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[O-methyl 14C]naproxen O-demethylase activity in human liver microsomes: evidence for the involvement of cytochrome P4501A2 and P4502C9/10.
Drug Metab Dispos 1996; 24(1):126-36DM

Abstract

Cytochrome P450 (CYP) activity in human liver microsomes was measured after the O-demethylation of [O-methyl 14C]naproxen (NAPase). The formation of [14C]formaldehyde in the presence of microsomes was described by an apparent KM(1) and Vmax(1) of 0.16 +/- 0.09 mM and 4.1 +/- 2.8 nmol HCHO/min/mg protein (mean +/- SD; N = 5 different livers), respectively, over a relatively wide naproxen concentration (5-1600 microM) range. With two sets of microsomes, a high KM NAPase component was also detected (mean KM2 = 2.7 mM; mean Vmax2 = 23 nmol HCHO/min/mg). As expected, the O-demethylation of naproxen (0.4 mM) was found to be highly correlated with tolbutamide hydroxylase (TOLase) activity in a panel of human liver microsomes (r = 0.82, p < 0.01, N = 10) and was inhibited (32-54%) by a number of purported CYP2C (CYP2C9/10) inhibitors/substrates (e.g. phenytoin, sulfaphenazole, tienilic acid, tolbutamide, and ibuprofen). Only marginal decreases in activity (< or = 14%) were observed with inhibitors of other CYP proteins. However, NAPase activity was also found to correlate significantly with CYP1A2 [ethoxyresorufin O-deethylase (ERODase)] activity (r = 0.68, p < 0.05, n = 11). In addition, the reaction was inhibited (36-75%, N = 11 different livers) by furafylline (FURA), a CYP1A2-selective mechanism-based inhibitor. The effect of FURA and tienilic acid was additive, leading to 90 +/- 4.2% inhibition of NAPase activity. FURA-inhibited activity also significantly correlated with ERODase activity (r = 0.78, p < 0.01, N = 11), whereas tienilic acid-inhibited activity correlated with TOLase activity (r = 0.63, p < 0.05, N = 10). In human B-lymphoblast microsomes, cDNA-expressed CYP1A2 exhibited relatively high activity (KM = 0.25 mM; Vmax = 24 nmol/min/nmol CYP), when compared with CYP2A6, CYP2D6, CYP2E1, CYP2B6, and CYP3A4. The kinetic parameters for reconstituted purified human liver microsomal CYP2C9 (KM = 0.43 mM; Vmax = 11 nmol/min/nmol CYP) were comparable with those of CYP1A2. It is concluded that the O-demethylation of naproxen (< or = 0.4 mM) is catalyzed by CYP2C subfamily members (CYP2C9/10) and CYP1A2 in human liver microsomes.

Authors+Show Affiliations

Drug Metabolism Department, Abbott Laboratories, Abbott Park, IL 60064, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

8825200

Citation

Rodrigues, A D., et al. "[O-methyl 14C]naproxen O-demethylase Activity in Human Liver Microsomes: Evidence for the Involvement of Cytochrome P4501A2 and P4502C9/10." Drug Metabolism and Disposition: the Biological Fate of Chemicals, vol. 24, no. 1, 1996, pp. 126-36.
Rodrigues AD, Kukulka MJ, Roberts EM, et al. [O-methyl 14C]naproxen O-demethylase activity in human liver microsomes: evidence for the involvement of cytochrome P4501A2 and P4502C9/10. Drug Metab Dispos. 1996;24(1):126-36.
Rodrigues, A. D., Kukulka, M. J., Roberts, E. M., Ouellet, D., & Rodgers, T. R. (1996). [O-methyl 14C]naproxen O-demethylase activity in human liver microsomes: evidence for the involvement of cytochrome P4501A2 and P4502C9/10. Drug Metabolism and Disposition: the Biological Fate of Chemicals, 24(1), pp. 126-36.
Rodrigues AD, et al. [O-methyl 14C]naproxen O-demethylase Activity in Human Liver Microsomes: Evidence for the Involvement of Cytochrome P4501A2 and P4502C9/10. Drug Metab Dispos. 1996;24(1):126-36. PubMed PMID: 8825200.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - [O-methyl 14C]naproxen O-demethylase activity in human liver microsomes: evidence for the involvement of cytochrome P4501A2 and P4502C9/10. AU - Rodrigues,A D, AU - Kukulka,M J, AU - Roberts,E M, AU - Ouellet,D, AU - Rodgers,T R, PY - 1996/1/1/pubmed PY - 1996/1/1/medline PY - 1996/1/1/entrez SP - 126 EP - 36 JF - Drug metabolism and disposition: the biological fate of chemicals JO - Drug Metab. Dispos. VL - 24 IS - 1 N2 - Cytochrome P450 (CYP) activity in human liver microsomes was measured after the O-demethylation of [O-methyl 14C]naproxen (NAPase). The formation of [14C]formaldehyde in the presence of microsomes was described by an apparent KM(1) and Vmax(1) of 0.16 +/- 0.09 mM and 4.1 +/- 2.8 nmol HCHO/min/mg protein (mean +/- SD; N = 5 different livers), respectively, over a relatively wide naproxen concentration (5-1600 microM) range. With two sets of microsomes, a high KM NAPase component was also detected (mean KM2 = 2.7 mM; mean Vmax2 = 23 nmol HCHO/min/mg). As expected, the O-demethylation of naproxen (0.4 mM) was found to be highly correlated with tolbutamide hydroxylase (TOLase) activity in a panel of human liver microsomes (r = 0.82, p < 0.01, N = 10) and was inhibited (32-54%) by a number of purported CYP2C (CYP2C9/10) inhibitors/substrates (e.g. phenytoin, sulfaphenazole, tienilic acid, tolbutamide, and ibuprofen). Only marginal decreases in activity (< or = 14%) were observed with inhibitors of other CYP proteins. However, NAPase activity was also found to correlate significantly with CYP1A2 [ethoxyresorufin O-deethylase (ERODase)] activity (r = 0.68, p < 0.05, n = 11). In addition, the reaction was inhibited (36-75%, N = 11 different livers) by furafylline (FURA), a CYP1A2-selective mechanism-based inhibitor. The effect of FURA and tienilic acid was additive, leading to 90 +/- 4.2% inhibition of NAPase activity. FURA-inhibited activity also significantly correlated with ERODase activity (r = 0.78, p < 0.01, N = 11), whereas tienilic acid-inhibited activity correlated with TOLase activity (r = 0.63, p < 0.05, N = 10). In human B-lymphoblast microsomes, cDNA-expressed CYP1A2 exhibited relatively high activity (KM = 0.25 mM; Vmax = 24 nmol/min/nmol CYP), when compared with CYP2A6, CYP2D6, CYP2E1, CYP2B6, and CYP3A4. The kinetic parameters for reconstituted purified human liver microsomal CYP2C9 (KM = 0.43 mM; Vmax = 11 nmol/min/nmol CYP) were comparable with those of CYP1A2. It is concluded that the O-demethylation of naproxen (< or = 0.4 mM) is catalyzed by CYP2C subfamily members (CYP2C9/10) and CYP1A2 in human liver microsomes. SN - 0090-9556 UR - https://www.unboundmedicine.com/medline/citation/8825200/[O_methyl_14C]naproxen_O_demethylase_activity_in_human_liver_microsomes:_evidence_for_the_involvement_of_cytochrome_P4501A2_and_P4502C9/10_ L2 - http://dmd.aspetjournals.org/cgi/pmidlookup?view=long&amp;pmid=8825200 DB - PRIME DP - Unbound Medicine ER -