title: Identification of bile acid S-acyl glutathione conjugates in rat bile by liquid chromatography/electrospray ionization-linear ion trap mass spectrometry.
abstract: Acyl-adenylates and acyl-CoA thioesters of bile acids (BAs) are reactive acyl-linked metabolites that have been shown to acylate the thiol group of glutathione (GSH); the reaction is catalyzed by glutathione S-transferase (GST) and the product is a thioester-linked BA-GSH conjugate. Such GSH conjugates are present in bile in lithocholic acid and ursodeoxycholic acid dosed-rats. To determine whether such novel BA-GSH conjugates are present in the bile of normal rats, we first synthesized the GSH conjugates of the major and minor biliary BAs of the rat and defined their MS and proton NMR properties. We then analyzed the BA-GSH composition in the bile of anesthetized biliary fistula rats by means of liquid chromatographic separation and electrospray ionization-linear ion trap mass spectrometric detection in negative- and positive-ion scan modes, monitoring characteristic transitions of the analytes. GSH conjugates of cholic, ω-muricholic, hyodeoxycholic, deoxycholic, 12-oxolithocholic, and lithocholic acids were present with concentrations in the range of 1.4-2.8 nmol/ml, some four orders of magnitude less than those of natural BA N-acyl amidates. Our results indicate that BA-GSH conjugates are formed and excreted in bile in the healthy rat, although this novel mode of BA conjugation is a very minor pathway.
authors.affiliation: Faculty of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-osaka 577-8502, Japan.
authors.forename: Kuniko
authors.initials: K
authors.lastname: Mitamura
authors.forename: Naohiro
authors.initials: N
authors.lastname: Hori
authors.forename: Takashi
authors.initials: T
authors.lastname: Iida
authors.forename: Alan F
authors.initials: AF
authors.lastname: Hofmann
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ikegawa
mesh_terms: D000818:Animals; D001646:Bile / Q000737:chemistry*; D001647:Bile Acids and Salts / Q000737:chemistry*; D002853:Chromatography, Liquid; D005978:Glutathione / Q000138:chemical synthesis / Q000737:chemistry*; D008297:Male; D008968:Molecular Conformation; D051381:Rats; D017208:Rats, Wistar; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism
chemical_list: D001647:Bile Acids and Salts; D005978:Glutathione