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PubMed1988

Human liver cytosolic epoxide hydrolases.

Human liver epoxide hydrolases were characterized by several criteria and a cytosolic cis-stilbene oxide hydrolase (cEHCSO) was purified to apparent homogeneity. Styrene oxide and five phenylmethyloxiranes were tested as substrates for human liver epoxide hydrolases. With microsomes activity was highest with trans-2-methylstyrene oxide, followed by styrene 7,8-oxide, cis-2-methylstyrene oxide, cis-1,2-dimethylstyrene oxide, trans-1,2-dimethylstyrene oxide and 2,2-dimethylstyrene oxide. With cytosol the same order was obtained for the first three substrates, whereas activity with 2,2-dimethylstyrene oxide was higher than with cis-1,2-dimethylstyrene oxide and no hydrolysis occurred with trans-1,2-dimethylstyrene oxide. Generally, activities were lower with cytosol than with microsomes. The isoelectric point for both microsomal styrene 7,8-oxide and cis-stilbene oxide hydrolyzing activity was 7.0, whereas cEHCSO had an isoelectric point of 9.2 and cytosolic trans-stilbene oxide hydrolase (cEHTSO) of 5.7. The cytosolic epoxide hydrolases could be separated by anion-exchange chromatography and gel filtration. The latter technique revealed a higher molecular mass for cEHCSO than for cEHTSO. Both cytosolic epoxide hydrolases showed higher activities at pH 7.4 than at pH 9.0, whereas the opposite was true for microsomal epoxide hydrolase. The effects of ethanol, methanol, tetrahydrofuran, acetonitrile, acetone and dimethylsulfoxide on microsomal epoxide hydrolase depended on the substrate tested, whereas both cytosolic enzymes were not at all, or only slightly, affected by these solvents. Effects of different enzyme modulators on microsomal epoxide hydrolase also depended on the substrates used. Trichloropropene oxide and styrene 7,8-oxide strongly inhibited cEHCSO whereas cEHTSO was moderately affected by these compounds. Immunochemical investigations revealed a close relationship between cEHCSO and rat liver microsomal, but not cytosolic, epoxide hydrolase. Interestingly, cEHTSO has no immunological relationship to rat microsomal, nor to rat cytosolic epoxide hydrolase. cEHTSO from human liver differed also from its counterpart in the rat in that it was only moderately affected by tetrahydrofuran, acetonitrile and trichloropropene oxide. Five steps were necessary to purify cEHCSO. The enzyme has a molecular mass (49 kDa) identical to that of rat liver microsomal epoxide hydrolase.

Adult↗
PubMed2003

Induction of multidrug resistance protein 3 (mrp3) in vivo is independent of constitutive androstane receptor.

We previously demonstrated that multidrug resistance protein 3 (Mrp3/ABCC3) is induced in rat liver by phenobarbital (PB) and several other microsomal enzyme inducers that induce cytochrome P450 2B (CYP2B). CYP2B is induced by constitutive androstane receptor (CAR)-retinoid X receptor (RXR) heterodimer binding to a phenobarbital-responsive promoter element in the CYP2B promoter. Hepatic mRNA levels of CYP2B and Mrp3 were measured in three models of altered CAR activity to determine whether CAR is also involved in the induction of Mrp3. In Wistar Kyoto rats, where males express higher CAR protein levels than females, the induction of CYP2B1/2 was significantly higher in males than in females by PB, diallyl sulfide, and trans-stilbene oxide but not oltipraz. Mrp3 was induced by each of these treatments, but in contrast to CYP2B1/2, to a similar magnitude in males and females. In male hepatocyte-specific RXRalpha-/- mice, CYP2B10 was not induced by diallyl sulfide or oltipraz but remained inducible by PB and trans-stilbene oxide after considering the decrease in basal CYP2B10 expression. Mrp3, however, was induced by PB, diallyl sulfide, trans-stilbene oxide and oltipraz in both wild-type and RXRalpha-/- mice. Additionally, constitutive expression of Mrp3 was significantly reduced in RXRalpha-/- mice. In CAR-/- mice, the robust induction of CYP2B10 by PB was completely absent. However, Mrp3 was equally induced both in wild-type and CAR-/- mice by PB. These data clearly demonstrate that induction of hepatic Mrp3 by PB and other microsomal enzyme inducers is CAR-independent and implies a role for RXRalpha in the constitutive expression of Mrp3.

Animals↗
PubMed2005

ClC-3-independent sensitivity of apoptosis to Cl- channel blockers in mouse cardiomyocytes.

It has been shown that Cl-/HCO3- exchangers and Cl- channels, both of which are sensitive to stilbene derivatives, have essential roles in the mechanism of apoptosis induction. Staurosporine-induced apoptosis in neonatal mouse cardiomyocytes was prevented by a stilbene derivative, DIDS. To clarify whether Cl-/HCO3- exchangers or Cl- channels are targets of DIDS and whether ClC-3 is involved in the apoptotic process, staurosporine-induced reduction of cell viability, DNA laddering and caspase-3 activation were examined in cultured mouse ventricular myocytes derived from wild-type and ClC-3-deficient mice. Staurosporine-induced apoptosis and its DIDS sensitivity in ambient HCO3(-)-free conditions in which operation of Cl-/HCO3- exchangers is minimized were indistinguishable from when HCO3- was present. Apoptosis was also prevented by application of a non-stilbene-derivative Cl- channel blocker, NPPB, which cannot block Cl-/HCO3- exchangers. Cardiomyocytes derived from ClC-3-deficient mice similarly underwent apoptosis after exposure to staurosporine; moreover, apoptosis was prevented by application of DIDS or NPPB. Thus, we conclude that in cardiomyocytes, apoptosis is critically dependent on operation not of Cl-/HCO3- exchangers but of Cl- channels which are distinct from ClC-3.

Animals↗
PubMed1991

Biologically active constituents of Melaleuca leucadendron: inhibitors of induced histamine release from rat mast cells.

Chloroform and methanol extracts of the fruits of Melaleuca leucadendron strongly inhibited histamine release from rat mast cells induced by compound 48/80 or concanavalin A. Ursolic acid, a triterpene, was the most active compound contained in the chloroform extract and two stilbenes, piceatannol and oxyresveratrol, were isolated as active compounds from the methanol extract. Several other stilbenes and related compounds were examined to obtain information on the structure activity relationships of stilbenes.

Animals↗
PubMed1989

The low reactivity of 5H-dibenzo[a, d]cycloheptene 10,11-oxide in microsomal epoxide hydrolase catalysed hydration.

1. The rate of hydration of 5H-dibenzo[a, d]cycloheptene 10,11-oxide catalysed by rabbit liver microsomal epoxide hydrolase has been compared with that of the acyclic analogue cis-stilbene oxide. The latter was shown to be a much better substrate for the enzyme than the former epoxide. 2. The kinetic parameters for the hydration of 5H-dibenzo[a,d]cycloheptene 10,11-oxide and cis-stilbene oxide have been determined using a rabbit liver microsomal preparation at 37 degrees C and pH 7.4. The much slower hydration of the former is due to a much lower Vs and not to a higher Km relative to the latter epoxide. 3. 5H-Dibenzo[a,d]cycloheptene 10,11-oxide inhibited the hydration of cis-stilbene oxide by rabbit liver microsomal epoxide hydrolase.

Animals↗
PubMed1988

Transmembrane chloride flux is required for target cell lysis but not for Golgi reorientation in cloned cytolytic effector cells. Golgi reorientation, N alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester serine esterase release, and delivery of the lethal hit are separable events in target cell lysis.

Cell-mediated cytotoxicity can be inhibited by the replacement of chloride with ions that are incapable of passing through chloride channels or by the presence of stilbene disulfonate derivatives known to interfere with chloride flux. We show that the stilbene disulfonate (4,4-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS) inhibits lysis of YAC-1 targets by the cloned cell line NKB61A2. Inhibition of lysis occurs on the level of the effector cell inasmuch as preincubation of effectors but not of targets interferes with subsequent lysis. Moreover, inhibition of chloride flux in the target does not interfere with target cell lysis by cytotoxic granules isolated from killer cells. Target cell binding takes place in the presence of DIDS or absence of external chloride, suggesting that events that follow target cell binding require chloride flux. We show that reorientation of the Golgi apparatus, which occurs subsequent to target cell binding in the effector cell, occurs under conditions that interfere with chloride flux. It is therefore suggested that events in the effector cell taking place subsequent to the Golgi apparatus reorientation reaction are inhibited and that delivery of the lethal hit is a stimulus-induced secretory event that requires transmembrane chloride flux. Delivery of the lethal hit is shown to be independent of the release of N alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester (BLT) serine esterase, suggesting that cytolytic components and BLT serine esterase are likely packaged in different vesicles.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1984

Measurement and characterization of membrane-bound and soluble epoxide hydrolase activities in resting mononuclear leukocytes from human blood.

Membrane-bound and soluble epoxide hydrolase activities in the mononuclear cell fraction from human blood have been characterized using cis- and trans-stilbene oxides as substrates, respectively. Because of the low activities in these cells, it was necessary to modify assay procedures developed for rat and mouse liver in the following ways: (a) the substrates were relatively highly labeled (2 Ci/mmol) and carefully purified; (b) the incubation time was extended to 45 to 60 min, during which period the activities were linear; (c) as many as 6 million cells were used for a single assay, which was also within the linear range of the procedure. The membrane-bound epoxide hydrolase characterized in this manner has an apparent Vmax of 7.26 pmol product formed per min per 10(7) cells and an apparent Km of 9.96 microM. The pH optimum was observed to be around 9.8. The dependence of this activity on temperature showed its optimum at 40 degrees. The soluble epoxide hydrolase activity has an apparent Vmax of about 8.26 pmol product formed per min per 10(7) cells, an apparent Km of 1.63 microM, a pH optimum of 6.2 to 6.8, and a temperature optimum at 60 degrees. Using these techniques, these activities have also been determined in other blood components, i.e., lymphocytes, monocytes, granulocytes, erythrocytes, platelets, and plasma. Lymphocytes account for most of the epoxide hydrolase activity towards cis-stilbene oxide, and all of the activity towards trans-stilbene oxide is in the human mononuclear cell fractions. Different substances known to affect rodent epoxide hydrolases were tested for their effects on the human mononuclear blood cell activities. Interestingly, 1,1,1-trichloropropane 2,3-epoxide, a potent inhibitor of liver microsomal epoxide hydrolase in different species including rat, mouse, and human, had little or no effect on the membrane-bound activity measured here. However, cyclohexene oxide inhibits this membrane-bound activity 60%. The soluble epoxide hydrolase is inhibited to 90% of control levels by chalcone epoxide. The membrane-bound and soluble epoxide hydrolase activities determined in 27 subjects varied from 8.2 to 18.5 and from 3.5 to 17.0 pmol product formed per min per 10(7) cells, respectively. The mean coefficient of intraindividual variation, determined with three subjects measured four times each over the course of 18 days, was approximately 10% for both enzyme activities.

Blood Platelets↗
PubMed1991

Localization and stoichiometry of electrogenic sodium bicarbonate cotransport in retinal glial cells.

An electrogenic Na+/HCO3- cotransport system was identified and characterized in freshly dissociated salamander Müller (glial) cells. Under voltage-clamp, these cells generated an outward current when external HCO3- concentration [( HCO3-]o) was raised. This current was Na(+)-dependent, Cl(-)-independent, and was blocked by the stilbenes 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate (DIDS) and 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS), and by harmaline, demonstrating that the current was generated by a Na+/HCO3- cotransport system. Substantially larger currents were evoked when [HCO3-]o was raised at the Müller cell endfoot as compared to other cell regions, indicating that cotransporter sites are localized preferentially to the endfoot. The reversal potential of the current, which varied as a function of HCO3- and Na+ transmembrane gradients, indicated that the cotransporter has a HCO3-:Na+ stoichiometry of 3:1.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2004

Liquid chromatography/tandem mass spectrometry of unusual phenols from Yucca schidigera bark: comparison with other analytical techniques.

Qualitative and quantitative analyses of phenolic compounds are of interest for both medicinal and food plants. In the present work, the phenolic fraction from Yucca schidigera, a plant bearing the GRAS (Generally Recognized as Safe) label approved by the US Food and Drug Administration, was studied. Crude extracts of Y. schidigera bark were investigated by liquid chromatography/UV spectrophotometry with diode-array detection, liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS), in order to develop and optimize simple and rapid techniques to determine both stilbenes and yuccaols for the purposes of quality control of collected material. With optimal LC and MS conditions, stilbenes and yuccaols were quantified with all the proposed methods and the results were compared. Sensitivity was evaluated and the results indicated that MS/MS detection in the multiple reaction monitoring mode is easily applicable to this plant and allows the rapid and direct identification and quantification of these peculiar compounds in crude plant extracts.

Chromatography, Liquid↗
PubMed2002

A fluorescent-photochrome method for the quantitative characterization of solid phase antibody orientation.

A fluorescent-photochrome method of quantifying the orientation and surface density of solid phase antibodies is described. The method is based on measurements of quenching and rates of cis-trans photoisomerization and photodestruction of a stilbene-labeled hapten by a quencher in solution. These experimental parameters enable a quantitative description of the order of binding sites of antibodies immobilized on a surface and can be used to characterize the microviscosity and steric hindrance in the vicinity of the binding site. Furthermore, a theoretical method for the determination of the depth of immersion of the fluorescent label in a two-phase system was developed. The model exploits the concept of dynamic interactions and is based on the empirical dependence of parameters of static exchange interactions on distances between exchangeable centers. In the present work, anti-dinitrophenyl (DNP) antibodies and stilbene-labeled DNP were used to investigate three different protein immobilization methods: physical adsorption, covalent binding, and the Langmuir-Blodgett technique.

Adsorption↗
PubMed2005

Resveratrol glucoside (Piceid) synthesis in seeds of transgenic oilseed rape (Brassica napus L.).

Resveratrol is a phytoalexin produced in various plants like wine, peanut or pine in response to fungal infection or UV irradiation, but it is absent in members of the Brassicaceae. Moreover, resveratrol and its glucoside (piceid) are considered to have beneficial effects on human health, known to reduce heart disease, arteriosclerosis and cancer mortality. Therefore, the introduction of the gene encoding stilbene synthase for resveratrol production in rapeseed is a tempting approach to improve the quality of rapeseed products. The stilbene synthase gene isolated from grapevine (Vitis vinifera L.) was cloned under control of the seed-specific napin promotor and introduced into rapeseed (Brassica napus L.) by Agrobacterium-mediated co-transformation together with a ds-RNA-interference construct deduced from the sequence of the key enzyme for sinapate ester biosynthesis, UDP-glucose:sinapate glucosyltransferase (BnSGT1), assuming that the suppression of the sinapate ester biosynthesis may increase the resveratrol production in seeds through the increased availability of the precursor 4-coumarate. Resveratrol glucoside (piceid) was produced at levels up to 361 microg/g in the seeds of the primary transformants. This value exceeded by far piceid amounts reported from B. napus expressing VST1 in the wild type sinapine background. There was no significant difference in other important agronomic traits, like oil, protein, fatty acid and glucosinolate content in comparison to the control plants. In the third seed generation, up to 616 microg/g piceid was found in the seeds of a homozygous T3-plant with a single transgene copy integrated. The sinapate ester content in this homozygous T3-plant was reduced from 7.43 to 2.40 mg/g. These results demonstrate how the creation of a novel metabolic sink could divert the synthesis towards the production of piceid rather than sinapate ester, thereby increasing the value of oilseed products.

Acyltransferases↗
PubMed2001

Differential response of immature rat uterine tissue to ethinylestradiol and the red wine constituent resveratrol.

The stilbene derivative resveratrol (RES) is a phytoalexin of grapes, peanuts and other fruits. It is structurally related to stilbene estrogens and an estrogenic potential of RES has recently been demonstrated in a number of in vitro studies. In this investigation, the uterotrophic responses of immature Wistar rats to subcutaneous administration of RES (18, 58, and 575 mg/ kg) and the reference estrogen ethinylestradiol (EE2; 0.3, 1, 3, 30 microg/kg) on three consecutive days were determined. Uterine weight, histopathological changes, immunohistochemical expression of nuclear estrogen receptor-alpha (ERalpha) and progesterone receptor (PR) protein, gene expression of ERalpha and PR at the messenger ribonucleic acid (mRNA) level and peroxidase induction were examined. EE2 dose dependently increased uterine weight, enlarged the uterine lumen and induced hypertrophy of epithelial, stromal and myometrial cells. Expression of ERalpha protein in epithelial, stromal and myometrial nuclei and of PR protein in epithelial nuclei was reduced in EE2-treated rats, while PR protein in stromal and myometrial nuclei was increased in a dose-dependent manner. EE2 increased messenger ribonucleic acid (mRNA) levels of uterine PR and induced peroxidase activity. In contrast, RES rather mildly decreased uterine weight, while histology did not reveal differences between controls and RES-treated rats. Expression of nuclear ERalpha protein was dose dependently decreased in epithelial, stromal and myometrial cells of RES-treated rats, while nuclear PR protein content was similar in controls and RES-treated rats. Following administration of RES, a trend toward reduced levels of ERalpha and PR mRNA was found, while no peroxidase induction occurred. Plasma levels of RES, 45 min after the administration of a single subcutaneous dose of 500 mg/kg, were in the range 1-2 microM. In summary, an estrogenic potential of RES could not be substantiated in this in vivo study, although the most effective route of administration and extremely high doses were used and plasma levels were in the range reported to be effective in vitro. Whether other pharmacological properties of RES could mediate the observed changes in RES-treated animals is discussed.

Animals↗
PubMed1998

Fungitoxicity of chemical analogs with heartwood toxins.

Trans-stilbene and tropolone as chemical analogs with naturally occurring fungitoxic heartwood compounds were studied with respect to their fungitoxic potency. While stilbene showed no fungitoxic activity towards the fungi Aureobasidium pullulans var. melanogenum, Penicillium glabrum, and Trichoderma harzianum in the concentrations tested, the minimal inhibiting concentration of tropolone was 10(-3) M for Penicillium glabrum and Trichoderma harzianum, and 10(-5) M for Aureobasidium pullulans var. melanogenum. In all cases, the effect of tropolone was a fungistatic one. Using chemical analogs for assessing the chemical basis of the fungitoxicity of tropolone, this substance proved to be the only compound tested which possesses fungitoxic properties.

Fungi↗
PubMed2001

Diverse chalcone synthase superfamily enzymes from the most primitive vascular plant, Psilotum nudum.

Psilotum nudum Griseb is a pteridophyte and belongs to the single family (Psilotaceae) of the division, Psilophyta. Being the only living species of a once populated division, P. nudum is the most primitive vascular plant. Chalcone synthase (CHS; EC 2.3.1.74) superfamily enzymes are responsible for biosyntheses of diverse secondary metabolites, including flavonoids and stilbenes. Using a reverse transcription-polymerase chain reaction strategy, four CHS-superfamily enzymes (PnJ, PnI, PnL and PnP) were cloned from P. nudum, and heterologously expressed in Escherichia coli. These four enzymes of 396-406 amino acids showed sequence identity of > 50% among themselves and to other higher-plant CHS-superfamily enzymes. PnJ and PnP preferred p-coumaroyl-CoA and isovaleryl-CoA respectively, as starter CoA and catalyzed CHS-type ring formation, indicating that they are CHS and phlorisovalerophenone synthase, respectively. On the other hand, PnI and PnL preferred cinnamoyl-CoA as starter CoA and catalyzed stilbene synthase-type cyclization and thus were determined to be pinosylvin synthases (EC 2.3.1.146). In addition, PnE, which uniquely contains a glutamine in place of otherwise strictly conserved histidine, had no apparent in vitro catalytic activity. Phylogenetic analysis indicated that these P. nudum clones form a separate cluster together with Equisetum arvense CHS. This cluster of pteridophytes is located next to the cluster formed by pine (gymnosperm) enzymes, in agreement with their evolutionary relationships. Psilotum nudum represents a plant with the most diverse CHS-superfamily enzymes and this ability to diverge may have provided a survival edge during evolution.

Acyltransferases↗
PubMed2005

Synthesis and biodistribution of an 18F-labelled resveratrol derivative for small animal positron emission tomography.

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a naturally occurring phytoalexin and polyphenol existing in grapes and various other plants, and one of the best known 'nutriceuticals'. It shows a multiplicity of beneficial biological effects, particularly, by attenuating atherogenic, inflammatory, and carcinogenic processes. However, despite convincing evidence from experimental and clinical studies, data concerning the role of resveratrol and other members of the large polyphenols family for human health is still a matter of debate. One reason for this is the lack of suitable sensitive and specific methods, which would allow direct assessment of biodistribution, biokinetics, and the metabolic fate of these compounds in vivo. The unique features of positron emission tomography (PET) as a non-invasive in vivo imaging methodology in combination with suitable PET radiotracers have great promise to assess quantitative information on physiological effects of polyphenols in vivo. Herein we describe the radiosynthesis of an (18)F-labelled resveratrol derivative, 3,5-dihydroxy-4'-[(18)F]fluoro-trans-stilbene ([(18)F]-1), using the Horner-Wadsworth-Emmons reaction as a novel radiolabelling technique in PET radiochemistry for subsequent functional imaging of polyphenol metabolism in vivo. In a typical "three-step/one-pot" reaction, (18)F-labelled resveratrol derivative [(18)F]-1 could be synthesized within 120-130 min including HPLC separation at a specific radioactivity of about 90 GBq/mumol. The radiochemical yield was about 9% (decay-corrected) related to [(18)F]fluoride and the radiochemical purity exceeded 97%. First radiopharmacological evaluation included measurement of biodistribution ex vivo and positron emission tomography (PET) studies in vivo after intravenous application of [(18)F]-1 in male Wistar rats using a dedicated small animal PET camera with very high spatial resolution. Concordantly with data on bioavailability and metabolism of native resveratrol from the literature, these investigations revealed an extensive uptake and metabolism in the liver and kidney, respectively, of [(18)F]-1. This study represents the first investigation of polyphenols in vivo by means of PET.

Animals↗
PubMed1986

Comparison of crude and affinity purified cytosolic epoxide hydrolases from hepatic tissue of control and clofibrate-fed mice.

An affinity purification procedure was developed for the cytosolic epoxide hydrolase based upon the selective binding of the enzyme to immobilized methoxycitronellyl thiol. Several elution systems were examined, but the most successful system employed selective elution with a chalcone oxide. This affinity system allowed the purification of the cytosolic epoxide hydrolase activity from livers of both control and clofibrate-fed mice. A variety of biochemical techniques including pH dependence, substrate preference, kinetics, inhibition, amino acid analysis, peptide mapping, Western blotting, analytical isoelectric focusing, and gel permeation chromatography failed to distinguish between the enzymes purified from control and clofibrate-fed animals. The quantitative removal of the cytosolic epoxide hydrolase acting on trans-stilbene oxide from 100,000g supernatants, allowed analysis of remaining activities acting differentially on cis-stilbene oxide and benzo[a]pyrene 4,5-oxide. Such analysis indicated the existence of a novel epoxide hydrolase activity in the cytosol of mouse liver preparations.

Animals↗
PubMed1982

Differential induction of rat liver microsomal UDP-glucuronosyltransferase activites by various inducing agents.

The selectivity of various inducers of UDP-glucuronosyltransferase was investigated in rat liver microsomes and compared with their effect on monooxygenase reactions. (1) Similar to 3-methyl-cholanthrene beta-naphthoflavone selectively stimulated the glucuronidation of 1-naphthol and 4-methylumbelliferone (GT1 substrates). (2) In contrast, DDT preferentially enhanced the glucuronidation of morphine, 4-hydroxybiphenyl (GT2 substrates) and bilirubin, similar to phenobarbital. (3) Colfibric acid and bezafibrate selectively enhanced bilirubin glucuronidation without affecting GT1 and GT2 reactions. (4) Similar to ethoxyquin and Aroclor 1254, trans-stilbene oxide enhanced both GT1 and GT2 activities but not bilirubin glucuronidation. (5) In contrast to 3-methylcholanthrene-type inducers which induce both cytochrome P-450MC and GT1, probably through a common receptor protein, ethoxyquin and trans-stilbene oxide markedly induced GT1 reactions without affecting benzo[a]pyrene monooxygenase.

Animals↗
PubMed1989

Microsomal and cytosolic epoxide hydrolase and glutathione S-transferase activities in the gill, liver, and kidney of the rainbow trout, Salmo gairdneri. Baseline levels and optimization of assay conditions.

Microsomal and cytosolic epoxide hydrolase (mEH and cEH respectively) and glutathione S-transferase (GST) activities were measured in the liver, kidney, and gills of rainbow trout. Assays were optimized for time, pH, and temperature, using trans-stilbene oxide (TSO) and cis-stilbene oxide (CSO) as substrates for cEH and mEH, respectively. Optimal pH values for mEH, cEH, and GST were similar to mammalian values (i.e. 8.5, 7.5, and 9). Temperature optima differed between tissues and cell fractions. Specific activity of cEH-TSO was 3-14 times greater than mEH-CSO for all three tissues, and 8-60 times greater on a tissue weight basis. Liver and, to a lesser extent, kidney mEH were active against benzo[a]pyrene 4,5-oxide, whereas gill mEH was not active against this substrate. Liver cytosolic GST was active against CSO and 1-chloro-2,4-dinitrobenzene (CDNB) but not TSO, whereas gill and kidney cytosolic GST were active only against CDNB. Liver and kidney microsomal GST were active against CDNB, but no activity was found in gill microsomes. The results are discussed in relation to possible endogenous substrates and uninduced xenobiotic metabolizing capacities of different trout tissues.

Animals↗