Modest in vivo exposure to solar wavelengths induces a visible absorbing chromophore in Skh-1 mouse epidermis
In the previous work, we correlated epidermal hyperplasia with increased epidermal absorption in the 250–400 nm region. During a recent review of that work, the apparent formation of a chromophore, with absorption slightly longer than 400 nm, in the epidermis of irradiated animals was noted. In this study, we have extended the transmission measurement to include the 250–800 nm region. Methods:
Age-matched Skh-1 hairless mice were separated into three groups. One group was irradiated with 6.3 J/cm2 (0.9 minimal erythemal dose; MED) of solar simulating ultraviolet radiation (SSUVR) five times/week for 2 weeks, then increased to 1.1 MED (7.1 J/cm2) for two additional weeks (20-day group). A second 10-day group, added halfway through the protocol, was irradiated with 0.9 MED five times/week for 2 weeks. The control group received no UV irradiation. Routine H&E staining and epidermal absorption spectral analysis were carried out on biopsy specimens from each animal. Results:
This work confirms the development or enhancement of a visible chromophore with a maximum absorption at ca 412 nm. This peak appears to be radiation dose dependent. It can be discerned in both the groups, albeit more prominently in the 20-day animals. The absorption is sufficiently strong to impart a yellow to reddish appearance to skin viewed in full spectrum visible light. Conclusions:
Accumulation of such a chromophore in humans may contribute to the coloration of chronically exposed skin. The absorption strength and wavelength location of the peak is strongly suggestive of a heme-like compound. We are currently conducting experiments to further characterize this chromophore.
Document Type: Research Article
Affiliations: 1: Rapid Precision Testing Laboratories, Cordova, TN, USA, 2: Department of Anatomy, Morehouse School of Medicine, Atlanta, GA, USA 3: Division of Dermatology, Department of Medicine, Morehouse School of Medicine, Atlanta, GA USA,
Publication date: 2004-10-01