title: Modest in vivo exposure to solar wavelengths induces a visible absorbing chromophore in Skh-1 mouse epidermis.
abstract: OBJECTIVE
  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/cm(2) (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/cm(2)) 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.
authors.affiliation: Division of Dermatology, Department of Medicine, Morehouse School of Medicine, Atlanta, GA 30310-1700, USA. menterj@msm.edu
authors.forename: Julian M
authors.initials: JM
authors.lastname: Menter
authors.forename: Robert M
authors.initials: RM
authors.lastname: Sayre
authors.forename: John C
authors.initials: JC
authors.lastname: Dowdy
authors.forename: Amir A
authors.initials: AA
authors.lastname: Etemadi
authors.forename: Abrienne M
authors.initials: AM
authors.lastname: Patta
authors.forename: Johnathan
authors.initials: J
authors.lastname: Chappell
authors.forename: Isaac
authors.initials: I
authors.lastname: Willis
mesh_terms: D000042:Absorption; D000818:Animals; D001706:Biopsy; D002863:Chromogenic Compounds / Q000032:analysis / Q000528:radiation effects*; D004396:Coloring Agents; D004307:Dose-Response Relationship, Radiation; D008027:Light; D051379:Mice; D008812:Mice, Hairless; D011829:Radiation Dosage; D012867:Skin / Q000473:pathology / Q000528:radiation effects*; D012880:Skin Pigmentation / Q000528:radiation effects*; D013057:Spectrum Analysis; D014466:Ultraviolet Rays
chemical_list: D002863:Chromogenic Compounds; D004396:Coloring Agents