title: Quantification of Modified Tyrosines in Healthy and Diabetic Human Urine using Liquid Chromatography/Tandem Mass Spectrometry.
abstract: The quantification of urinary oxidized tyrosines, dityrosine (DiY), nitrotyrosine (NY), bromotyrosine (BrY), and dibromotyrosine (DiBrY), was accomplished by quadruple liquid chromatography-tandem mass spectrometry (LC/MS/MS). The sample was partially purified by solid phase extraction, and was then applied to the LC/MS/MS using multiple-reaction monitoring (MRM) methods. The analysis for the DiY quantification was done first. The residual samples were further butylated with n-butanol/HCl, and the other modified tyrosines were then quantified with isotopic dilution methods. MRM peaks of the modified tyrosines (DiY, NY, BrY, and DiBrY) from human urine were measured and the elution times coincided with the authentic and isotopic standards. The amounts of modified tyrosines in healthy human urine (n = 23) were 8.8 +/- 0.6 (DiY), 1.4 +/- 0.4 (NY), 3.8 +/- 0.3 (BrY), and 0.7 +/- 0.1 (DiBrY) micromol/mol of creatinine, respectively. A comparison of the modified tyrosines with urinary 8-oxo-deoxyguanosine, pentosidine, and N(epsilon)-(hexanoyl)lysine was also performed. Almost all products, except for NY, showed good correlations with each other. The amounts of the modified tyrosines (NY, BrY, and DiBrY) in the diabetic urine were higher than those in the urine from healthy people.
authors.affiliation: School of Human Science and Environment, University of Hyogo, Himeji 670-0092, Japan.
authors.forename: Yoji
authors.initials: Y
authors.lastname: Kato
authors.forename: Natsuko
authors.initials: N
authors.lastname: Dozaki
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nakamura
authors.forename: Noritoshi
authors.initials: N
authors.lastname: Kitamoto
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yoshida
authors.forename: Michitaka
authors.initials: M
authors.lastname: Naito
authors.forename: Masayasu
authors.initials: M
authors.lastname: Kitamura
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Osawa