Occurrence of singlet oxygen oxygenation of oleic acid and linoleic acid in the skin of live mice

To assess the contribution of singlet molecular oxygen [O-2 ((1)Delta(g))] to lipid peroxidation in vivo, this study combined gas chromatography-mass spectrometry with thin layer chromatography to analyse peroxidized lipids in the skin of hairless mice. Hydroxyoctadecenoate isomers and unconjugated hydroxyoctadecadienoate isomers derived from peroxidized oleic acid and linoleic acid, respectively, which are specific to O-2 ((1)Delta(g))-dependent oxygenation, were detected in the skin of live mice under ordinary feeding conditions. Short-term ultraviolet A (UVA)-irradiation of the skin in vivo elevated levels of the unconjugated hydroxyoctadecadieno ate isomers significantly, whereas the irradiation of skin homogenate in vitro increased levels of all isomers derived from both O-2 ((1)Delta(g)) and free radical-dependent oxygenation to a much greater extent. This is the first report to demonstrate the occurrence of O-2 ((1)Delta(g))-specific oxygenation of unsaturated fatty acids in living animals.