SURVIVAL OF CLOUDMAN MOUSE MELANOMA-CELLS AFTER IRRADIATION BY SOLAR WAVELENGTHS OF LIGHT

A number of variants of Cloudman S91 mouse melanoma cells that differ with respect to the amount of pigment produced are available for study , In this report, we compare the photobiological responses of S91/amel , which contains about 1 pg of melanin per cell, with S91/I3, which co ntains about 3 pg/cell, Earlier studies had shown that UVC induced mor e oxidative damage (in the form of thymine glycols) in cell line S91/I 3 than in S9l/amel and that cell line S91/amel was more resistant to k illing by UVC than S91/I3. The present study finds that S91/amel cells are also relatively resistant to killing by near monochromatic UVB fr om a Philips TL01 fluorescent lamp and by near monochromatic UVA from a Philips HPW125 lamp. However, when the cells are irradiated with a W estinghouse FS20 polychromatic lamp, the S91/I3 cells are more resista nt than the S91/amel cells, These findings cannot be explained on the basis of pigment induction because in S91/I3 this is about the same af ter UVB and FS20, although the maximum is reached earlier after UVB, N or can our findings be explained on the basis of pyrimidine dimer form ation, which is comparable in the two cell lines regardless of the typ e of irradiation, These results suggest that, with a pigment such as m elanin, which absorbs light across the visible and ultraviolet ranges of the spectrum, cellular responses to monochromatic light do not nece ssarily predict responses to polychromatic mixtures.