title: Potential role of conjugated bilirubin and copper in the metabolism of lipid peroxides in bile.
abstract: Conjugated bilirubin and copper ions at their physiological concentrations in bile may play an important role in hydroperoxide and other detoxification. Conjugated bilirubin may also be an important chain-breaking antioxidant preventing lipid peroxidation. Bilirubin ditaurine (BR-DT), a water-soluble model compound of conjugated bilirubin, completely prevents the peroxyl radical-induced oxidation of phosphatidylcholine in either multilamellar liposomes or micelles. This antioxidant activity is associated with the bilirubin moiety of BR-DT, since taurine alone is inefficient in scavenging peroxyl radicals. The number of peroxyl radicals trapped per molecule of BR-DT is 1.9, compared to 4.7 trapped per molecule of biliverdin, the water-soluble physiological precursor of bilirubin. Peroxyl radical-induced oxidation of BR-DT results in a spectral shift in maximal absorbance toward shorter wavelengths; biliverdin is not formed as a major oxidation product. BR-DT, but neither taurine nor biliverdin, greatly accelerates the cupric ion-catalyzed decomposition of linoleic acid hydroperoxide. In the presence of ferric ion, BR-DT shows no lipid hydroperoxide-degrading activity. Addition of cupric ion to BR-DT results in formation of a complex with spectral features similar to that of a biliverdin-cupric ion complex, indicating that BR-DT and cupric ion undergo redox reactions.
mesh_terms: D001646:Bile / Q000378:metabolism*; D001663:Bilirubin / Q000031:analogs & derivatives* / Q000502:physiology; D003300:Copper / Q000502:physiology*; D008658:Inactivation, Metabolic; D008054:Lipid Peroxides / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000378:metabolism; D013654:Taurine / Q000031:analogs & derivatives* / Q000502:physiology
chemical_list: D008054:Lipid Peroxides; D008081:Liposomes; D010713:Phosphatidylcholines; D013654:Taurine; D003300:Copper; C054146:bilirubin ditaurine; D001663:Bilirubin