Action spectrum for cytotoxicity in the UVA- and UVB-wavelength region in cultured lens epithelial cells.

PURPOSE This study was done to quantitate the biologic effects of different wavelengths of radiation in the UVA- and UVB-wavelength region on cultured rabbit lens epithelial cells. METHODS An action spectrum for UV-induced cytotoxicity as measured by colony-forming ability was determined using six different monochromatic wavelengths from 297 to 405 nm in rabbit lens epithelial cell line N/N1003A. Cell survival was determined by clonogenic assay. Fluence rates were monitored with a calibrated radiometer. RESULTS Survival curves show that cell killing was most efficient at 297 nm. After quantum correction, the efficiency of 297-nm radiation in cell killing was 7 times greater than was 302-nm radiation. Radiation at 297 nm was more than 170, 340, 560, and 2000 times as effective in cell killing as 313-, 325-, 334-, and 365-nm radiation, respectively. The action spectrum had a shape similar to the DNA absorption spectrum in the UVB region, suggesting that DNA may be one of the critical targets for damage to the cells. At wavelengths longer than 313 nm, the shape of the action spectrum deviated from the DNA absorption spectrum. CONCLUSIONS Cytotoxicity of UV radiation in cultured lens epithelial cells varies greatly with wavelength within the UVA and UVB regions. Different mechanisms may predominate in the two wavelength regions. Cultured cells may provide a suitable system for investigating the mechanisms by which UV radiation damages lens epithelial cells and leads to cataract formation.