title: Action spectra for the trans to cis photoisomerisation of urocanic acid in vitro and in mouse skin.
abstract: Urocanic acid (UCA) is a major UV chromophore in the upper layers of the skin where it is found predominantly as the trans isomer. UV irradiation induces photoisomerisation of trans-UCA to cis-UCA which has been shown to mimic some of the immunosuppressive properties of UV exposure. We examined the wavelength dependence for trans-UCA to cis-UCA photoisomerisation in vitro and in mouse skin in vivo over the spectral range 270-340 nm. The resulting action spectra were very similar with maximal effectiveness at 300-315 nm and equal activity at 270 nm and 325-330 nm, demonstrating that UVA-II radiation (320-340 nm) is efficient at UCA photoisomerisation. These action spectra differed markedly from the trans-UCA absorption spectrum in vitro and also the reported action spectrum for UV suppression of contact hypersensitivity in mice. These findings suggest that the relationship between cis-UCA formation in skin and UV-induced immunosuppression may be complex.
authors: Photobiology Unit, Ninewells Hospital, University of Dundee, Scotland.
authors: N K
authors: NK
authors: Gibbs
authors: M
authors: M
authors: Norval
authors: N J
authors: NJ
authors: Traynor
authors: M
authors: M
authors: Wolf
authors: B E
authors: BE
authors: Johnson
authors: J
authors: J
authors: Crosby
mesh_terms: D000818:Animals; D005260:Female; D007536:Isomerism; D051379:Mice; D008812:Mice, Hairless; D012867:Skin / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014560:Urocanic Acid / Q000528:radiation effects*
chemical_list: D014560:Urocanic Acid