From pharmacokinetic studies in animals and man and in vitro binding studies we have shown that acyl glucuronide metabolites of bilirubin and zomepirac (ZomaxR) react nonenzymicly with serum albumin to give covalent adducts. For bilirubin, substantial quantities of adducts are formed only when normal excretion of bilirubin glucuronides in bile is impaired as in patients with cholestatic jaundice. With zomepirac, however, covalent binding to serum proteins via the acyl glucuronide occurs even in healthy humans after a single drug dose. If plasma clearance of zomepirac and its glucuronide is reduced in humans by concurrent probenecid administration, or in animals by experimentally-induced cholestasis, formation of zomepirac-albumin adducts increases. These observations coupled with the known chemical reactivity of acyl glucuronides and the common occurrence of such compounds in vivo as drug metabolites, suggest that covalent binding of carboxylic acids to albumin, or to other proteins and macromolecules, via glucuronide metabolites may be a general phenomenon of wide significance. We propose to test this hypothesis, which if true could have major pharmacological and toxicological significance, and to determine whether factors, such as age, disease states, chronic dosing and the stability of the glucuronide, influence the in vivo exposure of animals or humans to these reactive acyl glucuronides. Purified acyl glucuronides from several acidic drugs (eg. salicylate, ibuprofen, diflunisal, furosemide, tolmetin, zomepirac and benoxaprofen) will be incubated with serum albumin in vitro and the extent of covalent binding will be measured. Zomepirac glucuronide and other reactive acyl glucuronides will be examined for similar binding to microsomal protein, collagen, ligandin and nucleic acids in vitro. The amino acid residue which reacts with zomepirac glucuronide and the mechanism for the binding will be examined. Factors which influence the exposure to the reactive glucuronides in vivo will be examined by testing the effects of reduced excretion (renal failure and cholestasis); increased rate of glucuronide formation (phenobarbital); and reduced hydrolysis by esterase inhibition (PMSF, pyridostigmine), on the extent of irreversible binding in vivo in animals. Finally, studies will be conducted with young, healthy human volunteers and elderly patients to determine if covalent binding occurs in vivo for acidic drugs presently in clinical use, and whether an increase in the extent of covalent binding is correlated with exposure to the acyl glucuronide.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM036633-03
Application #
3291005
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1986-04-01
Project End
1989-11-30
Budget Start
1988-04-01
Budget End
1989-11-30
Support Year
3
Fiscal Year
1988
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Pharmacy
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Horng, Howard; Benet, Leslie Z (2013) The nonenzymatic reactivity of the acyl-linked metabolites of mefenamic acid toward amino and thiol functional group bionucleophiles. Drug Metab Dispos 41:1923-33
Horng, Howard; Benet, Leslie Z (2013) Characterization of the acyl-adenylate linked metabolite of mefenamic Acid. Chem Res Toxicol 26:465-76
Grillo, Mark P; Wait, Jill C M; Tadano Lohr, Michelle et al. (2010) Stereoselective flunoxaprofen-S-acyl-glutathione thioester formation mediated by acyl-CoA formation in rat hepatocytes. Drug Metab Dispos 38:133-42
Grillo, Mark P; Hua, Fengmei; March, Kristi L et al. (2008) Gamma-glutamyltranspeptidase-mediated degradation of diclofenac-S-acyl-glutathione in vitro and in vivo in rat. Chem Res Toxicol 21:1933-8
Li, Chunze; Grillo, Mark P; Badagnani, Ilaria et al. (2008) Differential effects of fibrates on the metabolic activation of 2-phenylpropionic acid in rats. Drug Metab Dispos 36:682-7
Olsen, Jorgen; Li, Chunze; Skonberg, Christian et al. (2007) Studies on the metabolism of tolmetin to the chemically reactive acyl-coenzyme A thioester intermediate in rats. Drug Metab Dispos 35:758-64
Olsen, Jorgen; Li, Chunze; Bjornsdottir, Inga et al. (2005) In vitro and in vivo studies on acyl-coenzyme A-dependent bioactivation of zomepirac in rats. Chem Res Toxicol 18:1729-36
Wu, Chi-Yuan; Benet, Leslie Z (2005) Predicting drug disposition via application of BCS: transport/absorption/ elimination interplay and development of a biopharmaceutics drug disposition classification system. Pharm Res 22:11-23
Chang, Jae H; Benet, Leslie Z (2005) Glucuronidation and the transport of the glucuronide metabolites in LLC-PK1 cells. Mol Pharm 2:428-34
Mohri, Kiminori; Okada, Kenji; Benet, Leslie Z (2005) Stereoselective taurine conjugation of (R)-benoxaprofen enantiomer in rats: in vivo and in vitro studies using rat hepatic mitochondria and microsomes. Pharm Res 22:79-85

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