title: Studies on the metabolism of tolmetin to the chemically reactive acyl-coenzyme A thioester intermediate in rats.
abstract: Carboxylic acids may be metabolized to acyl glucuronides and acyl-coenzyme A thioesters (acyl-CoAs), which are reactive metabolites capable of reacting with proteins in vivo. In this study, the metabolic activation of tolmetin (Tol) to reactive metabolites and the subsequent formation of Tol-protein adducts in the liver were studied in rats. Two hours after dose administration (100 mg/kg i.p.), tolmetin acyl-CoA (Tol-CoA) was identified by liquid chromatography-tandem mass spectrometry in liver homogenates. Similarly, the acyl-CoA-dependent metabolites tolmetin-taurine conjugate (Tol-Tau) and tolmetin-acyl carnitine ester (Tol-Car) were identified in rat livers. In a rat bile study (100 mg/kg i.p.), the S-acyl glutathione thioester conjugate was identified, providing further evidence of the formation of reactive metabolites such as Tol-CoA or Tol-acyl glucuronide (Tol-O-G), capable of acylating nucleophilic functional groups. Three rats were treated with clofibric acid (150 mg/kg/day i.p. for 7 days) before dose administration of Tol. This resulted in an increase in covalent binding to liver proteins from 0.9 nmol/g liver in control rats to 4.2 nmol/g liver in clofibric acid-treated rats. Similarly, levels of Tol-CoA increased from 0.6 nmol/g to 4.4 nmol/g liver after pretreatment with clofibric acid, whereas the formation of Tol-O-G and Tol-Tau was unaffected by clofibric acid treatment. However, Tol-Car levels increased from 0.08 to 0.64 nmol/g after clofibric acid treatment. Collectively, these results confirm that Tol-CoA is formed in vivo in the rat and that this metabolite can have important consequences in terms of covalent binding to liver proteins.
authors.affiliation: Department of Pharmaceutics and Analytical Chemistry, the Danish University of Pharmaceutical Sciences, Copenhagen, Denmark. jqgo@novonordisk.com
authors.forename: Jørgen
authors.initials: J
authors.lastname: Olsen
authors.forename: Chunze
authors.initials: C
authors.lastname: Li
authors.forename: Christian
authors.initials: C
authors.lastname: Skonberg
authors.forename: Inga
authors.initials: I
authors.lastname: Bjørnsdottir
authors.forename: Ulrik
authors.initials: U
authors.lastname: Sidenius
authors.forename: Leslie Z
authors.initials: LZ
authors.lastname: Benet
authors.forename: Steen Honoré
authors.initials: SH
authors.lastname: Hansen
mesh_terms: D000214:Acyl Coenzyme A / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001646:Bile / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D002995:Clofibric Acid / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D008099:Liver / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D008297:Male; D015394:Molecular Structure; D051381:Rats; D017207:Rats, Sprague-Dawley; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D014046:Tolmetin / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000214:Acyl Coenzyme A; D000894:Anti-Inflammatory Agents, Non-Steroidal; D002995:Clofibric Acid; D014046:Tolmetin