by 405 nm light, and no mutants resistant to OUA were induced by 365 nm light. The action spectra for cell killing and mutation induction were different; in addition, action spectra for mutations at the HGPRT and the Na/K ATPase loci were quantitatively and qualitatively different from each other. These observations imply major differences in the cellular mechanisms for cell inactivation, induction of 6-TG resistance, and induction of OUA resistance in V79 cells following irradiation with monochromatic light in the near-UV region