Porcine cytochrome P450 and metabolism

The pig and especially the minipig are becoming increasingly used as a test animal both in pharmacological and toxicological testing of new compounds. The minipig is used because of its size, it is easy to handle and less test substrate is required. When using an animal species for testing it is of importance to know if the test animal's posses the same abilities to metabolize drugs as humans. Some of the P450 enzymes have been characterized in the pig regarding substrate specificity, inhibition and regulation. The porcine enzymes CYP1A, CYP2A and CYP3A all metabolize the same test substrates as the human enzymes, whereas the enzymes CYP2B, CYP2D, and CYP2E in pig on the other hand seem to be different from the human enzymes concerning metabolism of the well know test substrates. Some of the porcine enzymes have been sequenced i.e. CYP1A, CYP2A, CYP2B, CYP2D, CYP2E and CYP3A and not surprisingly the porcine CYPs that metabolize the human test substrates are about 75% identical in cDNA sequences. What is needed is inhibitory antibodies against each of the porcine enzymes, in order to test whether a test compound is metabolized by one or the other enzyme. Until now chemical inhibitors have been used, but they are rarely 100% specific. Anti-human inhibitory antibodies have also been used, but they may not recognize the porcine enzyme and therefore will not inhibit the reaction. Antibodies for immunoblotting would also make it possible to estimate how much of the total P450 the individual enzymes comprise. From what is known about the porcine P450, it can be concluded that the pig seems to be a good test species if CYP1A, CYP2A or CYP3A are involved in the metabolism of the test compound, depending on the contribution of other enzymes in competing pathways.     

Inhibition of cytochrome P450 2E1 by propofol in human and porcine liver microsomes

While almost anesthetics are metabolized by the cytochrome P450 (CYP) 3A4, some major volatile ones such as halothane and sevoflurane are metabolized by CYP2E1 in humans. To determine whether 2,6-diisopropylphenol (propofol), a widely used intravenous anesthetic agent, known to inhibit CYP3A4 and CYP1A2, also inhibits CYP2E1, 6-OH hydroxylation of chlorzoxazone, a prototypical CYP2E1 substrate, was estimated using two pools of human microsomes and one pool of porcine microsomes from seven livers. Basal human enzyme activities were characterized by a V(max) of 1426+/-230 and 288+/-29 pmol min(-1)mg(-1) protein and a K(m) of 122+/-47 and 149+/-42 microM, while the corresponding porcine activities were associated with a V(max) of 352+/-42 pmol min(-1)mg(-1) protein and a K(m) of 167+/-38 microM. A competitive inhibition of CYP2E1 by propofol was observed with low inhibition constants in the therapeutic range in both porcine (19 microM) and human (48 microM) liver microsomes. These in vitro results suggest that propofol could have a protective effect on toxic metabolite activation of compounds catalyzed by CYP2E1.     

The role of CYP2A and CYP2E1 in the metabolism of 3-methylindole in primary cultured porcine hepatocytes.

The accumulation of 3-methylindole (3MI) in uncastrated male pigs (boars) is a major cause of boar taint, which negatively affects the quality of meat from the animal. Previously, CYP2E1 and CYP2A have been identified as cytochrome P450 (P450) isoforms involved in the metabolism of 3MI using porcine liver microsomes. This study further examines the role of these isoforms in the metabolism of 3MI using a primary porcine hepatocyte model by examining metabolic profiles of 3MI after incubation with P450 inhibitors. Incubation of hepatocytes with 4-methylpyrazole resulted in a selective inhibition of CYP2E1 activity as determined by p-nitrophenol hydroxylase activity and an associated significant decrease in the production of the 3MI metabolites 3-hydroxy-3-methyloxindole and 3-methyloxindole. Furthermore, inhibition of CYP2A, as assayed by coumarin 7-hydroxylase activity, using 8-methoxypsoralen and diethyldithiocarbamate was not associated with any further significant inhibition of the production of 3MI metabolites. Treatment with general P450 inhibitors resulted in further decreases in CYP2E1 activity and a more dramatic decrease in the production of 3MI metabolites, suggesting that additional P450s may be involved in the phase 1 metabolism of 3-methylindole. In conclusion, CYP2E1 activity levels are more important than CYP2A activity levels for the metabolism of 3-methylindole in isolated pig hepatocytes.     

In vivo effect of dried chicory root (Cichorium intybus L.) on xenobiotica metabolising cytochrome P450 enzymes in porcine liver

Cytochrome P450 (CYP) enzymes are widely studied for their involvement in metabolism of drugs and endogenous compounds. In porcine liver, CYP1A2, 2A and 2E1 are important for the metabolism of skatole. Feeding chicory roots to pigs is known to decrease the skatole concentration in plasma and fat. In the present study we investigated the effect of chicory on CYP mRNA and protein expression, as well as their activity. Male pigs were feed dried chicory root for 16 days before liver samples were collected. By the use of RT-PCR and Western blotting we showed that the mRNA and protein expression of CYP1A2 and 2A were increased in chicory fed pigs. The mRNA expression of CYP2E1 was increased, while there was no effect on protein expression. Activity of CYP1A2 and 2A were increased in chicory feed pigs; this was not the case for CYP2E1 activity. In conclusion; oral administration of chicory root for 16 days to pigs increased the mRNA expression of CYP1A2, 2A and 2E1; and the protein expression of CYP1A2 and 2A. The activities of CYP1A2 and 2A were increased.     

Effect of testicular steroids on catalytic activities of cytochrome P450 enzymes in porcine liver microsomes.

The testicular steroids androstenone (A), 17beta-oestradiol (E2) and testosterone (T) were tested for their ability to alter CYP2E1 and CYP2A activity in porcine liver microsomes from male and female pigs. This is the first in vitro study indicating that sex steroids have a potential to modify microsomal CYP2E1 activity, the main skatole-metabolising enzyme. A and E2 exerted an inhibitory effect on CYP2E1 mediated hydroxylation of p-nitrophenol to p-nitrocatechol although the mechanism of this inhibition differed for these steroids. The inhibitory effect of A on CYP2E1, as determined by kinetic analysis, might be due to the competitive binding of A and p-nitrophenol to the same site of CYP2E1. Including E2 into the incubations resulted in decreased activities of CYP2E1 in male microsomes through a mixed mode of inhibition. Including pre-incubation steps eliminated this inhibition in male microsomes, and resulted in increased CYP2E1 activities in the microsomes from female pigs. Testosterone was ineffective as an inhibitor of either CYP2E1 or CYP2A activities. Overall, our findings indicate that A and E2 have the potential to modify the catalytic activities of porcine CYP2E1 in vitro. However, the significance of this modification for skatole metabolism in vivo is questionable.     

Metabolism of 3-methylindole by porcine liver microsomes: responsible cytochrome P450 enzymes.

The role of different cytochrome P450 enzymes on the metabolism of 3-methylindole (3MI) was investigated using selective chemical inhibitors. Eight chemical inhibitors of P450 enzymes were screened for their inhibitory specificity towards 3MI metabolism in porcine microsomes: alpha-naphthoflavone (CYP1A1/2), 8-methoxypsoralen (CYP2A6), menthofuran (CYP2A6), diethyldithiocarbamate (CYP2A6), 4-methylpyrazole (CYP2E1), sulphaphenazole (CYP2C9), quinidine (CYP2D6), and troleandomycin (CYP3A4). The production of 3MI metabolites was only affected by the presence of inhibitors of CYP2A6 and CYP2E1 in the microsomal incubations. In a second experiment, a set of porcine microsomes (n = 30) was analyzed for CYP2A6 content by protein immunoblot analysis and for their coumarin 7-hydroxylation activity (CYP2A6 activity). Both CYP2A6 content and enzymatic activity were found to be highly and negatively correlated with 3MI fat content. The results of the present study indicate that the CYP2A6 porcine ortholog plays an important role in the metabolism of 3MI and that measurement of CYP2A6 levels and/or activity could be a useful marker for 3MI-induced boar taint.     

A repressive cross-regulation between catalytic and promoter activities of the CYP1A1 and CYP2E1 genes: role of H(2)O(2)

Cytochrome P450 enzymes catalyze the first step of the metabolism and subsequent elimination of hydrophobic xenobiotics. However, the activity of some isoforms, among them CYP1A1 and CYP2E1, may result in cellular insults such as oxidative stress and activation of procarcinogen compounds into reactive metabolites. The regulation of the expression of these enzymes is therefore important. We have previously shown that the CYP1A1 gene promoter was repressed by oxidative stress. We show here that the CYP2E1 gene promoter is down-regulated by exogenous H(2)O(2) addition and glutathione depletion. It is also repressed by the transfection of a CYP2E1 expression vector, which elicits an intracellular H(2)O(2) generation. This autoregulation is limited by catalase (which catalyzes the catabolism of H(2)O(2)), thus implying H(2)O(2) as a mediator of the negative feedback mechanism. Furthermore, we observed that the activity of CYP1A1 resulting either from the stimulation of the endogenous gene by benzo[a]pyrene treatment or from the transfection of an expression vector, repressed the activity of the CYP2E1 gene promoter. Conversely, CYP2E1 overexpression repressed the activity of the CYP1A1 gene promoter. In both cases, catalase and a specific inhibitor of one enzyme prevented the repression of the other. This suggests that the generation of H(2)O(2) during the catalytic cycle of these enzymes is a mediator of the cross-regulatory mechanisms. These novel repressive mechanisms of autoregulation and cross-regulation using H(2)O(2) as a common mediator may limit the potential toxicity resulting from high cytochrome P450 activity within the cell.     

细胞色素P450 CYP2E1酶构型特征及其表达调控机制的研究进展

细胞色素P450CYP2E1酶参与代谢活化及失活多种前毒物、前致癌物和少数药物。在细胞色素P450超家族中,CYP2E1具有易介导自由基生成引发氧化应激反应的特征。CYP2E1表达水平可能是机体对环境和工业毒物或致癌物敏感程度的重要因素。研究表明,CYP2E1可被多种内、外源性物质所调控,并且CYP2E1的药理和毒理学功能与其以蛋白构型为基础的代谢行为密切相关。本文综述了CYP2E1基因多态性、酶构型特征与其代谢活性间的关系,并分析了其区别于其他细胞色素P450亚型的表达调控机制。     

Evaluation of methoxsalen, tranylcypromine, and tryptamine as specific and selective CYP2A6 inhibitors in vitro.

CYP2A6 is the principle enzyme metabolizing nicotine to its inactive metabolite cotinine. In this study, the selective probe reactions for each major cytochrome P450 (P450) were used to evaluate the specificity and selectivity of the CYP2A6 inhibitors methoxsalen, tranylcypromine, and tryptamine in cDNA-expressing and human liver microsomes. Phenacetin O-deethylation (CYP1A2), coumarin 7-hydroxylation (CYP2A6), diclofenac 4'-hydroxylation (CYP2C9), omeprazole 5-hydroxylation (CYP2C19), dextromethorphan O-demethylation (CYP2D6), 7-ethoxy-4-trifluoromethylcoumarin deethylation (CYP2B6), p-nitrophenol hydroxylation (CYP2E1), and omeprazole sulfonation (CYP3A4) were used as index reactions. Apparent K(i) values for inhibition of P450s' (1A2, 2A6, 2B6, 2C9, 2C19, 2D6, 2E1, and 3A4) activities showed that tranylcypromine, methoxsalen, and tryptamine have high specificity and relative selectivity for CYP2A6. In cDNA-expressing microsomes, tranylcypromine inhibited CYP2A6 (K(i) = 0.08 microM) with about 60- to 5000-fold greater potency relative to other P450s. Methoxsalen inhibited CYP2A6 (K(i) = 0.8 microM) with about 3.5- 94-fold greater potency than other P450s, except for CYP1A2 (K(i) = 0.2 microM). Tryptamine inhibited CYP2A6 (K(i) = 1.7 microM) with about 6.5- 213-fold greater potency relative to other P450s, except for CYP1A2 (K(i) = 1.7 microM). Similar results were also obtained with methoxsalen and tranylcypromine in human liver microsomes. R-(+)-Tranylcypromine, (+/-)-tranylcypromine, and S-(-)-tranylcypromine competitively inhibited CYP2A6-mediated metabolism of nicotine with apparent K(i) values of 0.05, 0.08, and 2.0 microM, respectively. Tranylcypromine [particularly R-(+) isomer], tryptamine, and methoxsalen are specific and relatively selective for CYP2A6 and may be useful in vivo to decrease smoking by inhibiting nicotine metabolism with a low risk of metabolic drug interactions.     

CYP2B6 and CYP2C19 as the major enzymes responsible for the metabolism of selegiline, a drug used in the treatment of Parkinson's disease, as revealed from experiments with recombinant enzymes.

In view of conflicting data in the literature regarding the enzyme(s) responsible for metabolism of selegiline, a drug used in the treatment of Parkinson's disease, investigations were carried out in vitro using the human cytochrome P450 enzymes CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 recombinantly expressed in yeast to elucidate the enzyme specificity in selegiline metabolism. In the yeast microsomes used, desmethylselegiline and levomethamphetamine were formed from selegiline at significant rates. The highest contribution to the hepatic clearance of selegiline was calculated to be exerted by CYP2B6 (124 l/h) CYP2C19 (82 l/h), whereas CYP3A4 (27 l/h) and CYP1A2 (21 l/h) were of less importance. Antibodies against CYP2B6 inhibited metabolism of selegiline in microsomes containing CYP2B6 but not in microsomes without significant amounts of the enzyme. In contrast to previous reports, we could not find any role for CYP2D6 in the metabolism of selegiline. The data strongly indicate that the high extent of interindividual variation seen in vivo for selegiline clearance is caused by the metabolism of the compound by the highly polymorphic CYP2B6 and CYP2C19.     

Inhibition of the human liver microsomal and human cytochrome P450 1A2 and 3A4 metabolism of estradiol by deployment-related and other chemicals.

Cytochromes P450 (P450s) are major catalysts in the metabolism of xenobiotics and endogenous substrates such as estradiol (E2). It has previously been shown that E2 is predominantly metabolized in humans by CYP1A2 and CYP3A4 with 2-hydroxyestradiol (2-OHE2) the major metabolite. This study examines effects of deployment-related and other chemicals on E2 metabolism by human liver microsomes (HLM) and individual P450 isoforms. Kinetic studies using HLM, CYP3A4, and CYP1A2 showed similar affinities (Km) for E2 with respect to 2-OHE2 production. Vmax and CLint values for HLM are 0.32 nmol/min/mg protein and 7.5 microl/min/mg protein; those for CYP3A4 are 6.9 nmol/min/nmol P450 and 291 microl/min/nmol P450; and those for CYP1A2 are 17.4 nmol/min/nmol P450 and 633 microl/min/nmol P450. Phenotyped HLM use showed that individuals with high levels of CYP1A2 and CYP3A4 have the greatest potential to metabolize E2. Preincubation of HLM with a variety of chemicals, including those used in military deployments, resulted in varying levels of inhibition of E2 metabolism. The greatest inhibition was observed with organophosphorus compounds, including chlorpyrifos and fonofos, with up to 80% inhibition for 2-OHE2 production. Carbaryl, a carbamate pesticide, and naphthalene, a jet fuel component, inhibited ca. 40% of E2 metabolism. Preincubation of CYP1A2 with chlorpyrifos, fonofos, carbaryl, or naphthalene resulted in 96, 59, 84, and 87% inhibition of E2 metabolism, respectively. Preincubation of CYP3A4 with chlorpyrifos, fonofos, deltamethrin, or permethrin resulted in 94, 87, 58, and 37% inhibition of E2 metabolism. Chlorpyrifos inhibition of E2 metabolism is shown to be irreversible.     

Cytochrome P-450 3A4 and 2C8 are involved in zopiclone metabolism.

Zopiclone is a widely prescribed, nonbenzodiazepine hypnotic that is extensively metabolized by the liver in humans. The aim of the present study was to identify the human cytochrome P-450 (CYP) isoforms involved in zopiclone metabolism in vitro. Zopiclone metabolism was studied with different human liver microsomes and a panel of heterologously expressed human CYPs (CYP1A2, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, and 3A4). In human liver microsomes, zopiclone was metabolized into N-desmethyl-zopiclone (ND-Z) and N-oxide-zopiclone (NO-Z) with the following K(m) and V(m) of 78 +/- 5 and 84 +/- 19 microM, 45 +/- 1 and 54 +/- 5 pmol/min/mg for ND-Z and NO-Z generation, respectively. Ketoconazole (CYP3A inhibitor) inhibited approximately 40% of the generation of both metabolites, sulfaphenazole (CYP2C inhibitor) inhibited the formation of ND-Z, whereas alpha-naphtoflavone (CYP1A), quinidine (CYP2D6), and chlorzoxazone (CYP2E1) did not affect zopiclone metabolism. The generation of ND-Z and NO-Z were highly correlated to testosterone 6beta-hydroxylation (CYP3A activity, r = 0.95 and 0.92, respectively; p =.0001), and ND-Z was highly correlated to CYP2C8 activity (paclitaxel 6alpha-hydroxylase; r = 0.76, p =.004). Recombinant CYP2C8 had the highest enzymatic activity toward zopiclone metabolism into both its metabolites, followed by CYP2C9 and 3A4. CYP3A4 is the major enzyme involved in zopiclone metabolism in vitro, and CYP2C8 contributes significantly to ND-Z formation.     

Lack of single-dose disulfiram effects on cytochrome P-450 2C9, 2C19, 2D6, and 3A4 activities: evidence for specificity toward P-450 2E1.

Disulfiram and its primary metabolite diethyldithiocarbamate are effective mechanism-based inhibitors of cytochrome P-450 2E1 (CYP2E1)1 in vitro. Single-dose disulfiram diminishes CYP2E1 activity in vivo and has been used to identify CYP2E1 participation in human drug metabolism and prevent CYP2E1-mediated toxification. Specificity of single-dose disulfiram toward CYP2E1 in vivo, however, remains unknown. This investigation determined single-dose disulfiram effects on human CYP 2C9, 2C19, 2D6, and 3A4 activities in vivo. In four randomized crossover experiments, volunteers received isoform-selective probes (oral tolbutamide, mephenytoin, dextromethorphan, or i.v. midazolam) on two occasions, 10 h after oral disulfiram or after no pretreatment (controls). Plasma and/or urine parent and/or metabolite concentrations were measured by HPLC or gas chromatography-mass spectrometry. CYP2C9, 2C19, 2D6, and 3A4 activities were determined from the tolbutamide metabolic ratio, 4'-hydroxymephenytoin excretion, and dextromethorphan/dextrorphan ratios in urine and midazolam systemic clearance, respectively. Midazolam clearance (670 +/- 190 versus 700 +/- 240 ml/min, disulfiram versus controls), dextromethorphan/dextrorphan metabolic ratio (0.013 +/- 0.033 versus 0.015 +/- 0.035), 4'-hydroxymephenytoin excretion (122 +/- 22 versus 128 +/- 25 micromol), and tolbutamide metabolite excretion (577 +/- 157 versus 610 +/- 208 micromol) were not significantly altered by disulfiram pretreatment, although the tolbutamide metabolic ratio was slightly diminished after disulfiram (60 +/- 17 versus 81 +/- 40, p <.05). Results show that single-dose disulfiram does not cause clinically significant inhibition of human CYP2C9, 2C19, 2D6, and 3A4 activities in vivo. When single-dose disulfiram is used as an in vivo probe for P-450, inhibition of drug metabolism suggests selective involvement of CYP2E1. Single-dose disulfiram should not cause untoward drug interactions from inhibition of other P-450 isoforms.     

Frequency distribution of high risk alleles of CYP2C19, CYP2E1, CYP3A4 genes in Haryana population

The genotype of an individual can significantly influence the disposition of a chemical, and determine their susceptibility to its toxicity. Many enzymes involved in either activation or detoxification of chemical carcinogen metabolism are polymorphically expressed, with the alleles presenting different enzymatic activities and some of them having been associated with susceptibility to cancer. Cytochrome P450 (P450 or CYP) constitutes the most important phase I enzyme group responsible for the metabolism of endogenous and exogenous (xenobiotics) substances. The present study was aimed to analyze the frequencies of commonly known polymorphisms of human xenobiotic metabolizing genes (XMG) in the Haryana State population of North India. The study was conducted in 308 healthy Haryana volunteers. DNA was extracted from leucocytes and the genetic polymorphisms in CYP2C19*2, CYP2C19*3, CYP2E1*5B and CYP3A4*1B were determined by digesting the PCR Product with restriction enzymes BamHI, SmaI, PstI and PstI respectively. The genotype frequencies of CYP2C19*2, CYP2C19*3, CYP2E1*5B, and CYP3A4*1B were found to be 22.0%, 0.0%, 2.11% and 2.0% respectively. The North Indian population which is known to be Caucasoid Aryans is ethnically different from South Indians known as Caucasoid Dravidians but no significant difference in genetic polymorphism was found.     

The human hepatic metabolism of simvastatin hydroxy acid is mediated primarily by CYP3A,and not CYP2D6

AIMS: To identify the cytochrome P450 (CYP) isoforms responsible for the metabolism of simvastatin hydroxy acid (SVA), the most potent metabolite of simvastatin (SV). METHODS: The metabolism of SVA was characterized in vitro using human liver microsomes and recombinant CYPs. The effects of selective chemical inhibitors and CYP antibodies on SVA metabolism were assessed in human liver microsomes. RESULTS: In human liver microsomes, SVA underwent oxidative metabolism to three major oxidative products, with values for Km and Vmax ranging from about 50 to 80 microM and 0.6 to 1.9 nmol x min(-1) x mg(-1) protein, respectively. Recombinant CYP3A4, CYP3A5 and CYP2C8 all catalysed the formation of the three SVA metabolites, but CYP3A4 was the most active. CYP2D6 as well as CYP2C19, CYP2C9, CYP2A6, CYP1A2 did not metabolize SVA. Whereas inhibitors that are selective for CYP2D6, CYP2C9 or CYP1A2 did not significantly inhibit the oxidative metabolism of SVA, the CYP3A4/5 inhibitor troleandomycin markedly (about 90%) inhibited SVA metabolism. Quercetin, a known inhibitor of CYP2C8, inhibited the microsomal formation of SVA metabolites by about 25-30%. Immunoinhibition studies revealed 80-95% inhibition by anti-CYP3A antibody, less than 20% inhibition by anti-CYP2C19 antibody, which cross-reacted with CYP2C8 and CYP2C9, and no inhibition by anti-CYP2D6 antibody. CONCLUSIONS: The metabolism of SVA in human liver microsomes is catalysed primarily (> or = 80%) by CYP3A4/5, with a minor contribution (< or = 20%) from CYP2C8. CYP2D6 and other major CYP isoforms are not involved in the hepatic metabolism of SVA.     

Advances in the interpretation and prediction of CYP2E1 metabolism from a biochemical perspective

BACKGROUND: Cytochrome P450 2E1 (CYP2E1) plays a central role in the metabolism and metabolic activation of a large number of small, mostly xenobiotic compounds. These qualities distinguish CYP2E1 from traditional enzymes and pose significant challenges to understanding the role and consequences of CYP2E1-mediated metabolism. OBJECTIVE: This review discusses recent advances in kinetic profiling, quantitative structure-activity relationships and structural studies that have furthered the development of tools to interpret and predict CYP2E1 metabolism. METHODS: Analysis of kinetic profiles by specific mechanisms produces important parameters describing specificity, stoichiometry and metabolism of molecules. Quantitative structure-activity relationships reveal a more specific basis for molecular recognition by CYP2E1. The corresponding protein structures imparting these interactions are the focus of chemical modifications, site-directed mutagenesis and homology modeling studies. RESULTS: Compilation of kinetic profiling for CYP2E1 substrates established the selectivity for small substrates, whose characteristics could be generalized in parameters for hydrophobicity and steric properties as determined by quantitative structure-activity relationships. The possibility of an effector site for monocyclic compounds added an interesting variable to these modeling efforts. Various structural studies identified important residues contributing to binding and catalysis as well as the volume and location of the active site relative to the heme moiety. Pressure and carbon monoxide-binding experiments also demonstrated the inherent conformational flexibility of CYP2E1 that may contribute to rate-limiting steps during catalytic turnover. CONCLUSION: Although combinations of these approaches have reinforced important observations, more work is needed to verify findings and seek broader impacts for various interpretative and predictive tools.     

Effect of conjugated equine estrogens on oxidative metabolism in middle-aged and elderly postmenopausal women

The effects of conjugated equine estrogens (CEE) 0.625 mg daily on cytochrome P450 (CYP) were quantified in 12 middle-aged and 13 elderly postmenopausal women at baseline and 6 months later. CYP phenotype was characterized by caffeine (CYP1A2), chlorzoxazone (CYP2E1), dapsone (CYP, N-acetyltransferase 2), dextromethorphan (CYP2D6), and mephenytoin (CYP2C19) metabolism. CEE significantly decreased CYP1A2 (caffeine metabolic ratio: 0.57 +/- 0.20 before, 0.40 +/- 0.20 after, P = .001) and significantly increased CYP2D6 (dextromethorphan/dextrorphan ratio: 0.0116 +/- 0.0143 before, 0.0084 +/- 0.0135 after, P = .022) metabolism. CEE had no overall effect on CYP2C19, CYP2E1, CYP-mediated dapsone metabolism, and N-acetyltransferase 2. The dextromethorphan metabolic ratio decreased only in the seniors. The dapsone recovery ratio decreased in the middle-aged group and increased in the seniors. CEE significantly influenced CYP1A2, CYP2D6, and CYP-mediated dapsone oxidative metabolism but not CYP2C19, CYP2E1, or N-acetyltransferase 2 metabolism in postmenopausal women. Age influenced CYP2D6 metabolism and dapsone hydroxylation.