title: Induction of the rat hepatic microsomal mixed-function oxidases by 3 imidazole-containing antifungal agents: selectivity for the cytochrome P-450IIB and P-450III families of cytochromes P-450.
abstract: Administration of the imidazole antifungal agents ketoconazole, miconazole and clotrimazole gave rise to increases in the microsomal cytochrome P-450 levels and the NADPH-dependent reduction of cytochrome c. Clotrimazole, and to a much lesser extent miconazole and ketoconazole, stimulated the dealkylation of pentoxyresorufin. All 3 agents gave rise to small, but significant increases in the O-deethylation of ethoxycoumarin and ethoxyresorufin. The antifungal-induced O-deethylation of ethoxycoumarin was much more sensitive to inhibition by metyrapone rather than by alpha-naphthoflavone. The binding of metyrapone to reduced microsomes was enhanced by treatment of animals with the 3 antifungal agents, clotrimazole being clearly the most potent. Immunoquantitation of cytochrome P-450 proteins using an ELISA procedure and employing anti-cytochrome P-450c (P-450IA1, P-448 low spin) and P-450b (P-450IIB1) antisera revealed that clotrimazole and miconazole, but not ketoconazole, induced the levels of phenobarbital-induced cytochromes P-450, while none of the antifungal agents increased the levels of cytochrome of P-448 proteins. Similar results were obtained using Western blots employing the above antibodies. On SDS-polyacrylamide gel electrophoresis microsomes derived from animals pretreated with clotrimazole showed intensification of a band at 51 kDa which was identified by Western blotting as the PCN-inducible form of cytochrome P-450 (cytochrome P-450p, P-450III family). Similar, but less pronounced intensification was seen with microsomes from animals pretreated with miconazole and ketoconazole. Furthermore, microsomes from clotrimazole- and ketoconazole-treated animals interacted with erythromycin to yield type I spectra. It is concluded that the imidazole-containing agents clotrimazole and miconazole, and to a much lesser extent ketoconazole, are potent inducers of the rat hepatic microsomal mixed-function oxidases, displaying selectivity towards the P-450IIB (phenobarbital-inducible) and P-450III (PCN-inducible) families of cytochrome P-450 proteins.
authors.affiliation: Department of Biochemistry, University of Surrey, Guildford, U.K.
authors.forename: A D
authors.initials: AD
authors.lastname: Rodrigues
authors.forename: P R
authors.initials: PR
authors.lastname: Waddell
authors.forename: E
authors.initials: E
authors.lastname: Ah-Sing
authors.forename: B A
authors.initials: BA
authors.lastname: Morris
authors.forename: C R
authors.initials: CR
authors.lastname: Wolf
authors.forename: C
authors.initials: C
authors.lastname: Ioannides
mesh_terms: D000818:Animals; D003022:Clotrimazole / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D003640:Dealkylation; D004790:Enzyme Induction; D004917:Erythromycin / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology*; D007654:Ketoconazole / Q000494:pharmacology*; D008297:Male; D008825:Miconazole / Q000494:pharmacology*; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D007093:Imidazoles; D004917:Erythromycin; D008825:Miconazole; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D003022:Clotrimazole; D007654:Ketoconazole