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Abstract
In previous studies with albino hairless mice, we showed that broadband ultraviolet A radiation (UVA) damages dermal connective tissue. Recent studies examined segments of the UVA waveband in detail. In one, mice were irradiated with a solar simulator using Schott WG filters with different 50% cutoff points in the UVA region. Biopsies were examined at the following dosages: WG 335 (500,1000, 2000 J/cm2); WG 345 (800,1600,3200 J/cm2); WG 360 (2000,4000 J/cm2). A second study utilized a high-intensity source filtered to eliminate wavelengths < 340 nm. Biopsies were examined at 500,1000, 2000,4000, and 8000 J/cms2. Histochemical stains were used to examine elastic fibers, collagen, and glycosaminoglycans. Collagen appeared damaged mainly by the shorter wavelengths, while all wavelengths induced elastic fiber hyperplasia and increased glycosaminoglycans. These changes required high but realistically obtainable doses. UVA is a weak carcinogen but in a third study its addition to low-dose UVB caused significant enhancement of tumorigenesis.