Common fluorescent sunlamps are an inappropriate substitute for sunlight

Fluorescent sunlamps are commonly employed as convenient sources in photobi ology experiments. The ability of Kodacel to filter photobiologically irrel evant UVC wavelengths has been described. Yet there still remains a major u naddressed issue-the over representation of UVB in the output. The shortest terrestrial solar wavelengths reaching the surface are similar to 295 nm w ith the 295-330 nm range comprising similar to 4% of the solar UV irradianc e, in Kodacel-filtered sunlamps, 47% of the UV output falls in this range. Consequently, in studies designed to understand skill photobiology after so lar exposure, the use of these unfiltered sunlamps may result in misleading , or even incorrect conclusions. To demonstrate the importance of using an accurate representation of the UV portion of sunlight, the ability of diffe rent ultraviolet radiation (UVR) sources to induce the expression of a repo rter gene was assayed. Unfiltered fluorescent sunlamps (FS lamps) induce op timal chloramphenicol acetyltransferase (CAT) activity at apparently low: d oses (10-20 J/cm(2)). Filtering the FS lamps with Kodacel raised the delive red dose for optimal CAT activity to 50-60 mJ/cm(2), With the more solar-li ke UVA-340 lamps somewhat lower Levels of CAT activities were induced even though the apparent delivered doses were significantly greater than for eit her the FS or Kodacel-filtered sunlamp (KFS lamps). When DNA from parallel- treated cells was analyzed for photoproduct formation by a radioimmuneassay , it was shown that the induction of CAT activity correlated with the level of induced photoproduct formation regardless of the source employed.