title: Species difference in stereoselective involvement of CYP3A in the mono-N-dealkylation of disopyramide.
abstract: 1. To determine which CYP isoenzyme is involved in the N-dealkylation of disopyramide (DP) metabolism in human and dog, and to determine the stereoselectivity of DP metabolism with human CYP and dog CYP isoenzymes, the following in vitro metabolism studies of DP were conducted: correlation between human CYP isoenzyme activities and DP metabolism with human liver microsomes; inhibition of DP metabolism in human and dog liver microsomes with chemical inhibitors of CYP isoenzymes; inhibition of DP metabolism in human microsomes with human CYP antibodies; inhibition of DP metabolism in dog liver microsomes with human and dog CYP antibodies; metabolism of DP with human (CYP3A4) and dog (CYP3A12) cDNA-expressed isoenzymes; determination of Km and Vmax of DP enantiomers by using cDNA-expressed CYP3A4 and CYP3A12. 2. In human liver microsomes, the formation of the mono-N-dealkylated disopyramide (MNDP) metabolite was best correlated with CYP3A4 activities. DP metabolism was substantially inhibited by ketoconazole, troleandomycin (TA) and human CYP3A4 antibody. DP was metabolized by cDNA-expressed CYP3A isoenzymes. In dog liver microsomes, DP metabolism was inhibited by ketoconazole, TA and dog anti-CYP3A12. DP was also metabolized by cDNA-expressed CYP3A12. 3. CYP3A4 and CYP3A12 are the principal isoenzymes involved in DP metabolism in human and dog respectively. There was no stereoselectivity in N-dealkylation of DP by human CYP3A4. However, there was notable stereoselectivity in the N-dealkylation by dog CYP3A12.
authors.affiliation: Metabolism and Safety Evaluation, Pharmacia, Skokie, IL 60077, USA.
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: J F
authors.initials: JF
authors.lastname: Fitzloff
authors.forename: L C
authors.initials: LC
authors.lastname: Engel
authors.forename: C S
authors.initials: CS
authors.lastname: Cook
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001189:Aryl Hydrocarbon Hydroxylases; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004206:Disopyramide / Q000378:metabolism*; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008658:Inactivation, Metabolic; D007654:Ketoconazole / Q000494:pharmacology; D007700:Kinetics; D008862:Microsomes, Liver / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010089:Oxidoreductases, N-Demethylating / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D014217:Troleandomycin / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C475779:cytochrome P-450 CYP3A12 (canine); C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating; D004206:Disopyramide; D007654:Ketoconazole