title: Pulegone mediated hepatotoxicity: evidence for covalent binding of R(+)-[14C]pulegone to microsomal proteins in vitro.
abstract: Incubation of R(+)-[14C]pulegone with rat liver microsomes in the presence of NADPH resulted in covalent binding of radioactive material to macromolecules. Covalent binding was much higher in phenobarbital-treated microsomes as compared to 3-methylcholanthrene treated or control microsomes. The Km and Vmax of covalent binding was 0.4 mM and 1.7 nmol min-1 mg-1, respectively. Covalent binding was drastically inhibited (93%) in the presence of piperonyl butoxide. Antibodies to phenobarbital-induced cytochrome P-450 and NADPH-cytochrome P-450 reductase inhibited covalent binding to an extent of 72% and 47%, respectively. Cysteine and semicarbazide also inhibited NADPH dependent binding of radiolabel from R(+)-[14C]pulegone to microsomal proteins. The results suggest the involvement of liver microsomal cytochrome P-450 in the bioactivation of R(+)-pulegone to reactive metabolite(s) which might be responsible for covalent binding to macromolecules resulting in toxicity.
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science, Bangalore.
authors.forename: K M
authors.initials: KM
authors.lastname: Madyastha
authors.forename: B
authors.initials: B
authors.lastname: Moorthy
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D000081005:Cyclohexane Monoterpenes; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000473:pathology*; D008610:Menthol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D039821:Monoterpenes; D010634:Phenobarbital / Q000494:pharmacology; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
chemical_list: D002250:Carbon Radioisotopes; D000081005:Cyclohexane Monoterpenes; D039821:Monoterpenes; D011506:Proteins; D008610:Menthol; C039648:pulegone; D008748:Methylcholanthrene; D010634:Phenobarbital