Conjugation of desmethylnaproxen in the rat--a novel acyl glucuronide-sulfate diconjugate as a major biliary metabolite.
The nonsteroidal anti-inflammatory drug naproxen is primarily metabolized in humans by acyl glucuronidation to form naproxen acyl glucuronide and by O-dealkylation to form 6-O-desmethylnaproxen (DMN). DMN contains both carboxy and phenolic groups and has been shown to form acyl glucuronide and sulfate conjugates. This project aimed to investigate whether DMN formed a phenolic glucuronide and diglucuronide(s) (with both the carboxy and phenolic groups glucuronidated). Male Sprague-Dawley rats (300-350 g) with exteriorized bile flow were dosed i.v. with DMN at 50 mg/kg. Four major DMN-related peaks were detected in bile by high-performance liquid chromatography (HPLC) analysis at 225 nm, including the known acyl glucuronide and sulfate conjugates. Selective hydrolyses using acidic and alkaline conditions and digestion with beta-glucuronidase allowed tentative identification of the two unknown peaks as the phenolic glucuronide of DMN and a novel acyl glucuronide-sulfate diconjugate of DMN (i.e., formed by sulfonation of the phenolic group and glucuronidation of the carboxy group). The identities were confirmed by liquid chromatography-tandem mass spectrometry analysis of individual HPLC fractions. Total recovery of the DMN dose was approximately 80%, with the sulfate conjugate (50%) and unchanged DMN (10%) being excreted predominantly in urine and the acyl glucuronide (10%), phenolic glucuronide (6%), and acyl glucuronide-sulfate diconjugate (4%) being excreted predominantly or exclusively in bile. No evidence for a diglucuronide metabolite of DMN was found in either bile or urine of the DMN-dosed rats.
Jaggi
R
R
Centre for Studies in Drug Disposition, The University of Queensland, Clinical Sciences Building, Royal Brisbane Hospital, Brisbane, Queensland, Australia.
Addison
R S
RS
King
A R
AR
Suthers
B D
BD
Dickinson
R G
RG
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry / Q000378:metabolism*; D001646:Bile / Q000378:metabolism*; D020719:Glucuronides / Q000378:metabolism*; D008297:Male; D009288:Naproxen / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013431:Sulfates / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D020719:Glucuronides; D013431:Sulfates; D009288:Naproxen; C034451:desmethylnaproxen