Induction and inhibition of cytochrome P-450-dependent monooxygenases in hamster tissues by ethanol

Effects of Shengmai San on key enzymes involved in hepatic and intestinal drug metabolism in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Shengmai San (SMS) has been commonly used as a traditional Chinese medicine for the treatment of cardiovascular disorders, of which drug interactions need to be assessed for the safety concern. There is little evidence for the alterations of hepatic and intestinal drug-metabolizing enzymes after repeated SMS treatments to assess drug interactions.

AIM OF THE STUDY

The studies aim to illustrate the effects of repeated treatments with SMS on cytochrome P450s (CYPs), reduced nicotinamide adenine dinucleotide (phosphate)-quinone oxidoreductase (NQO), uridine diphosphate-glucuronosyltransferase (UGT), and glutathione S-transferase (GST) using in vivo rat model.

MATERIALS AND METHODS

The SMS was prepared using Schisandrae Fructus, Ginseng Radix, and Ophiopogonis Radix (OR) (1:2:2). Chromatographic analyses of decoctions were performed using ultra-performance liquid chromatography (UPLC) and LC-mass spectrometry. Sprague-Dawley rats were orally treated with the SMS and its component herbal decoctions for 2 or 3 weeks. Hepatic and intestinal enzyme activities were determined. CYP3A expression and the kinetics of intestinal nifedipine oxidation (NFO, a CYP3A marker reaction) were determined.

RESULTS

Schisandrol A, schisandrin B, ginsenoside Rb1 and ophiopogonin D were identified in SMS. SMS selectively suppressed intestinal, but not hepatic, NFO activity in a dose- and time-dependent manner. Hepatic and intestinal UGT, NQO and GST activities were not affected. A 3-week SMS treatment decreased the maximal velocity of intestinal NFO by 50%, while the CYP3A protein level remained unchanged. Among SMS component herbs, the decoction of OR decreased intestinal NFO activity.

CONCLUSIONS

These findings demonstrate that 3-week treatment with SMS and OR suppress intestinal, but not hepatic CYP3A function. It suggested that the potential interactions of SMS with CYP 3A drug substrates should be noticed, especially the drugs whose bioavailability depends heavily on intestinal CYP3A.

Regulation of cytochrome P450 gene expression by ketamine: a review

INTRODUCTION

Although used as an anesthetic drug for decades, ketamine appears to have garnered renewed interest due to its potential therapeutic uses in pain therapy, neurology, and psychiatry. Ketamine undergoes extensive oxidative metabolism by cytochrome P450 (CYP) enzymes. Considerable efforts have been expended to elucidate the ketamine-induced regulation of CYP gene expression. The safety profile of chronic ketamine administration is still unclear. Understanding how ketamine regulates CYP gene expression is clinically meaningful. Areas covered: In this article, the authors provide a brief review of clinical applications of ketamine and its metabolism by CYP enzymes. We discuss the effects of ketamine on the regulation of CYP gene expression, exploring aspects of cytoskeletal remodeling, mitochondrial functions, and calcium homeostasis. Expert opinion: Ketamine may inhibit CYP gene expression through inhibiting calcium signaling, decreasing ATP levels, producing excessive reactive oxygen species, and subsequently perturbing cytoskeletal dynamics. Further research is still needed to avoid possible ketamine-drug interactions during long-term use in the clinic.

Metabolism and metabolomics of ketamine: a toxicological approach

Ketamine is a phencyclidine derivative and a non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptor for which glutamate is the full agonist. It produces a functional dissociation between the thalamocortical and limbic systems, a state that has been termed as dissociative anaesthesia. Considerable variability in the pharmacokinetics and pharmacodynamics between individuals that can affect dose-response and toxicological profile has been reported. This review aims to discuss pharmacokinetics of ketamine, namely focusing on all major and minor, active and inactive metabolites. Both ketamine optical isomers undergo hepatic biotransformation through the cytochrome P450, specially involving the isoenzymes 3A4 and 2B6. It is first N-demethylated to active metabolite norketamine. Different minor pathways have been described, namely hydroxylation of the cyclohexanone ring of ketamine and norketamine, and further conjugation with glucuronic acid to increase renal excretion. More recently, metabolomics data evidenced the alteration of several biological pathways after ketamine administration such as glycolysis, tricarboxylic acid cycle, amino acids metabolism and mitochondrial β-oxidation of fatty acids. It is expected that knowing the metabolism and metabolomics of ketamine may provide further insights aiming to better characterize ketamine from a clinical and forensic perspective.

Induction of rat hepatic cytochrome P-450 by ketamine and its toxicological implications

Ketamine is a common intravenous anesthetic and a frequent drug of abuse, alone or in combination with cocaine. However, the pharmacokinetic effects of ketamine have not been fully investigated. This study determined the effects of ketamine on cytochrome P-450 (P-450)-dependent catalytic activities, protein levels, and hepatotoxicity using male Wistar rats treated with 10, 20, 40, or 80 mg/kg ketamine intraperitoneally twice daily for 4 d. Treatment with ketamine produced a dose-dependent increase of pentoxyresorufin O-dealkylation activity of liver microsomes. Treatment with 80 mg/kg ketamine resulted in 14-, 3-, and 2-fold rise in O-dealkylation of pentoxyresorufin, ethoxyresorufin, and methoxyresorufin of rat liver microsomes, respectively. The treatment produced 31% and 86% increases in 7-ethoxycoumarin O-deethylation and erythromycin N-demethylation, respectively. In addition, aniline hydroxylation activity was elevated by 62%. Protein blot analysis of liver microsomal proteins revealed that 80 mg/kg ketamine induced P-450 1A, 2B, 2E1, and 3A proteins by 2-, 13-, 2-, and 2-fold, respectively. In reversibility study, ketamine-induced pentoxyresorufin O-dealkylation, 7-ethoxycoumarin O-deethylation, erythromycin N-demethylation, and methoxyresorufin O-demethylation activities of liver microsomes prepared from rats 4 d after ketamine treatment were 75%, 48%, 29%, and 38% lower than the respective activities of liver microsomes prepared from rats 1 d after treatment. Protein blot analysis showed that ketamine-induced P-450 2B1/2 proteins also decreased in a time-dependent manner in 4 d. In hepatotoxicity study, treatment of rats with 1 ml/kg CCl4 produced a 7-fold increase in serum alanine aminotransferase activity level and a 17-fold rise in rats pretreated with 80 mg/kg ketamine for 4 d. Treatment of ICR mice with 120 mg/kg cocaine produced a 17% mortality, whereas the same dose of cocaine produced a 50% mortality in mice pretreated with ketamine. Treatment of mice with 100 mg/kg cocaine produced a 76-fold increase in serum alanine aminotransferase activity level and a 260-fold rise in mice pretreated with 80 mg/kg ketamine for 4 d. The present study shows that ketamine induces the expression of multiple forms of P-450 in rat liver microsomes and increases CCl4-induced liver toxicity and cocaine-mediated acute toxicity. Other potential pharmacological or toxicological events related to ketamine use need to be further explored.

Induction of P450 monooxygenases in the German cockroach, Blattella germanica L

The cytochrome P450 monooxygenases are an important metabolic system whose level of activity can be influenced by several dietary constituents. We examined the effects of six known P450 inducers on the levels of total cytochromes P450, cytochrome b(5), and six monooxygenase activities in adult German cockroaches. In addition, the levels of CYP6L1 and CYP9E2 mRNA were also investigated. Phenobarbital treatment resulted in increases in total cytochromes P450 and metabolism of three resorufin analogues, but not CYP6L1 nor CYP9E2 mRNA. There was no significant effect of the other five inducers on any of the monooxygenase parameters we measured. In comparison with other insects, the German cockroach seems unusually refractory to most inducing agents.

The paradoxical effect of acetaminophen on CYP3A4 activity and content in transfected HepG2 cells

HepG2 cell lines that constitutively and stably express human CYP3A4 were constructed in order to study enzyme interactions with CYP3A4 as the only P450 present. CYP3A4 activity and content were assessed by the metabolism of fentanyl, a CYP3A substrate, and Western blots. Northern blots were used to examine the effects of acetaminophen (APAP) on CYP3A4-mRNA. The HepG2 cell lines' CYP3A4 activity was stable over time. High concentrations of APAP inhibited CYP3A4 activity. At lower concentrations, APAP produced a dose-dependent increase in CYP3A4 activity and content. No increases in CYP3A4-mRNA were seen. Incubation with cycloheximide caused a decrease in fentanyl metabolism secondary to a decrease in P450 levels that was prevented by the coincubation with APAP. Additionally, human microsomal CYP3A4 was stabilized by APAP against cytosol-mediated degradation. In our models, APAP appears to increase CYP3A4 activity. This increase appears to be via substrate stabilization. This is the first report that APAP can increase CYP3A4 activity and content in transfected HepG2 cells.

Gender difference in enzymes related with alcohol consumption in hamster, an avid consumer of alcohol

Syrian golden hamster (Mesocricetus auratus) is extraordinary among laboratory rodents in its ability to drink alcohol. After being given a free choice between 15% ethanol and water for 5 days, both male and female hamsters derived at least 85% of the fluid intake from the ethanol solution. Analysis of the alcohol-metabolizing enzymes in alcohol-naïve hamsters showed that the male had a higher activity of 57%, 58% and 34% in stomach alcohol dehydrogenase, liver cytochrome P450 1A2 and liver aldehyde dehydrogenase, respectively, compared with the female. The activity of lung angiotensin-converting enzyme, which influence fluid intake, was twofold higher in the male. After 4 weeks of ethanol consumption, the activities of the hepatic alcohol-metabolizing enzymes remained unchanged except cytochrome P450 2E1 which increased 42% and 88% in male and female hamsters, respectively. A reduction of approximately 80% in the activity of cytochrome P450 1A2 was observed in both genders. The activities of several other cytochrome P450 enzymes were also decreased. Although ethanol consumption did not increase plasma aminotransferase levels, it caused a significant increase in liver weight in female, but not male hamsters.

Ethanol-mediated CYP1A1/2 induction in rat skeletal muscle tissue

The causes of non-trauma-mediated rhabdomyolysis are not well understood. It has been speculated that ethanol-associated rhabdomyolysis may be attributed to ethanol induction of skeletal muscle cytochrome P450(s), causing drugs such as acetaminophen or cocaine to be metabolized to myotoxic compounds. To examine this possibility, the hypothesis that feeding ethanol induces cytochrome P450 in skeletal muscle was tested. To this end, rats were fed an ethanol-containing diet and skeletal muscle tissue was assessed for induction of CYP2E1 and CYP1A1/2 by immunohistochemical procedures; liver was examined as a positive control tissue. Enzymatic assays and Western blot analyses were also performed on these tissues. In one feeding system, ethanol-containing diets induced CYP1A1/2 in soleus, plantaris, and diaphragm muscles, with immunohistochemical staining predominantly localized to capillaries surrounding myofibers. Antibodies to CYP2E1 did not react with skeletal muscle tissue from animals receiving a control or ethanol-containing diet. However, neither skeletal muscle CYP1A1/2 nor CYP2E1 was induced when ethanol diets were administered by a different feeding system. Ethanol consumption can induce some cytochrome P450 isoforms in skeletal muscle tissue; however, the mechanism of CYP induction is apparently complex and appears to involve factors in addition to ethanol, per se.

Propofol inhibits renal cytochrome P450 activity and enflurane defluorination in vitro in hamsters

PURPOSE

To determine the effect of propofol on renal cytochrome P450 activity and defluorination of enflurane.

METHODS

Renal microsomes were prepared by homogenization and differential centrifugation from pooled hamster kidneys. Defluorination of enflurane was assessed by measuring free fluoride metabolites after reacting enflurane with renal microsomes incubated with various concentrations, 0.05 - 1.0 mmol x L(-1) propofol in the NADPH-generating system. Drug metabolizing activities of renal cytochrome P450 mono-oxygenase enzymes were evaluated within microsomes preincubated with propofol and reacted with the specific marker substrates, aniline, benzo(a)pyrene, erythromycin and pentoxyresorufin, for cytochrome P450 2E1, 1A1, 3A4 and 2B1, respectively.

RESULTS

Renal defluorination of enflurane was inhibited by clinical concentrations, 0.05 mmol x L(-1) of propofol (P < 0.05). Dose-dependent inhibition of defluorination, aniline and benzo(a)pyrene hydroxylase within kidney microsomes was related to propofol concentration. Propofol demonstrated a profound inhibition of renal pentoxyresorufin dealkylase activity even at low concentrations, 0.05 mmol x L(-1) (P < 0.01). Propofol did not exhibit inhibition of erythromycin N-demethylation of kidney microsomes except at high concentration, 1.0 mmol x L(-1). Spectral analyses of key coenzymes of renal cytochrome P450 monooxygenase, cytochrome b5 and cytochrome c reductase, demonstrated an inhibition when incubated with high concentrations of propofol (P < 0.05).

CONCLUSION

In an in vitro study in an NADPH-generating system of hamster kidney microsomes, propofol, in clinical concentrations, exhibited a broad-spectrum of inhibition to renal monooxygenase activities and enflurane defluorination.

The influence of propolis ethanol extract on liver microsomal enzymes and glutathione after chronic alcohol administration

Propolis designates a series of gums, resins and balms of viscous consistency, which are gathered by honeybees from certain parts, mainly the buds and barks of plants, especially those found on coniferous trees. Bees bring propolis back to the hive, where it is modified and mixed with other substances including the bees' own wax and salivary secretions. In this study, the influences of propolis ethanol extract on chronic alcohol induced liver microsomal enzyme changes were investigated. Three grams of alcohol was added to rats' daily diet for four weeks to induce chronic alcohol liver injuries, and two different doses of propolis ethanol extract were p.o. administrated three times per day on the 28th, 29th, and 30th day. During the period of propolis administration, the ethanol diet was continued. After sacrifice, the rat livers were excised for assay of microsomal enzymes activity, glutathione (GSH) concentration, glutathione-S-transferase (GSTase) and gamma-glutamylcysteine synthetase (gamma-GCSase) activity. It was found that 30 mg/kg of propolis ethanol extract significantly prevented the elevations of total cytochrome P-450 enzymes, NADPH-dependent cytochrome C reductase, aniline hydroxylation, 7-ethoxyresorufin hydroxylation (7-ERH), 7-penthoxyresorufin hydroxylation (7-PRH), and lipid peroxidation induced by chronic ethanol administration. Additionally, propolis ethanol extract (100 mg/kg) also induced GSTase and gamma-GCSase activities and decreased glutathione levels in the liver.

Combined effects of ethanol and cigarette smoke on hepatic and pulmonary xenobiotic metabolizing enzymes in rats

The combined effects of ethanol (EtOH) and cigarette smoke (CS) on hepatic and pulmonary monooxygenase (MO) activities (aniline 4-hydroxylase (AH), aminopyrine N-demethylase (AMND), 7-ethoxyresorufin O-deethylase (EROD), p-nitroanisole O-demethylase (p-NAOD)), lipid peroxidation (LP) and reduced glutathione (GSH) levels and glutathione S-transferase (GST) activities toward several substrates (l-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), ethacrynic acid (EAA), 1,2-epoxy-3-(p-nitrophenoxy)-propane (ENPP)) were determined and compared with those of EtOH or CS alone in rats. When the male adult rats (225-275 g) were treated with 10% EtOH (v/v) in their drinking for 21 days AH, AMND and EROD activities and LP and GSH levels increased significantly whereas GST activity for EAA decreased significantly in liver as compared to controls. EtOH did not change the hepatic p-NAOD and GST activities toward CDNB, DCNB and ENPP. In lung, EtOH increased GST activities toward CDNB and ENPP and LP level but decreased GST activity toward DCNB, significantly. No alterations were noted in pulmonary MO activities and GST activity toward EAA and GSH level by EtOH treatment. When the animals were exposed to CS five times a day, with 1 h intervals, for 3 days in a chamber where smoke and fresh air lead alternatively, AMND, EROD and p-NAOD activities, GST activity toward EAA and GSH level increased but LP level and GST activity for ENPP decreased significantly in liver. CS did not alter the hepatic AH and GST activities toward CDNB and DCNB. In lung, CS increased AH, EROD and p-NAOD activities and LP and GSH levels and decreased all the GST activities studied significantly. CS had no influence on pulmonary AMND activity. For the combined treatment, the animals were treated with 10% EtOH (v/v) in their drinking water for 21 days and during the last 3 days they were exposed to CS five times a day, with 1 h intervals, in a chamber where smoke and fresh air lead alternatively. In these animals, augmentation of elevations were noted in AH and p-NAOD activities and LP and GSH levels but not in EROD and AMND activities in liver. Combined treatment significantly decreased GST activity toward CDNB, ameliorated the alteration caused by either EtOH or CS treatment alone on GST activity toward EAA and potentiated the depression of GST activity toward ENPP to a greater degree. No change was observed in GST activity toward DCNB. In lung, combined treatment potentiated the elevations of AMND and p-NAOD activities and LP level and not those of AH and EROD activities. GST activities toward CDNB, DCNB and ENPP were highly elevated by the combined treatment. No changes were observed in pulmonary GSH level and GST activity for EAA by the combined treatment. These results reveal that the regulations of the hepatic and pulmonary MO and GST are differentially influenced by EtOH, CS and the combined treatment.

Gender differences in ethanol oxidation and cytochrome P4502E1 content and functions in hepatic microsomes from alcohol-preferring and non-preferring rats

1. We have studied the hepatic microsomal metabolism of ethanol (MEOS), CYP2E1 expression and catalytic activity, and the response to phenobarbital (PB) induction or CCl4 challenge in rats of either sex genetically selected for their preference (P) or aversion (NP) for ethanol. 2. In P versus NP females, the amount of both total cytochrome P450 and P450 binding to metyrapone was lower, whereas the activities of MEOS, aniline 4-hydroxylase (4-AOH), and 4-nitrophenol hydroxylase (PNP-OH) as well as the level of immunodetectable CYP2E1 content were consistently higher. By contrast, no substantial differences were observed between P and NP males. 3. Despite an apparent down-regulation of CYP2E1 expression occurring in all rats as a result of PB induction, P females maintained higher 2E1 levels and showed enhanced MEOS, 4-AOH and PNP-OH activities with respect to NP females. No such changes were detected in the male counterparts. 4. No sex-related differences in CCl4-mediated inhibition of monooxygenase or MEOS activities were evident between P and NP animals. 5. These results indicate that, in females only, the behavioural trait of ethanol preference is apparently associated not only with higher constitutive levels of CYP2E1 and rate of microsomal metabolism of ethanol but also with altered susceptibility to PB induction.

Induction of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) activation in rat lung microsomes by chronic ethanol consumption and repeated running exercise

The effects of both chronic ethanol consumption and repeated exercise on metabolism of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by rat lung microsomes were investigated. Keto aldehyde production was significantly enhanced 52% and 98%, respectively, by the ethanol and exercise, as was keto alcohol production (72% and 76%). 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) production was significantly enhanced only by the exercise (+32%). The combined treatment enhanced the keto alcohol production by 39%, indicating non-additive effects on cytochrome P450 (CYP) isozymes by the different treatments. Immunoblot and metabolic studies revealed an increased activity and content of CYP1A2 and CYP2B induced by the ethanol and exercise treatments as well as an induction of CYP2E1 proteins by the ethanol and combined treatments. These results indicate that both ethanol consumption and running exercise enhance NNK activation by increasing the expression of the CYP enzymes responsible for NNK activation.

The involvement of cytochrome P4502E1 in 2-bromoethanol-induced hepatocyte cytotoxicity

The cytotoxicity of 2-bromoethanol towards hepatocytes isolated from rats was concentration-dependent (EC(50)100 mu M, 2 hr). Bromoacetaldehyde was more toxic (EC(50)60 mu M, 2 hr) and bromoacetic acid was less toxic (EC(50)150 mu M, 2 hr). Glutathione (GSH) depletion occurred before cytotoxicity ensued and GSH depleted hepatocytes were more susceptible to 2-bromoethanol. Lipid peroxidation increased steadily 1 hr after 2-bromoethanol addition and antioxidants, iron chelators or hypoxia prevented 2-bromoethanol induced lipid peroxidation and cell lysis. Alcohol dehydrogenase inhibitors, methyl pyrazole or dimethyl sulfoxide only partly prevented 2-bromoethanol induced GSH depletion, lipid peroxidation and cytotoxicity. However, cytochrome P4502E1 (CYP2E1) inhibitors/substrates were more effective at preventing 2-bromoethanol-induced GSH depletion, lipid peroxidation and cytotoxicity suggesting that 2-bromoethanol is mostly metabolically activated by CYP2E1. Also, hepatocytes isolated from CYP2E1 induced rats were more susceptible to 2-bromoethanol and hepatocytes isolated from rats pretreated with carbon disulfide to inactivate CYP2E1 were more resistant to 2-bromoethanol treatment. Formation of S-(formylmethyl)glutathione during 2-bromoethanol metabolism by microsomal mixed function oxidase in the presence of GSH was also prevented by cytochrome P4502E1 inhibitors/substrates or by Anti-Rat CYP2E1. Furthermore, aldehyde dehydrogenase inhibitors-cyanamide or chloral hydrate increased 2-bromoethanol dependent hepatocyte susceptibility. This suggests that 2-bromoethanol is preferably metabolised by CYP2E1 dependent monoxygenase to form 2-bromoacetaldehyde which causes cell lysis as a result of GSH depletion and lipid peroxidation.

Induction and suppression of renal and hepatic cytochrome P450-dependent monooxygenases by acute and chronic streptozotocin diabetes in hamsters

The acute and chronic effects of streptozotocin diabetes on kidney and liver microsomal monooxygenases were studied using hamsters 2 days and 6 weeks following treatment with the diabetogen, respectively. Acute diabetes increased aniline hydroxylation and N-nitrosodimethylamine demethylation, decreased pentoxyresorufin O-dealkylation, without affecting benzo(a)pyrene hydroxylation and 7-ethoxycoumarin O-deethylation in kidney and liver microsomes. The effects of chronic diabetes on the microsomal monooxygenases were similar to the effects of acute diabetes, except that the chronic diabetic condition markedly decreased benzo(a)pyrene and 7-ethoxycoumarin oxidations in kidney microsomes. Total cytochrome P450 content and NADPH-cytochrome P450 reductase activity in kidney and liver microsomes of the diabetic hamsters were similar to the controls. Gel electrophoresis of microsomes from control and streptozoptocin treated hamster tissues revealed that diabetes enhanced the intensity of protein band(s) in the P450 molecular weight region. Immunoblotting of microsomal proteins showed that acute and chronic streptozotocin diabetes induced proteins immunorelated to P450s 2E1 and 1A in kidney and liver. In marked contrast, the acute and chronic diabetic conditions decreased the level of a P450 2B-immunorelated protein(s) in kidney and liver. The present study demonstrates that acute and chronic streptozotocin diabetes has the ability to induce P450 2E1 and 1A and suppress P450 2B in hamster kidney and liver and that the hamster monooxygenase responds to diabetes differently from the rat enzyme.

Alcohol-related cancer risk: a toxicokinetic hypothesis

Consumption of alcoholic beverages is an accepted social custom world-wide. This makes its involvement in events contributing to human cancer risk very important. Although it is neither tumorigenic nor genotoxic in animals, ethanol can potentiate the carcinogenic risk associated with certain environmentally present agents. The reasons for such a synergistic action are speculative, but among theories postulated may be ethanol's ability to modify the toxicokinetics/dynamics of carcinogen metabolism. Experiments conducted with rodents and primates support this hypothesis, demonstrating increased exposure of posthepatic organs to nitrosamines when given in combination with ethanol, followed by enhancement of DNA adduct formation and, at least in rodents, of tumor development. In addition, ethanol may induce enzymes responsible for carcinogen activation, including hepatic cytochrome P450 2E1 in rodents and humans, and in lung, kidney, and brain in rodents. Studies have also shown that these effects can extend to the next generation via maternal and in utero fetal exposure. What impact such ethanol-induced modulations have on tumorigenesis during childhood and later stages of life needs to be investigated further.

Tissue and sex-dependent differences in CYP2A activities in hamsters

Three enzymatic activities of the CYP2A subfamily, coumarin 7-hydroxylase (COH), testosterone 15 alpha-hydroxylase (T15 alpha OH) and testosterone 7 alpha-hydroxylase (T7 alpha OH), were characterized in liver, kidney and lung microsomes from control, pyrazole (PYR), 3-methylcholanthrene (MC) and phenobarbital (PB) treated female and male Syrian golden hamsters. Sex-dependent changes in the enzymatic activities were found. Among control animals COH and T15 alpha OH activities were higher in males. T7 alpha OH activity was five times higher in female kidneys than in males. Inducers changed this metabolic profile. MC and PB were potent CYP2A inducers in extrahepatic tissues: significant increases were found in COH (5-fold) and T15 alpha OH (12-fold) activities in female MC lung microsomes and T7 alpha OH (7-fold) in MC male kidney microsomes. PB increased significantly activities of COH (5-fold), T15 alpha OH (3-fold) and T7 alpha OH (10-fold) in male kidney microsomes. All inducers significantly increased T7 alpha OH activity in male kidney microsomes but decreased hepatic T7 alpha OH activity in both sexes. PYR treatment decreased hepatic CYP2A activities. Anti-mouse CYP2A4/5 antibody inhibited COH activity by a variable extent depending on the tissue and pretreatment and recognised three 52-, 49-, 48-kDa bands in liver and two major bands in kidney (48 and 49 kDa) and lung (49 and 52 kDa) microsomes. COH and T15 alpha OH activities correlated well with 49 kDa protein (r = 0.95 and r = 0.99, respectively) in lung microsomes.(ABSTRACT TRUNCATED AT 250 WORDS)