Formation and biliary excretion of glutathione conjugates of bile acids in the rat as shown by liquid chromatography/electrospray ionization-linear ion trap mass spectrometry |
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Authors: | Kuniko Mitamura Yutaka Mitsumoto Mitsuru Sogabe Shigeo Ikegawa |
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Institution: | a Faculty of Pharmaceutical Sciences, Kinki University, Higashi-Osaka 577-8502, Japan b Faculty of Science and Engineering, Kinki University, Higashi-Osaka 577-8502, Japan |
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Abstract: | Acyl-adenylates and acyl-CoA thioesters of bile acids (BAs) are reactive acyl-linked metabolites that have been shown to undergo transacylation-type reactions with the thiol group of glutathione (GSH), leading to the formation of thioester-linked GSH conjugates. In the current study, we examined the transformation of cholyl-adenylate (CA-AMP) and cholyl-coenzyme A thioester (CA-CoA) into a cholyl-S-acyl GSH (CA-GSH) conjugate by rat hepatic glutathione S-transferase (GST). The reaction product was analyzed by liquid chromatography (LC)/electrospray ionization (ESI)-linear ion trap mass spectrometry (MS). The GST-catalyzed formation of CA-GSH occurred with both CA-AMP and CA-CoA. Ursodeoxycholic acid, lithocholic acid, and 2,2,4,4-2H4-labeled lithocholic acid were administered orally to biliary fistula rats, and their corresponding GSH conjugates were identified in bile by LC/ESI-MS2. These in vitro and in vivo studies confirm a new mode of BA conjugation in which BAs are transformed into their GSH conjugates via their acyl-linked intermediary metabolites by the catalytic action of GST in the liver, and the GSH conjugates are then excreted into the bile. |
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Keywords: | Bile acid Acyl-adenylate Acyl-CoA thioester Glutathione S-transferase Glutathione conjugation Electrospray ionization Mass spectrometry |
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