RT Journal Article
SR Electronic
T1 Quaternary Ammonium-Linked Glucuronidation of 1-Substituted Imidazoles by Liver Microsomes: Interspecies Differences and Structure-Metabolism Relationships
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1070
OP 1076
DO 10.1124/dmd.30.10.1070
VO 30
IS 10
A1 Vashishtha, Sarvesh C.
A1 Hawes, Edward M.
A1 McCann, Denis J.
A1 Ghosheh, Omar
A1 Hogg, Lawrence
YR 2002
UL http://dmd.aspetjournals.org/content/30/10/1070.abstract
AB N-Glucuronidation at an aromatic tertiary amine of 5-membered polyaza ring systems was investigated for a model series of eight 1-substituted imidazoles in liver microsomes from five species. The major objectives were to investigate substrate specificities of the series in human microsomes and interspecies variation for the prototype molecule, 1-phenylimidazole. The formed quaternary ammonium-linked metabolites were characterized by positive ion electrospray mass spectrometry. The incubation conditions for theN-glucuronidation of 1-substituted imidazoles were optimized; where for membrane disrupting agents, alamethicin was more effective than the detergents examined. The need to optimize alamethicin concentration was indicated by 4-fold interspecies variation in optimal concentration and by a change in effect from removal of glucuronidation latency to inhibition on increasing concentration. For the four species with quantifiableN-glucuronidation of 1-phenylimidazole, there were 8- and 18-fold variations in the determined apparentKm (range, 0.63 to 4.8 mM) andVmax (range, 0.08 to 1.4 nmol/min/mg of protein) values, respectively. The apparent clearance values (Vmax/Km) were in the following order: human ≅ guinea pig ≅ rabbit > rat ≅ dog (no metabolite detected). Monophasic kinetics were observed for theN-glucuronidation of seven substrates by human liver microsomes, which suggests that one enzyme is involved in each metabolic catalysis. No N-glucuronidation was observed for the substrate containing the para-phenyl substituent with the largest electron withdrawing effect, 1-(4-nitrophenyl)imidazole. Linear correlation analyses between apparent microsomal kinetics and substrate physicochemical parameters revealed significant correlations between Kmand lipophilicity (πpara or log P values) and betweenVmax/Km and both electronic properties (ςpara value) and pKa. The American Society for Pharmacology and Experimental Therapeutics