Abstract
Selected aspects of dobutamine glucuronidation were studied in detail. There are potentially four sites at which dobutamine can be conjugated to glucuronic acid. Three of the four dobutamine monoglucuronides that can be formed were enzymatically synthesized using pig liver microsomes, isolated, and characterized by tandem mass spectrometry, and 1H and 13C NMR spectroscopy. Analysis of dobutamine glucuronidation by liver microsomes from various sources revealed large variability in the ratios of the three regioisomers. Interestingly, catecholic dobutamine meta-O-glucuronide, by far the major product synthesized with human liver microsomes, was only a minor product for rat liver microsomes. Rabbit liver microsomes yielded diglucuronides, in addition to monoglucuronides. Activities of individual recombinant human UDP-glucuronosyltransferases (UGTs) were investigated, and the results suggested that dobutamine glucuronidation in the human liver is mainly carried out by UGTs 2B7 and 1A9. Among the extrahepatic UGTs, the formation of monoglucuronides, mainly catecholic meta-O-glucuronide, by UGTs 1A7 and 1A8 was similar to that by 1A9, whereas UGT1A10 also efficiently catalyzed the formation of catecholic dobutamine para-O-glucuronide.
Footnotes
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Sources of financial support were the Ministry of Education (Finnish Graduate School in Pharmaceutical Research), the National Technology Agency of Finland (TEKES), and the Academy of Finland (project 207535).
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.104.002139.
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ABBREVIATIONS: UGT, UDP-glucuronosyltransferase; glu, glucuronic acid; MS/MS, tandem mass spectrometry; UDPGA, uridine-5′-diphosphoglucuronic acid; HPLC, high-performance liquid chromatography; DMSO, dimethyl sulfoxide; LC, liquid chromatography; MS, mass spectrometry; DQFCOSY, double quantum filtered correlated spectroscopy; NOE, nuclear Overhauser enhancement; NOESY, NOE spectroscopy; HSQC, heteronuclear single quantum coherence; HMBC, heteronuclear multiple bond correlation.
- Received September 1, 2004.
- Accepted January 28, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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