TY  - JOUR
AB  - The aldo-keto reductase (AKR) superfamily comprises NAD(P) H-dependent enzymes that catalyze the reduction of a variety of carbonyl compounds. AKRs are classified in families and subfamilies. Humans exhibit three members of the AKR1B subfamily: AKR1B1 (aldose reductase, participates in diabetes complications), AKR1B10 (overexpressed in several cancer types), and the recently described AKR1B15. AKR1B10 and AKR1B15 share 92% sequence identity, as well as the capability of being active towards retinaldehyde. However, AKR1B10 and AKR1B15 exhibit strong differences in substrate specificity and inhibitor selectivity. Remarkably, their substrate-binding sites are the most divergent parts between them. Out of 27 residue substitutions, six are changes to Phe residues in AKR1B15. To investigate the participation of these structural changes, especially the Phe substitutions, in the functional features of each enzyme, we prepared two AKR1B10 mutants. The AKR1B10 m mutant carries a segment of six AKR1B15 residues (299-304, including three Phe residues) in the respective AKR1B10 region. An additional substitution (Val48Phe) was incorporated in the second mutant, AKR1B10mF48. This resulted in structures with smaller and more hydrophobic binding pockets, more similar to that of AKR1B15. In general, the AKR1B10 mutants mirrored well the specific functional features of AKR1B15, i.e., the different preferences towards the retinaldehyde isomers, the much higher activity with steroids and ketones, and the unique behavior with inhibitors. It can be concluded that the Phe residues of loop C (299-304) contouring the substrate-binding site, in addition to Phe at position 48, strongly contribute to a narrower and more hydrophobic site in AKR1B15, which would account for its functional uniqueness. In addition, we have investigated the AKR1B10 and AKR1B15 activity toward steroids. While AKR1B10 only exhibits residual activity, AKR1B15 is an efficient 17-ketosteroid reductase. Finally, the functional role of AKR1B15 in steroid and retinaldehyde metabolism is discussed.
AU  - Giménez-Dejoz, J.*
AU  - Weber, S.
AU  - Fernández-Pardo, A.*
AU  - Möller, G.
AU  - Adamski, J.
AU  - Porté, S.*
AU  - Parés, X.*
AU  - Farrés, J.*
C1  - 55946
C2  - 46714
CY  - Elsevier House, Brookvale Plaza, East Park Shannon, Co, Clare, 00000, Ireland
SP  - 186-194
TI  - Engineering aldo-keto reductase 1B10 to mimic the distinct 1B15 topology and specificity towards inhibitors and substrates, including retinoids and steroids.
JO  - Chem. Biol. Interact.
VL  - 307
PB  - Elsevier Ireland Ltd
PY  - 2019
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - Aldo-keto reductases (AKRs) are distributed in three families and multiple subfamilies in mammals. The mouse Akr1b3 gene is clearly orthologous to human AKR1B1, both coding for aldose reductase, and their gene products show similar tissue distribution, regulation by osmotic stress and kinetic properties. In contrast, no unambiguous orthologs of human AKR1B10 and AKR1B15.1 have been identified in rodents. Although two more AKRs, AKR1B7 and AKR1B8, have been identified and characterized in mouse, none of them seems to exhibit properties similar to the human AKRs. Recently, a novel mouse AKR gene, Akr1b16, was annotated and the respective gene product, AKR1B16 (sharing 83% and 80% amino acid sequence identity with AKR1B10 and AKR1B15.1, respectively), was expressed as insoluble and inactive protein in a bacterial expression system. Here we describe the expression and purification of a soluble and enzymatically active AKR1B16 from E. coli using three chaperone systems. A structural model of AKR1B16 allowed the estimation of its active-site pocket volume, which was much wider (402 Å3) than those of AKR1B10 (279 Å3) and AKR1B15.1 (60 Å3). AKR1B16 reduced aliphatic and aromatic carbonyl compounds, using NADPH as a cofactor, with moderate or low activity (highest kcat values around 5 min-1). The best substrate for the enzyme was pyridine-3-aldehyde. AKR1B16 showed poor inhibition with classical AKR inhibitors, tolrestat being the most potent. Kinetics and inhibition properties resemble those of rat AKR1B17 but differ from those of the human enzymes. In addition, AKR1B16 catalyzed the oxidation of 17β-hydroxysteroids in a NADP+-dependent manner. These results, together with a phylogenetic analysis, suggest that mouse AKR1B16 is an ortholog of rat AKR1B17, but not of human AKR1B10 or AKR1B15.1. These human enzymes have no counterpart in the murine species, which is evidenced by forming a separate cluster in the phylogenetic tree and by their unique activity with retinaldehyde.
AU  - Giménez-Dejoz, J.*
AU  - Weber, S.
AU  - Barski, O.A.*
AU  - Möller, G.
AU  - Adamski, J.
AU  - Parés, X.*
AU  - Porté, S.*
AU  - Farrés, J.*
C1  - 50757
C2  - 42517
CY  - Clare
SP  - 182-193
TI  - Characterization of AKR1B16, a novel mouse aldo-keto reductase.
JO  - Chem. Biol. Interact.
VL  - 276
PB  - Elsevier Ireland Ltd
PY  - 2017
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - Evidence in the current literature suggests that expression and activity of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), a key regulatory enzyme in glucocorticoid metabolism, is elevated in the liver and reduced in visceral adipose tissue and skeletal muscle following caloric restriction (CR). In order to investigate the influence of CR on 11β-HSD1 in more detail, we assessed expression and activity of 11β-HSD1 in several tissues in two independent CR and re-feeding animal models. Levels and activity of 11β-HSD1 after CR and re-feeding were measured [mouse liver and pig liver, pig visceral adipose tissue and pig skeletal muscle] using semi-quantitative RT-PCR, Western Blot analysis, and HPLC. After CR, no significant difference on mRNA levels was detected in mouse liver. But 11β-HSD1 mRNA expression was upregulated after subsequent re-feeding. In contrast, 11β-HSD1 protein expression after CR was significantly up-regulated, while no difference was detected after re-feeding. Interestingly, upregulation of protein after CR (1.4-fold) was lower than the increase in enzymatic activity (2.6-fold). Furthermore, while no difference was observed in protein levels after two weeks re-feeding, 11β-HSD1 activity increased 2.5-fold. In pig tissues neither 11β-HSD1 mRNA levels, protein expression or enzyme activity were influenced after CR and re-feeding. Overall, the results demonstrate species-dependent differences in regulation of 11β-HSD1 following CR and suggest the presence of an additional regulation step for 11β-HSD1 activity in mouse liver.
AU  - Loerz, C.*
AU  - Staab-Weijnitz, C.A.
AU  - Huebbe, P.*
AU  - Giller, K.*
AU  - Metges, C.*
AU  - Rimbach, G.*
AU  - Maser, E.*
C1  - 50623
C2  - 42653
CY  - Clare
SP  - 95-104
TI  - Regulation of 11β-hydroxysteroid dehydrogenase type 1 following caloric restriction and re-feeding is species dependent.
JO  - Chem. Biol. Interact.
VL  - 276
PB  - Elsevier Ireland Ltd
PY  - 2017
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - The olefin ethylene is a ubiquitously found gas. It originates predominantly from plants, combustion processes and industrial sources. In mammals, inhaled ethylene is metabolized by cytochrome P450-dependent monooxygenases, particularly by cytochrome P450 2E1, to ethylene oxide, an epoxide that directly alkylates proteins and DNA. Ethylene oxide was mutagenic in vitro and in vivo in insects and mammals and carcinogenic in rats and mice. A physiological toxicokinetic model is a most useful tool for estimating the ethylene oxide burden in ethylene-exposed rodents and humans. The only published physiological toxicokinetic model for ethylene and metabolically produced ethylene oxide is discussed. Additionally, existing data required for the development of a future model and for testing its predictive accuracy are reviewed and extended by new gas uptake studies with ethylene and ethylene oxide in B6C3F1 mice and with ethylene in F344 rats.
AU  - Filser, J.G.
AU  - Artati, A.
AU  - Li, Q.
AU  - Pütz, C.
AU  - Semder, B.
AU  - Klein, D.
AU  - Kessler, W.
C1  - 44393
C2  - 36822
SP  - 76-86
TI  - Novel and existing data for a future physiological toxicokinetic model of ethylene and its metabolite ethylene oxide in mouse, rat and human.
JO  - Chem. Biol. Interact.
VL  - 241
PY  - 2015
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - Endometrial cancer is the most frequently diagnosed gynecological malignancy. It is associated with prolonged exposure to estrogens that is unopposed by progesterone, whereby enhanced metabolism of progesterone may decrease its protective effects, as it can deprive progesterone receptors of their active ligand. Furthermore, the 5α-pregnane metabolites formed can stimulate proliferation and may thus contribute to carcinogenesis. The aims of our study were to: 1) identify and quantify progesterone metabolites formed in the HEC-1A and Ishikawa model cell lines of endometrial cancer; and 2) pinpoint the enzymes involved in progesterone metabolism, and delineate their roles. Progesterone metabolism studies combined with liquid chromatography-tandem mass spectrometry enabled identification and quantification of the metabolites formed in these cells. Further quantitative PCR analysis and small-interfering-RNA-mediated gene silencing identified individual progesterone metabolizing enzymes and their relevant roles. In Ishikawa and HEC-1A cells, progesterone was metabolized mainly to 20α-hydroxy-pregn-4-ene-3-one, 20α-hydroxy-5α-pregnane-3-one, and 5α-pregnane-3α/β,20α-diol. The major difference between these cell lines was rate of progesterone metabolism, which was faster in HEC-1A cells. In the Ishikawa and HEC-1A cells, expression of AKR1C2 was 110-fold and 6,800-fold greater, respectively, than expression of AKR1C1, which suggests that 20-ketosteroid reduction of 5α-pregnanes and 4-pregnenes is catalyzed mainly by AKR1C2. AKR1C1/AKR1C2 gene silencing showed decreased progesterone metabolism in both cell lines, thus further supporting the significant role of AKR1C2. SRD5A1 was also expressed in these cells, and its silencing confirmed that 5α-reduction is catalyzed by 5α-reductase type 1. Silencing of SRD5A1 also had the most pronounced effects, with decreased rate of progesterone metabolism, and consequently higher concentrations of unmetabolized progesterone. Our data confirm that in model cell lines of endometrial cancer, AKR1C2 and SRD5A1 have crucial roles in progesterone metabolism, and may represent novel targets for treatment.
AU  - Sinreih, M.*
AU  - Anko, M.*
AU  - Zukunft, S.
AU  - Adamski, J.
AU  - Lanisnik Rizner, T.*
C1  - 42883
C2  - 35740
CY  - Clare
SP  - 297-308
TI  - Important roles of the AKR1C2 and SRD5A1 enzymes in progesterone metabolism in endometrial cancer model cell lines.
JO  - Chem. Biol. Interact.
VL  - 234
PB  - Elsevier Ireland Ltd
PY  - 2014
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - In the present study V79 Chinese hamster cells were genetically engineered for stable expression of the cytochromes P450 1A1, 1A2, 1B1, and 2E1 from man and mouse to investigate species-specific differences in the regioselective metabolism and toxicity of phenanthrene (Phe), the simplest polycyclic aromatic hydrocarbon (PAN) forming a bay-region. Phe is present in various environmental samples and serves as a model substrate for PAH exposure in human biomonitoring studies. For this reason we explored metabolite profiles and metabolite-dependent cytotoxic activities in vitro. The total turnover of CYP-mediated transformation of Phe was as follows: human CYP1B1>CYP1A1>CYP1A2 >> CYP2E1, and for mouse CYP1A2 >> CYP2E1>CYP1A1. Striking species differences were seen as mouse CYP1B1 did not activate Phe at all, but human CYP1B1 exhibited a significant metabolic turnover comparable to CYP1A1 and CYP1A2. In vivo studies monitoring the whole blood Phe elimination in CYP1A2 knockout and wildtype mice after oral administration confirmed involvement of CYP1A2 in the bioactivation of Phe, but other processes must contribute also. Our data suggest that in humans not only CYP1A2 expressed solely in the liver plays a crucial role in Phe metabolism, but also constitutively expressed extrahepatic CYP1B1 in tissues such as lung, kidney or intestine. This finding will substantially improve the validity of human biomonitoring studies using individual Phe metabolites for the assessment of PAH exposure.
AU  - Schober, W.
AU  - Pusch, G.
AU  - Oeder, S.
AU  - Reindl, H.
AU  - Behrendt, H.
AU  - Buters, J.T.M.
C1  - 536
C2  - 27901
SP  - 57-66
TI  - Metabolic activation of phenanthrene by human and mouse cytochromes P450 and pharmacokinetics in CYP1A2 knockout mice.
JO  - Chem. Biol. Interact.
VL  - 183
IS  - 1
PB  - Elsevier Ireland Ltd.
PY  - 2010
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - Hydroxysteroid dehydrogenase like 1 protein (HSDL1) is an uncharacterized member of short-chain dehydrogenase/reductase (SDR) protein family. In search for functional assignment of both human and zebrafish HSDL1 we characterized the subcellular localization as well as the tissue distribution and performed a screen for putative substrates of HSDL1 enzymes. Surprisingly, human HSDL1 shows exchange of an amino acid in the active center (Sx(12)FSxxK instead of Sx(12)YSxxK) that is considered critical for catalysis. Native human HSDL1 expressed in cells did not show enzymatic activity with any of the substrates tested. Expression of the point mutation F218Y HSDL1 though, resulted in the detection of weak dehydrogenase activity towards steroid and retinoid substrates. The role of this inactivating mutation is uncertain but was found to be conserved in many other vertebrate species, including zebrafish. Identification of protein interaction partners by yeast two-hybrid system suggests that despite the potential lack of enzymatic activity HSDL1 might retain regulatory functions in the cell.
AU  - Meier, M.
AU  - Tokarz, J.
AU  - Haller, F.
AU  - Mindnich, R.*
AU  - Adamski, J.
C1  - 5081
C2  - 25908
SP  - 197-205
TI  - Human and zebrafish hydroxysteroid dehydrogenase like 1 (HSDL1) proteins are inactive enzymes but conserved among species.
JO  - Chem. Biol. Interact.
VL  - 178
IS  - 1-3
PB  - Elsevier
PY  - 2009
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - Short-chain dehydrogenases/reductases (SDR) constitute one of the largest enzyme superfamilies with presently over 46,000 members. In phylogenetic comparisons, members of this superfamily show early divergence where the majority have only low pairwise sequence identity, although sharing common structural properties. The SDR enzymes are present in virtually all genomes investigated, and in humans over 70 SDR genes have been identified. In humans, these enzymes are involved in the metabolism of a large variety of compounds, including steroid hormones, prostaglandins, retinoids, lipids and xenobiotics. It is now clear that SDRs represent one of the oldest protein families and contribute to essential functions and interactions of all forms of life. As this field continues to grow rapidly, a systematic nomenclature is essential for future annotation and reference purposes. A functional subdivision of the SDR superfamily into at least 200 SDR families based upon hidden Markov models forms a suitable foundation for such a nomenclature system, which we present in this paper using human SDRs as examples.
AU  - Persson, B.*
AU  - Kallberg, Y.*
AU  - Bray, J.E.*
AU  - Bruford, E.*
AU  - Dellaporta, S.L.*
AU  - Favia, A.D.*
AU  - Duarte, R.G.*
AU  - Jörnvall, H.*
AU  - Kavanagh, K.L.*
AU  - Kedishvili, N.*
AU  - Kisiela, M.*
AU  - Maser, E.*
AU  - Mindnich, R.*
AU  - Orchard, S.*
AU  - Penning, T.M.*
AU  - Thornton, J.M.*
AU  - Adamski, J.
AU  - Oppermann, U.*
C1  - 5080
C2  - 25907
SP  - 94-98
TI  - The SDR (short-chain dehydrogenase/reductase and related enzymes) nomenclature initiative.
JO  - Chem. Biol. Interact.
VL  - 178
IS  - 1-3
PB  - Elsevier Ireland Ltd.
PY  - 2008
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - 1,3-Butadiene (BD) was carcinogenic in rodents. This effect is related to reactive metabolites such as 1,2-epoxy-3-butene (EB) and especially 1,2:3,4-diepoxybutane (DEB). A third mutagenic epoxide, 3,4-epoxy-1,2-butanediol (EBD), can be formed from DEB and from 3-butene-1,2-diol (B-diol), the hydrolysis product of EB. In BD exposed rodents, only blood concentrations of EB and DEB have been published. Direct determinations of EBD and B-diol in blood are missing. In order to investigate the BD-dependent blood burden by all of these metabolites, we exposed male B6C3F1 mice and male Sprague-Dawley rats in closed chambers over 6–8 h to constant atmospheric BD concentrations. BD and exhaled EB were measured in chamber atmospheres during the BD exposures. EB blood concentrations were obtained as the product of the atmospheric EB concentration at steady state with the EB blood-to-air partition coefficient. B-diol, EBD, and DEB were determined in blood collected immediately at the end of BD exposures up to 1200 ppm (B-diol, EBD) and 1280 ppm (DEB). Analysis of BD was done by GC/FID, of EB, DEB, and B-diol by GC/MS, and of EBD by LC/MS/MS. EB blood concentrations increased with BD concentrations amounting to 2.6 ?mol/l (rat) and 23.5 ?mol/l (mouse) at 2000 ppm BD and to 4.6 ?mol/l in rats exposed to 10000 ppm BD. DEB (detection limit 0.01 ?mol/l) was found only in blood of mice rising to 3.2 ?mol/l at 1280 ppm BD. B-diol and EBD were quantitatively predominant in both species. B-diol increased in both species with the BD exposure concentration reaching 60 ?mol/l at 1200 ppm BD. EBD reached maximum concentrations of 9.5 ?mol/l at 150 ppm BD (rat) and of 42 ?mol/l at 300 ppm BD (mouse). At higher BD concentrations EBD blood concentrations decreased again. This picture probably results from a competitive inhibition of the EBD producing CYP450 by BD, which occurs in both species.
AU  - Filser, J.G.
AU  - Hutzler, C.*
AU  - Meischner, V.
AU  - Veereshwarayya, V.
AU  - Csanády, G.A.
C1  - 2363
C2  - 24343
SP  - 93-103
TI  - Metabolism of 1,3-butadiene to toxicologically relevant metabolites in single-exposed mice and rats.
JO  - Chem. Biol. Interact.
VL  - 166
IS  - 1-3
PB  - Elsevier
PY  - 2007
SN  - 0009-2797
ER  - 

TY  - JOUR
AU  - Schober, W.
AU  - Luch, A.*
AU  - Soballa, V.J.*
AU  - Raab, G.*
AU  - Stegeman, J.J.*
AU  - Doehmer, J.*
AU  - Jacob, J.*
AU  - Seidel, A.*
C1  - 5352
C2  - 24234
SP  - 37-48
TI  - On the species-specific biotransformation of dibenzo[a,l]pyrene.
JO  - Chem. Biol. Interact.
VL  - 161
PY  - 2006
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - 17β-Hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17β-HSDcl) is a NADPH dependent member of the short-chain dehydrogenase reductase (SDR) superfamily. Recently, we prepared a homology-built structural model of 17β-HSDcl using the known three-dimensional structure of homologous 1,3,8-trihydroxynaphthalene reductase from the fungus Magnaporthe grisea. This model structure directed our studies of structure–function relationship of the fungal 17β-HSD, as one of the model enzymes of the SDR superfamily. In this work, we investigated the significance of individual amino acid residues for coenzyme and substrate specificity. We performed site directed mutagenesis of R28, a basic residue conserved in most NADPH dependent SDR structures; T200, found only in Streptomyceshydrogenans 3α,20β-HSD and Drosophila alcohol dehydrogenases; and H230, a residue corresponding to the substrate specificity important H221 in human 17β-HSD type 1. All recombinant proteins were expressed in Escherichia coli and purified to homogeneity. Kinetic evaluation of individual mutations was performed by analysis of progress curves of interconversions between 4-estrene-3,17-dione and 4-estrene-17β-ol-3-one, in the presence of NADPH and NADP+; according to the Theorell–Chance reaction mechanism. The results demonstrate the role of the selected amino acid residues; R28 seems to interact with the NADPH 2′-phosphate group; T200 may be involved in binding and dissociation of NADPH/NADP+; while H230 and the neighboring A231 appears not to be responsible for substrate specificity of 17β-HSDcl.
AU  - Kristan, K.*
AU  - Rizner, T.L.*
AU  - Stojan, J.*
AU  - Gerber, J.-K.
AU  - Kremmer, E.
AU  - Adamski, J.
C1  - 22221
C2  - 20936
SP  - 493-501
TI  - Significance of individual amino acid residues for coenzyme and substrate specificity of 17ß- hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus.
JO  - Chem. Biol. Interact.
VL  - 143-144
PY  - 2003
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - Isoprene (IP) is ubiquitous in the environment and is used for the production of polymers. It is metabolized in vivo to reactive epoxides, which might cause the tumors observed in IP exposed rodents. Detailed knowledge of the body and tissue burden of inhaled IP and its intermediate epoxides can be gained using a physiological toxicokinetic (PT) model. For this purpose, a PT-model was developed for IP in mouse, rat, and human. Experimentally determined partition coefficients were taken from the literature. Metabolic parameters were obtained from gas-uptake experiments. The measured data could be described by introducing hepatic and extrahepatic metabolism into the model. At exposure concentrations up to 50 ppm, the rate of metabolism at steady-state is 14 times faster in mice and about 8 times faster in rats than in humans (2.5 micromol/h/kg at 50 ppm IP in air). IP does accumulate only barely due to its fast metabolism and its low thermodynamic partition coefficient whole body:air. IP is produced endogenously. This production is negligible in rodents compared to that in humans (0.34 micromol/h/kg). About 90% of IP produced endogenously in humans is metabolized and 10% is exhaled unchanged. The blood concentration of IP in non-exposed humans is predicted to be 9.5 nmol/l. The area under the blood concentration-time curve (AUC) following exposure over 8 h to 10 ppm IP is about 4 times higher than the AUC resulting from the unavoidable endogenous IP over 24 h. A comparison of such AUCs can be used for establishing workplace exposure limits. For estimation of the absolute risk, knowledge of the body burden of the epoxide intermediates of IP is required. Unfortunately, such data are not yet available.
AU  - Csanády, G.A.
AU  - Filser, J.G.
C1  - 23911
C2  - 31390
SP  - 679-685
TI  - Toxicokinetics of inhaled and endogenous isoprene in mice, rats, and humans.
JO  - Chem. Biol. Interact.
VL  - 135-136
PB  - Elsevier
PY  - 2001
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - First-pass metabolism of 1,3-butadiene (BD) leading to 1,2-epoxy-3-butene (EB), 1,2:3,4-diepoxybutane (DEB), 3-butene-1,2-diol (B-diol), 3,4-epoxy-1,2-butanediol (EBD) and crotonaldehyde (CA) was studied quantitatively in the once-through BD perfused liver of mouse and rat by means of an all-glass gas-tight perfusion system. Metabolites were analyzed using gas chromatography equipped with mass selective detection. The perfusate consisted of Krebs-Henseleit buffer (pH 7.4) containing bovine erythrocytes (40%v/v) and BD. The perfusion flow rates through the livers were 3-4 ml/min (mouse) and 17-20 ml/min (rat). The BD concentrations in the liver perfusates were 330 nmol/ml (mouse) and 240 nmol/ml (rat) being high enough to reach almost saturation of BD metabolism. The mean rates of BD transformation were about 0.014 and 0.055 mmol/h per liver of a mouse and a rat, respectively, being similar to the values expected from in-vivo measurements. There were marked species differences in the formation of BD metabolites. In the effluent of mouse livers, all three epoxides (EB: 9.4 nmol/ml; DEB: 0.06 nmol/ml; EBD: 0.07 nmol/ml) and B-diol (8.2 nmol/ml) were detected. In the perfusate leaving naïve rat livers, only EB and B-diol were found. In that of rat liver, EB concentration was 8.5 times smaller than in that of mouse liver, whereas B-diol concentrations were similar in the effluent liver perfusate of both species. CA was below the limit of its detection (60 nmol/l) in the liver perfusate of mice and of naïve rats. Of BD metabolized, the sum of the metabolites investigated in the effluent amounted to only 30% (mouse) and 20% (rat). In first experiments with rat liver, glutathione (GSH) was depleted by pretreating the animals with diethylmaleate. With the exception of EBD (not quantifiable due to an interfering peak), all other metabolites including CA were found in the effluent perfusate summing up to about 70 and 100% of BD metabolized, which indicates the quantitative importance of the GSH dependent metabolism. In summary, the results demonstrate the relevance of an intrahepatic first-pass metabolism for metabolic intermediates of BD, which undergo further transformation immediately after their production in the liver before leaving this organ. Hitherto, the occurrence of this first-pass metabolism was only hypothesized. The findings will help to explain the drastic species difference between mice and rats in the carcinogenic potency of BD.
AU  - Filser, J.G.
AU  - Faller, T.H.
AU  - Bhowmik, S.
AU  - Schuster, A.
AU  - Kessler, W.
AU  - Pütz, C.
AU  - Csanády, G.A.
C1  - 23893
C2  - 31393
SP  - 249-265
TI  - First-pass metabolism of 1,3-butadiene in once-through perfused livers of rats and mice.
JO  - Chem. Biol. Interact.
VL  - 135-136
PB  - Elsevier
PY  - 2001
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - With regard to the stability of the NO. radical as a chemical entity, it is without doubt able to serve as an intra- as well as an intercellular messenger. The radical O2-., in contrast, does not seem to be suited to far-range signalling in the vascular system. Its short chemical half-life, which is limited by the presence of various reactive blood constituents to below 50 ms, results in a free diffusion path length of less than 40 microns, i.e. only the distance between just a few cells. While accelerated 'downstream' transport by arterial blood may help to extend the action sphere, there is no possibility for O2-. to serve as a signal in an upstream direction. The estimates presented, however, do not invalidate arguments for a possible role of superoxide anions in intra- or pericellular signalling phenomena. Cross-talk between NO.- and O2-.-dependent signal routes, e.g. by peroxynitrite formation, is unlikely to be a relevant process under the conditions which prevail in the vascular system.
AU  - Saran, M.
AU  - Bors, W.
C1  - 20596
C2  - 13806
SP  - 35-45
TI  - Signalling by O2- and NO: How far can either radical, or any specific reaction product, transmit a message under in vivo conditions.
JO  - Chem. Biol. Interact.
VL  - 90
IS  - 1
PY  - 1993
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - The synergistic effect of dexamethasone (DEX) and polycyclic aromatic hydrocarbons on the induction of cytochrome P450IA1 (P450IA1) was examined in H4IIEC3/T Reuber hepatoma cells. P450IA1 activity was determined by the hydroxylation of benzo[a]pyrene (AHH) and deethylation of 7-ethoxy-resorufin (EROD). The amount of Ah receptors, i.e. the specific cytosolic binding protein of 3-methylcholanthrene or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in H4IIEC3/T cells was characterized and quantitated by high performance gel filtration. Benz[a]anthracene and TCDD induced AHH and EROD activities, respectively, about 20-fold within 4 h. The increase was about 100-fold when cells were pretreated with DEX. The glucocorticoid alone induced P450IA1 activities 3-4-fold. DEX elicited half maximum AHH induction at a concentration of 20 nM in the presence or absence of benz[a]anthracene. Maximal potentiation of AHH induction required treatment with DEX for at least 32 h prior to the exposure to benz[a]anthracene. Treatment of H4IIEC3/T cells with DEX for 20 h caused a 2-3-fold increase in the amount of Ah receptor. The results suggest that the synergistic effect of DEX and polycyclic aromatic hydrocarbons on P450IA1 induction involves a time-consuming process which may consist of the synthesis or modification of a factor, possibly the Ah receptor.
AU  - Wiebel, F.J.
AU  - Cikryt, P.
C1  - 34147
C2  - 35491
SP  - 307-320
TI  - Dexamethasone-mediated potentiation of P450IA1 induction in H4IIEC3/T hepatoma cells is dependent on a time-consuming process and associated with induction of the Ah receptor.
JO  - Chem. Biol. Interact.
VL  - 76
IS  - 3
PY  - 1990
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - The effect of polychlorinated biphenyls, γ-hexachlorocyclohexane and the effect of a combination of these substances on the regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase were investigated. As known from previous investigations polychlorinated biphenyls interfere with the regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in rat liver via enzyme-lipid interaction and at the pretranslational level. In contrast to polychlorinated biphenyls, γ-hexachlorocyclohexane did not alter the lipid status of the microsomal membrane. Thus the location of the 3-hydroxy-3-methylglutaryl coenzyme A reductase, and consequently the catalytic activity of the enzyme was not changed. As with polychlorinated biphenyls, γ-hexachlorocyclohexane interacted with enzyme regulation at the pretranslational level. Northern dot hybridization experiments showed a decrease in the level of m-RNA coding for 3-hydroxy-3-methylglutaryl coenzyme A reductase. The effect of combination of γ-hexachlorocyclohexane and polychlorinated biphenyls was not additive. The γ-hexachlorocyclohexane effect appeared to play a more important role than that of the polychlorinated biphenyls. The results indicate that the combination effects are as important as the effects of the single compounds when making risk assessments for xenobiotics.
AU  - Jenke, H.S.
AU  - Löwel, M.
AU  - Berndt, J.
C1  - 42241
C2  - 36130
SP  - 175-186
TI  - Modes of action and combination effects of polychlorinated biphenyls and γ-hexachlorocyclohexane on the regulation of rat liver 3-hydroxy-3-methylglutaryl coenzyme A reductase.
JO  - Chem. Biol. Interact.
VL  - 65
IS  - 2
PY  - 1988
SN  - 0009-2797
ER  - 

TY  - JOUR
AB  - Interaction of the insecticide 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) with β-receptor binding and adenylate cyclase activity of biological membranes has been studied. Following exposure of cultured Chang liver cells to DDT, maximal binding of the catecholamine antagonist [125I]-iodohydroxybenzylpindol (HYP) to isolated cell membranes was decreased by 30% whereas the dissociation constant remained unchanged. Both basal activity and maximal isoproterenol-stimulated activity of adenylate cyclase were not altered. The isoproterenol concentration required for half-maximal stimulation of the enzyme was increased about 2-fold as was the agonist concentration required for half-maximal displacement of the antagonist HYP at the β-receptor binding site. Thus, coupling efficiency of hormone-stimulated adenylate cyclase activity was not influenced by the presence of DDT in these membranes. The data show that interaction of DDT with the β-receptor adenylate cyclase complex is restricted to the receptor component. Enzyme activity is directly linked to changes of agonist binding at the β-receptor. Interference of DDT with signal transuction via 'fluidization' of membrane lipids has not been detected.
AU  - Buff, K.
AU  - Bründl, A.
AU  - Berndt, J.
C1  - 41049
C2  - 0
SP  - 337-346
TI  - Interaction of the insecticide 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane with the β-receptor adenylate cyclase system in Chang liver cell membranes.
JO  - Chem. Biol. Interact.
VL  - 47
IS  - 3
PY  - 1983
SN  - 0009-2797
ER  - 

TY  - JOUR
AU  - Pöschl, E.
AU  - Buff, K.
AU  - Berndt, J.
C1  - 41074
C2  - 38871
SP  - 369-374
TI  - Effect of DDT on adenylate cyclase activity in rat liver cell membranes.
JO  - Chem. Biol. Interact.
VL  - 39
IS  - 3
PY  - 1982
SN  - 0009-2797
ER  -