Effects of chlorinated paraffins on liver weight,cytochrome P-450 concentration and microsomal enzyme activities in chick embryos

Sublethal doses of three technical preparations of chlorinated paraffins (CPs) (Cereclor 42 (C_22–26, 42% Cl w/w), Cereclor 50LV (C_10–13, 49% Cl w/w) and Cereclor 70L (C_10–13, 70% Cl w/w)) were injected into the yolks of hens' eggs after 4 days of incubation. The liver weight, the cytochrome P-450 concentration in the liver and the liver microsomal activity of aminopyrine N-demethylase (APND), aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH) and 7-ethoxycoumarin O-deethylase (ECOD) were determined in chick embryos incubated for 20 days. The degree of chlorination and probably also the carbon chain length of the CPs were of importance for their effects. Cereclor 70L was the most potent in causing increases in liver weight, cytochrome P-450 concentration and APND activity. Cereclor 42 was the least potent in these respects, even causing reduced APND activity. A decrease in AHH activity occurred in chick embryos treated with Cereclor 50LV, and a reduction in ECOD activity was noted as a result of treatment with Cereclor 42 and Cereclor 50LV.     

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. Received: 27 March 1995 / Accepted: 4 July 1995     

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

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-deethylations of ethoxycoumarin and ethoxyresorufin. The antifungal-induced O-deethylation of ethoxycoumarin was much more sensitive to inhibition by metyrapone rather than by -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.     

Effects of dioxane on cytochrome P450 enzymes in liver, kidney, lung and nasal mucosa of rat

The effect of acute and chronic dioxane administration on hepatic, renal, pulmonary and nasal mucosa P450 enzymes and liver toxicity were investigated in male rats. The acute treatment consisted of two doses (2 g/kg) of dioxane given for 2 days by gavage, whereas the chronic treatment consisted of 1.5% of dioxane in drinking water for 10 days. Both the acute and chronic dioxane treatments induced cytochrome P450 2B1/2- and P450 2E1-dependent microsomal monooxygenase activities (pentoxyresorufin O-depentylase and p-nitrophenol hydroxylase) in the liver, whereas in the kidney and nasal mucosa, only the 2E1 marker activities were enhanced. In addition in the liver, an induction of 2-testosterone hydroxylase (associated with the constitutive and hormone-dependent P450 2C11) was also revealed, whereas the hepatic P450 4A-dependent -lauric acid hydroxylase was not enhanced by any dioxane treatment. These inductions were mostly confirmed by western blot analysis of liver, kidney and nasal mucosa microsomes. In the lung, no alteration of P450 activities was observed. To assess the mechanism of 2E1 induction, the hepatic, renal and nasal mucosa 2E1 mRNA levels were also examined. Following two kinds of dioxane administration, in the liver the 2E1 induction was not accompanied by a significant alteration of 2E1 mRNA levels, while both in the kidney and nasal mucosa the 2E1 mRNA increased about 2- to 3-fold, indicating an organ-specific regulation of this P450 isoform. Furthermore, dioxane was unable to alter the plasma alanine aminotransferase activity and hepatic glutathione (GSH) content, examined as an index of toxicity, when it was administered into rats with P450 2B1/2 and 2E1 preinduced by phenobarbital or fasting pretreatment. These results support the lack of or a poor formation of reactive and toxic intermediates during the biotrasformation of this solvent, even when its metabolism was enhanced by P450 inducers. The chronic administration of dioxane was also unable to induce the palmitoyl CoA oxidase, a marker of peroxisome proliferation, excluding this as a way to explain its toxicity. Thus, although the mechanism of dioxane carcinogenicity remains unclear, the present results suggest that the induction of 2E1 following a prolonged administration of dioxane might provide oxygen radical species, and thereby contribute to its organ-specific toxicity.     

Distribution and induction of cytochrome P-450 and two cytochrome P-450-dependent monooxygenase activities in rat liver parenchymal cell subpopulations separated by centrifugal elutriation

Liver parenchymal cells from the periportal and centrilobular zones differ in their morphological, biochemical and functional characteristics. In an effort to obtain fractions enriched in either periportal or centrilobular cells, isolated rat liver parenchymal cells were separated into five subpopulations by centrifugal elutriation. The mean diameters of the cells present in fractions I–V were 19.6, 21.1, 21.8, 22.7 and 23.5 m, respectively. The content of cytochrome P-450 as well as benzphetamine N-demethylase and 7-ethoxyresorufin O-deethylase activities were higher in the larger parenchymal cells than in the smaller ones. After administration of phenobarbital the content of cytochrome P-450 was approximately two-fold greater in the cells present in fractions 3–5, when compared to the same subpopulations isolated from untreated rats; the activity of benzphetamine N-demethylase was enhanced to a similar extent in all five fractions. 3-Methylcholanthrene treatment resulted in a significant increase of cytochrome P-450 content and 7-ethoxyresorufin O-deethylase activity in all five fractions: both parameters were slightly higher in fractions 4 and 5 than in fractions 1 and 2. In conclusion, the elutriated liver parenchymal cells seem to preserve the biochemical heterogeneity observed in the intact liver; the potential enrichment of periportal and centrilobular cells in the different fractions by centrifugal elutriation is discussed.     

Comparative effects of ethanol administration on hepatic monooxygenases in rats and mice

The inducing effects of chronic ethanol ingestion on hepatic monooxygenases in Sprague-Dawley and Long-Evans rats, and A/J and C57BL/6J mice, were studied. Cytochrome P-450 content was significantly increased in livers of all animals receiving the experimental ethanol-containing liquid diet. The CO-difference spectra of microsomes from ethanol-treated animals showed a shift in the absorbance maximum to 451–452 nm, compared to the absorbance maximum of 450 nm observed with microsomes from control animals. Ethylmorphine N-demethylase and benzo[a]pyrene hydroxylase activities in livers of ethanol-treated animals were minimally affected. The shift in the absorbance maxima to longer wavelengths in the CO-difference spectrum and the minimal effects on the metabolism of ethylmorphine and benzo[a]pyrene demonstrate that ethanol differs in its inducing properties, when compared to the properties of the two widely used hepatic microsomal enzyme inducers, phenobarbital and 3-methylcholantrhene. In contrast to the minimal effects observed on the metabolism of ethylmorphine and benzo[a]pyrene, several fold increases were observed in hepatic 7-ethoxycoumarin 0-deethylase and aniline hydroxylase activities in the treated animals. Polyacrylamide gel electrophoresis of hepatic microsomes from those animals receiving ethanol revealed protein band(s) in the cytochrome P-450 molecular weight region, the intensities of which were markedly increased relative to that from control animals. The heme-associated peroxidase activity was also increased in the same molecular weight region. The results of the present spectral, catalytic, and electrophoretic studies demonstrate that in mice, as in rats, chronic ethanol treatment causes the induction of specific cytochrome(s) P-450 with preferential activity toward aniline and 7-ethoxycoumarin.     

Effects of polychlorinated terphenyls and paraffins on rat liver microsomal cytochrome P-450 and in vitro metabolic activities

The polychlorinated terphenyl Aroclor 5460 and the polychlorinated paraffins Witaclor 171 P and Witaclor 149 increased to different degrees the total microsomal concentration of cytochrome P-450 in the rat liver after intraperitoneal injection of 0.3, 1.0, and 1.0 g · kg^–1 body weight, respectively, each day for four days. The multiple forms of cytochrome P-450 were affected differently with an induction of RLvMc P-450₅₀ and RLvMc P-450₅₄ by all chemicals, and an additional induction of RLvMc P-450₅₅ by the polychlorinated terphenyl. The rat liver weights were extensively increased after treatment with the polychlorinated paraffins. Alterations were found in the in vitro metabolism of biphenyl, benzo(a)pyrene and the steroid hormones, 4-androstene-3,17-dione and 5-androstane-3,17-diol, after exposure to all chemicals. Changes in the in vitro formation of benzo(a)pyrene metabolites were found to correlate with changes in the multiple forms of cytochrome P-450. The present study demonstrate that only limited information can be obtained from alterations in the total concentration of cytochrome P-450 and show the importance of studying changes in the multiple forms and the metabolism of different substrates. Our results further indicate that exposure to any of the investigated polychlorinated chemicals may alter the biological effects of other environmental contaminants, drugs and endogenous substances which are metabolized by the cytochrome P-450 enzyme system.     

Differences in cytochrome P-450 of various strains of rats following chronic administration of pentobarbital.

Cytochrome P-450 levels were analyzed in rats of two pigmented (black Long-Evans and ACI) and two albino strains (Fischer 344 and Sprague-Dawley) following the administration of pentobarbital sodium and physiological saline. Differences between the albino vs pigmented strains were observed following injections of saline. The Fischer 344 albino strains responded similarly to the pigmented strains following a progressively increasing dose schedule of pentobarbital sodium.     

Interlaboratory comparison of total cytochrome P-450 and protein determinations in rat liver microsomes

Assay conditions in determining total cytochrome P-450 in four laboratories were compared. Although the determination was derived from the original Omura and Sato method in each laboratory, the four standard protocols differed slightly, resulting in considerable differences in the results. Since the cytochrome P-450 content is usually expressed per mg protein, the protein assay conditions were evaluated as well. Furthermore, we compared the cytochrome P-450 values obtained by the CO- and the dithionite (DT)-difference methods. The effect of a number of variables in the assay was investigated. The influence of the storage temperature of the microsomes was ascertained as well as effects of the gassing time with CO and the time between addition of dithionite, CO-gassing and the recording of the difference spectra. After evaluating these variables a standard operation procedure was established. Using this procedure the interlaboratory coefficient of variation for total cytochrome P-450 was 4.8%, a value which was comparable to the intralaboratory coefficients of variation. The final results also show that the millimolar extinction coefficient for the DT-difference method is higher than for the CO-difference method.     

Effect of cytochrome P-450 inhibitors on pharmacokinetics and safety of voriconazole

Our objective was to systematically assess the effect of cytochrome P-450 (CYP450) inhibitors on pharmacokinetics and safety of voriconazole (VORI). Cochrane Library, PubMed, Embase, CNKI, CBM and WanFang databases and Clinicaltrials. gov were searched up to Jan. 26th 2016. Two reviewers independently identified studies, extracted data and assessed quality of studies. Meta-analysis was performed with RevMan 5.3, and risk ratios (RRs) and mean differences (MDs) with 95% confidence intervals (CIs) were calculated. A total of 12 studies were included: three crossover randomized controlled trials, three single-arm before-and-after studies and six cohort studies. Compared with non-combination group, the group of VORI plus omeprazole had a significantly higher occurrence of hepatic dysfunction (RR = 4.11, 95% CI 1.12–15.08, P = 0.03). However, neurologic dysfunction and visual disturbance were not significantly different. Pantoprazole, rabeprazole, cimetidine and contraceptive significantly increased the peak concentration (Cmax) and area under the curve (AUC) of VORI, while indinavir had no significant effect on pharmacokinetics of VORI. The effects of esomeprazole, erythromycin and azithromycin on pharmacokinetic parameters of VORI presented inconsistent results. Co-administration of VORI and CYP450 inhibitors was safe except for omeprazole. Although Cmax and AUC of VORI were increased while co-administered with a couple of CYP450 inhibitors, no significant effect on clinical outcomes was observed.     

黄酮类化合物对细胞色素P450 CYP1，2E1，3A4和19的影响

黄酮类化合物广泛存在于蔬菜、坚果、水果和饮料及中草药中，可诱导或抑制多种细胞色素P450的活性。本篇综述主要集中回顾黄酮类化合物对于细胞色素P450 CYP1，2E1，3A4和19的影响。归纳总结了该类物质抑制和诱导细胞色素P450的多种机制，如刺激特定的受体、稳定相关mRNA等。并总结了该类物质对细胞色素P450的影响体内和体外水平的研究结果并非总是一致的原因，如体内外的浓度的差异、基因和其他环境因素的影响。由于黄酮类化合物可通过影响细胞色素P450的活性影响药物代谢从而导致药物不良反应和药物相互作用，因此在将该类物质与其他药物合用时应高度重视。     

Fingerprinting rat liver microsomal cytochromes P-450 as a means of delineating sexually distinctive forms

The cytochrome P-450 fraction of microsomes separated on lauric acid AH-Sepharose 4B columns contains about 75% of the microsomal P-450. This was finger-printed by means of two dimensional isoelectric focusing/ SDS-PAGE. Separation of the fraction by highly reproducible, standard procedures on carboxymethyl Sepharose CL6B into four fractions allowed ready isolation and purification of seven forms of P-450, RLM2, 2b, 3, f4, 5, 5a and f5a. Comparison of the four fractions CMI, CMII, CMIII and CMIV revealed qualitative differences in the proteins contained in CMI and CMII of male and female rats. Identification of these proteins revealed RLM2, present in the CMI fraction of adult male rats, is not present in detectable levels in the comparable fraction from females. Similarly, RLM3 and 5 were present in the CMII fraction of male rats but could not be detected in the corresponding fraction of females. Instead, another protein, fRLM4, was found in the females. RLM5a, found in the CMII fraction of males, was also present in females. Examination of the physical properties of these P-450 proteins revealed those isolated in the CMI and CMII fractions to have fairly neutral isoelectric points (7.1–7.6). Based upon the NH₂-terminal amino acid sequence, three classes of constitutive forms of P-450 can be recognized. All of the constitutive forms have methionine in position one and leucine in position seven. By comparing sequence homologies, RLM2 and 2b form one sub-class, RLM3, f4 and 5 form a second sub-class, and P-450f and RLM5a form a third sub-class.Dedicated to Professor Dr. med. Herbert Remmer on the occasion of his 65th birthdayThis work was supported by United States Public Health Service Grant GM26114 from the National Institutes of Health     

Stimulatory effects of benzene on rabbit liver and kidney microsomal cytochrome P-450 dependent drug metabolizing enzymes

Treatment of rabbits with benzene (880 mg/kg/day), s.c. for 3 consecutive days, caused 3.8- and 5.7-fold increases in aniline 4-hydroxylation rates of liver and kidney microsomes, respectively. Benzene treatment markedly enhanced hydroxylation rates ofp-nitrophenol by liver and kidney by 7.2- and 4.2-fold, respectively. Both of these enzymes are associated with cytochrome P-450 LM3a. In contrast, the activity of benzphetamine N-demethylase, associated with P-450 LM2, was not altered significantly in either liver or kidney microsomes. Although the total cytochrome P-450 contents of liver and kidney microsomes were not altered significantly by the benzene treatment, in the case of liver microsomes, formation of a new cytochrome P-450 with an apparent M_r of 51,400 was observed on SDS-PAGE. On the other hand, in the kidney microsomes, the intensity of the bands corresponding to approximate M_r of 50000 and 51400 was markedly increased. The results of the present work, in combination with those of the previous work (Arinç et al. 1988), indicate the existence of tissue specificity in the induction of rabbit P-450 isozyme by benzene.A preliminary account of this work has been presented at the Nato Advanced Study Institute on Molecular Aspects of Monooxygenases and Bioactivation of Toxic Compounds, August 27–September 7, 1989, Izmir, Turkey.     

Alteration of cytochrome P-450 by prolonged administration of imipramine and/or lithium to rats

Summary The aim of this study was to investigate imipramine-induced alterations of cytochrome P-450 and to determine whether prolonged concomitant administration of imipramine and lithium results in a pharmacokinetic interaction.Male Wistar rats received imipramine (10 mg/kg i. p.) at 12 h intervals or lithium chloride (100 mg/kg in drinking water) or they were treated with the combination of these drugs for 2 weeks. The long term treatment with imipramine produced a very complex alteration of cytochrome P-450: imipramine increased the level of the cytochrome, but it decreased the rate of its own aromatic hydroxylation in position 2. The rate of N-demethylation in the side chain was not changed. Consequently, in the case of both hydroxylation and demethylation, calculated molecular activities were decreased to 48% and 70% respectively. This differential change in activities corresponded well to the observed decrease of absorption in difference spectra (type I) produced in microsomes by imipramine. Carbamazepine-induced type I difference spectra were also decreased by imipramine pretreatment, but to a lesser extent. In contrast, hexobarbital type I binding was increased by imipramine treatment while type II difference spectra produced by metyrapone were not affected. The preliminary SDS-PAGE analysis of cytochrome P-450 isoenzymes of control and imipramine treated rats showed that the investigated antidepressant markedly intensified a protein band at 50.11 kD while bands at 51.28 kD, 56.20 kD and 56.88 kD were less intensive. These results indicate that the alteration of cytochrome P-450 by imipramine treatment is not only of quantitative but also of qualitative character. Lithium alone given to rats affected neither the concentration of cytochrome P-450 in microsomal protein nor the rate of imipramine metabolism in vitro. Lithium given jointly with imipramine reduced imipramine-induced elevation of cytochrome P-450. This, however, did not cause any change in the rate of imipramine metabolism in vitro and accordingly in imipramine pharmacokinetics in vivo. The concentration of lithium in the blood plasma tended to increase by concurrent administration of imipramine.Send offprint requests to K. J. Netter at the above address     

Alcohol-inducible cytochrome P-450 (P-450ALC)

Of the family of P-450 cytochromes occurring in rabbit liver microsomes, only isozyme 3 a (P-450_ALC) is induced by alcohol administration and is effective in catalyzing the reaction: ethanol+0₂+NADPH+H⁺ acetaldehyde +2H₂O+NADP⁺. As judged by immuno-chemical quantitation, P-450_ALC is also induced in the animals by other diverse agents, including imidazole, trichlorethylene, acetone, pyrazole, and isoniazid. Evidence has been obtained for the occurrence of a protein immuno-chemically related to P-450_ALC in human liver microsomes and of a similar alcohol-inducible protein in the rat and in the normal and alcohol dehydrogenase-deficient deer-mouse. P-450_ALC catalyzes the activation of foreign compounds such as acetaminophen, various nitrosamines, and carbon tetrachloride and is therefore believed to play an important role in the enhanced toxicity of these substances accompanying alcohol administrationDedicated to Professor Dr. Herbert Remmer on the occasion of his 65th birthday     

Species of cytochrome P-450 in rat liver microsomes with different stereoselectivity for the binding and monooxygenation of (+)- and (−)-methylphenobarbital

Summary N-Demethylation to phenobarbital is the only detectable monooxygenation pathway for (+)- and (–)-methylphenobarbital in rat liver microsomes. In microsomes from control ratsV _max is about 3.5-fold higher for the (+)-isomer than for the (–)-form. This ratio increases significantly to 5 after pretreatment of rats with phenobarbital. Qualitatively similar but smaller ratios are found for the magnitude of the substrate binding spectra with corresponding values of 1.7 for control and 2.5 for phenobarbital treated rats.The spectral dissociation constants (K _s) and the distribution of both enantiomers between water and the microsomal membranes are not significantly different. Since only cytochrome P-450 is involved in the N-demethylation of both enantiomers the participation of two phenobarbital-inducible species of cytochrome P-450 with different Stereoselectivity is suggested. This is proved by inhibition studies with metyrapone which forms complexes more easily with the species responsible for the preferential binding and N-demethylation of the (+)-isomer of methyl phenobarbital.This work was supported by the Deutsche Forschungsgemeinschaft, Schwerpunktsprogramm: Struktur und Funktion biologischer Membranen. We thank Prof. Dr. J. Knabe for the generous gift of (+)- and (-)-methylphenobarbital and Prof. Dr. W. Rummel and Dr. H. Büch for helpful discussions.     

Characterization of hepatic and pulmonary cytochromes P-450 in 3-methylcholanthrene-treated hamsters

Two major forms of hepatic cytochrome P-450 (hepatic P-450_MCI and P-450_MCII) were purified approximately 5-fold from liver microsomes in Syrian golden hamsters treated with 3-methylcholanthrene (MC). The purified preparations of hepatic P-450_MCI and P-450_MCII contained 9.6 and 8.3 nmol cytochrome P-450 (P-450) per mg protein, respectively, and were essentially free from NADPH-cytochrome c (P-450) reductase (fpT), NADH-cytochrome b₅ reductase and cytochrome b₅. By sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the molecular weights of hepatic P-450_MCI and P-450 _mMCII were estimated to be 56 000 and 53 500. Further, a major form of pulmonary P-450 (P-450_MC) were purified from lung microsomes of MC-treated hamster, and contained 14.2 nmol P-450 per mg protein, and estimated to be 56 000 in monomeric molecular weight, indicating the similar molecular weight to hepatic P-450_MCI in the hamster. From the absorption spectra the oxidized forms of hepatic P-450_MCI and P-450_MCII were high- and low-spin ferric hemoproteins, respectively, and pulmonary P-450_MC was similar to hepatic P-450_MCII in their hemoprotein spin state. No difference, however, was observed in the CO-reduced forms among hepatic P-450_MCI, P-450_MCII and pulmonary P-450_MC, all exhibiting 446.5 nm Soret bands. In a reconstituted system containing fpT and dilauroylphos-phatidylcholine (DLPC), pulmonary P-450_MC efficiently catalyzed benzo[a]pyrene (BP) hydroxylation at a rate of 11.4 mol formed per min per mol P-450, but hepatic P-450_MCI and P-450_MCII both exhibited lower levels, e. g., 0.49 and 0.54, respectively. These findings indicated a clear tissue difference in the activity of BP hydroxylation between lung and liver in MC-treated hamsters.Dedicated to Professor Dr. med. Herbert Remmer on the occasion of his 65th birthday     

Induction of cytochrome P450 1A in hamster liver and lung by 6-nitrochrysene

The present study has determined the effect of 6-nitrochrysene (6-NC) on hepatic and pulmonary cytochrome P450 (P450)-dependent monooxygenases using hamsters pretreated with the nitrated polycyclic aromatic hydrocarbon (nitro-PAH) at 5 mg/kg per day for 3 days. Pretreatment with 6-NC elevated serum gamma-glutamyltranspeptidase, lactate dehydrogenase, and bilirubin levels. Liver S9 fractions prepared from controls and hamsters pretreated with 6-NC markedly increased mutagenicity of the nitro-PAH in Salmonella typhimurium tester strains TA98, TA100, and TA102. The pretreatment selectively increased 1-nitropyrene reductase activities of lung cytosol and liver and lung microsomes. Pretreatment with 6-NC resulted in increases of microsomal 7-ethoxyresorufin and methoxyresorufin O-dealkylases activities in liver and lung without affecting the monooxygenase activities in kidney. Immunoblot analysis of microsomal proteins using mouse monoclonal antibody 1–12–3 to rat P450 1A1 revealed that 6-NC induced P450 1A-immunorelated proteins in liver and lung. RNA blot analysis using mouse P450 1A1 cDNA showed that 6-NC increased liver and lung P450 1A mRNA. 6-NC had no effect on the kidney P450 protein and mRNA. The present study demonstrates that the hamster enzymes can support 6-NC metabolic activation and the nitro-PAH induces liver and lung P4501A via a pretranslational mechanism. Received: 5 January 1998 / Accepted: 25 February 1998