@article{VivianiLutzSchlatter1978,
  author    = {Viviani, A. and Lutz, Werner K. and Schlatter, C.},
  title     = {Time course of the induction of aryl hydrocarbon hydroxylase in rat liver nuclei and microsomes by phenobarbital, 3-methylcholanthrene, 2,3,7,8-tetrachloro-dibenzo-p-dioxin, dieldrin and other inducers},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61182},
  year      = {1978},
  abstract  = {Aryl hydrocarbon hydroxylase (AHH) has been measured in male rat Jiver nucJei and microsomes after treatment of adult animals with various inducers for up to 14 days. After daily i.p. injections of 3-methylcholanthrene (MC, 20 mg/kg) the nuclear activity increased to a maximum of 600 per cent of the control activity after 4 days whereas the microsomal activity was 400 per cent of control at the same date. After 12 days, both activities equilibrated at 400 per cent. A similar time course was found after a single i.p. injection of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD, 0.01 mg/kg) with an induction to .500 and 300 per cent for nuclei and microsomes, respectiveJy. after 2 days, and to 400 per cent for both after 12 days. PhenobarbitaJ (PB) was given continuously in the drinking water (I g/1) and induced the microsomal activity to 200 per cent after 8 days and 170 per cent after 14 days. The nuclear activity was only slightly induced to a constant Ievei of 130 per cent between day 8 and 14. Dieldrin did not significantly increase the microsomal activity after daiJy i.p. injections (20 mg/kg), but the nuclear activity raised to 200 per cent after 3 days and levelled down tocontrol valuesafter 12 days. Other inducers tested were benz[a)anthracene (BA), hexachlorobenzene (HCB} and 1,1.1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT). The induction pattern with BA was similar tothat of MC, a modeJ compound for the group of cytochrome P448 inducers. The induction by HCB and DDT resembled that by PB. a typical cytochrome P450 inducer.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{LutzViviantSchlatter1978,
  author    = {Lutz, Werner K. and Viviant, A. and Schlatter, C.},
  title     = {Nonlinear dose-response relationship for the binding of the carcinogen benzo(a)pyrene to rat liver DNA in vivo},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61179},
  year      = {1978},
  abstract  = {Wlth radioactive compound of high specific activity, the binding of carcinogene to DNA can be measured wlth doses that are ineffective ln long-term studies. The binding of tritiated benzo(a )pyrene to liver DNA of adult male rats has been determined 50 hr after a singie l.p. injection of doses between 40 1'9/kg and 4 mg/kg. The doseresponse relationship is linear up to 1 mg/kg, shows a step towards 2 mg/kg, and gives a shallow linear slope above that value. The observed binding ranges from 1.7 to 180 nmoles benzo(a)pyrene per mole DNA phosphate. The nonlinearity could be due to an induction of metabolizing enzymes. The microsomal aryl hydrocarbon hydroxylase activity increases significantly 24 hr after a single dose of 4 mg/kg and 48 hr after doses of 2 and 4 mg/kg, but no induction Ia found with 1 mg/kg. The binding from an equimolar dose is 35 times lower than the one found on mouse skin DNA and 300 times lower than that of N,Ndlmethylnitrosamine in rat liver. A good correlatlon exiats to the respective tumor formation in long-term studles.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{JaggiLutzSchlatter1978,
  author    = {Jaggi, W. and Lutz, Werner K. and Schlatter, C.},
  title     = {Covalent binding of ethinylestradiol and estrone to rat liver DNA in vivo},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61162},
  year      = {1978},
  abstract  = {Thecovalent bindingof [6,7-\(^3\)H]ethinylestradiol (EE)and [6,7-\(^3\)H]estrone (E) to liver DNA of 200 g female ratswas measured 8 h after the administration of 80 \(\mu\)g (9.2 mCi) estrogen by gavage. The binding is 1.5 for EE and 1.1 for E, expressedas binding to DNA/dose, in units of \(\mu\)mol hormonefmol DNA phosphate/mmole honnone/kg body wt. It is in the same order of magnitude as for benzene and about 10 000 tim es below the binding of typical liver carcinogens, such as aflatoxin B\(_1\) or N,N-dimethylnitrosamine.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{VivianiLutz1978,
  author    = {Viviani, A. and Lutz, Werner K.},
  title     = {Modulation of the binding of the carcinogen benzo(a)pyrene to rat liver DNA in vivo by selective induction of microsomal and nuclear aryl hydrocarbon hydroxylase activity},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61150},
  year      = {1978},
  abstract  = {The lnfluence of mlcrosomal and nuclear aryl hydrocarbon hydroxylase (AHH) actlvlty on the covalent blndlng of [G·3H]benzo(a )pyrene to rat llver DNA was evaluated in viWJ. lnductlon of mlcrosomal AHH was obtalned alter phenobarbltal treatment (160\% of control), whlch also lncreased DNA blndlng to 190\%, but left the nuclear actlvlty unchanged. Nuclear AHH was lnduced wlth dleldrln (150\%), and the blndlng was decreased to 75\%, whereaa the mlcrosomal AHH was at control Ievei. The lncreaslng effect of mlcrosomal AHH lnductlon as weil as the decreaslng effect of nuclear AHH lnductlon on the blndlng was shown clearly when the data of the Individual rata were uaed to solve the equatlon Binding = e•(mlcroeomal AHH) + b•(nuclear AHH) + c Multiple linear regresslon analysls wlth the data from 10 anlmala reaulted ln positive valuea for a and c, a negative value for b, and a good multiple correlatlon coefflclent of r = 0.974. Pretreatment wlth 3-methylcholanthrene ln· duced mlcrosomal AHH to 380\% of control and nuclear AHH to 590\% and lncreased the blndlng' to 175,.-o. The blndlng was hlgher than predlcted by the formula found, probably because the lncreaslng lnfluence of lnduced mlcrosomal AHH overahadowed the decreaslng effect of the nuclear AHH. The study ahows clearly that the blndlng of a forelgn compound to DNA in viWJ Ia dependent not only on mlcrosomal enzyme actlvltles but also on nuclear actlvltles even lf the latter are conslderably lower than thoae of mlcrosomes.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{LutzBraendleZbinden1978,
  author    = {Lutz, Werner K. and Br{\"a}ndle, E. and Zbinden, G.},
  title     = {Effect of gum Arabic on aminopyrine demethylation in rats},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61146},
  year      = {1978},
  abstract  = {Stimulation of aminopyrine demethylation induced in rats by oral or i.p. administration of phenobarbital was partially inhibited in animals receiving daily treatments of 2 x 200 mg/kg gum Arabic p.o.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{JaggiLutzSchlatter1979,
  author    = {Jaggi, W. and Lutz, Werner K. and Schlatter, C.},
  title     = {Comparative studies on the covalent binding of the carcinogen benzo(a)pyrene to DNA in various model systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61131},
  year      = {1979},
  abstract  = {The covalent binding of tritiated benzo(a)pyrene (BP) to DNA has been determined in rat liver in vivo, in rat liver perfused in situ, after incubation of BP with liver single cells, with liver homogenate, with liver microsomes and DNA, with fibroblasts from a rat granulorna pouch, and with · 2 cell lines. Li ver single cells were found to be a valuable compromise between the rnost sensitive system (microsomal incubation of BP with DNA) and the biologically most relevant system (in vivo ).},
  subject      = {Toxikologie},
  language  = {en}
}
@article{Lutz1979,
  author    = {Lutz, Werner K.},
  title     = {In vivo covalent binding of organic chemicals to DNA as a quantitative indicator in the process of chemical carcinogenesis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61122},
  year      = {1979},
  abstract  = {The covalent binding of chemical carcinogens to DNA of mammalian organs is expressed per unit dose, and a 'Covalent-Binding Index', CBI, is defined. CBI for various carcinogens span over 6 orders of magnitude. A similar range is observed for the carcinogenic potency in long-term bioassays on carcinogenicity. For the assessment of a risk from exposure to a carcinogen, the total DN A darnage can be estimated if the actual dose is also accounted for. A detailed description is given for planning and performing a DNA-binding assay. A complete literature survey on DNA binding in vivo (83 compounds) is given with a calculation of CBI, where possible, 153 compounds are listed where a covalent binding to any biological macromolecule has been shown in vivo or in vitro. Recent, so far unpublished findings with aflatoxin Mh macromolecule- bound aflatoxin Bh ·diethylstilbestrol, and 1,2-epithiobutyronitrile are included. A comparison of CBI for rat-liver DNA with hepatocarcinogenic potency reveals a surprisingly good quantitative correlation. Refinements for a DN A-binding assay are proposed. Possibilities and Iimitations in the use of D NA binding in chemical carcinogenesis are discussed extensively.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{VivianiDaenikenSchlatteretal.1980,
  author    = {Viviani, A. and D{\"a}niken, A. von and Schlatter, C. and Lutz, Werner K.},
  title     = {Effect of selected induction of microsomal and nuclear aryl hydrocarbon monooxygenase and epoxide hydrolase as well as cytoplasmic glutathione S-epoxide transferase on the covalent binding of the carcinogen benzo(a)pyrene to rat liver DNA in vivo},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61114},
  year      = {1980},
  abstract  = {Groups of four adult male rats [ZUR:SIV -Z] were pretreated with corn oil (control; 2 ml/kg/day i. p. for 3 days), trans-stilbene-oxide (SO; 200 mg/kg/day i. p. for 2 days), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 10 \(\mu\)g/kg i. p. once, 4 days before killing), phenobarbital (PB; 1 gjliter in the drinking water for 8 days), and dieldrin (20 mg/kg/day i. p. for 3 or 9 days). They received an injection of [G-\(^3\)H]benzo(a)pyrene (BaP, 31 \(\mu\)g/kg, 7.4. 10\(^9\) dpm/kg; i. v.) 16 h before killing. In the liver of each rat, five enzymatic activities and the covalent binding of BaP to DNA have been determined. The rnicrosomal aryl hydrocarbon monooxygenase activity (AHM) ranged frorn 75\% of control (SO) to 356\% (TCDD), the nuclear AHM from 63\% (SO) to 333\% (TCDD). Microsomal epoxide hydrolase activity (EH) was induced up to 238\% (PB), nuclear EH ranged from 86\% (TCDD) to 218\% (PB). A different extent of induction was observed in the two compartments. Highest induction of glutathione S-epoxide transferase activity (GST) was found with PB (202\%). The DNA binding of BaP was modulated within 79\% (dieldrin, 9 days) and 238\% of control (TCDD). An enzyme digest of control DNA was analysed by Sephadex LH-20 chromatography. Multiple linear regression analysis with all data expressedas o/o of control yielded the following equation: DNA Binding = 1.49 · Microsomal AHM- 1.07 · Nuclear AHM+ 0.33 · Microsomal EH- 0.52 · N uclear EH+ 0.11 · Cytoplasmic GST + 58.2. From this analysis it is concluded that (1) AHM located in the endoplasmic reticulum is most important in the formation of DNA-binding metabolites, (2) EH in the same compar.tment is not determinative in thls respect nor has it a protective effect, (3) both membrane-bound enzyme activities located in the nucleus may inactivate potential ultimate carcinogens, and ( 4) cytoplasmic GST probably cannot reduce DNA binding due to its subcellular localization.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{JaggiLutzLuethyetal.1980,
  author    = {Jaggi, W. and Lutz, Werner K. and L{\"u}thy, J. and Zweifel, U. and Schlatter, C.},
  title     = {In vivo covalent binding of aflatoxin metabolites isolated from animal tissue to rat-liver DNA},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61101},
  year      = {1980},
  abstract  = {Ring-labelled [\(^{14}\)C)aflatoxin B\(_1\) (AFB\(_1\)), prepared by biosynthesis. or generally labelled [\(^3\)H]AFB\(_1\) was administered by oral gavage to young adult male rats. After 6 hr. the liver was removed and two fractions were isolated, namely macromolecules, which contamed about 3 \% of the initial dose of AFB\(_1\) radioactivity. and water-soluble, low-molecular aftatoxin conjugates containing about0·2\% of the administered radioactivity. These two fractions were administered orally to other rats in order to determine the potential of radioactive aftatoxin residues for covalent binding to DNA. Such binding can be used as an indicator for carcinogenic potency. Liver DNA was isolated 9-12 hr after admmistration of the aflatoxin derivatives and in no case was any radioactivity detected on the DNA. It can be deduced on the basis of the limit of detection of radioactivity on the DNA, that macromolecule bound AFB\(_1\) derivatives are at least 4000 times less active than AFB\(_1\) with respect to covalent binding to rat-liver DNA. and that the water-soluble conjugates are at least 100 times less potent than AFB, itself. It is concluded that the carcinogenic risk for humans who consume liver or meat. containing such aflatoxin residues is negligible when compared with the risk from intake of aftatoxins in other food items.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{LutzJaggiLuethyetal.1980,
  author    = {Lutz, Werner K. and Jaggi, W. and L{\"u}thy, J. and Sagelsdorff, P. and Schlatter, C.},
  title     = {In vivo covalent binding of aflatoxin B\(_1\) and aflatoxin M\(_1\) to liver DNA of rat, mouse and pig},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61097},
  year      = {1980},
  abstract  = {[\(^{14}\)C] Aflatoxin B\(_1\) (AFB\(_1\)) was isolated from cultures of Aspergillus parasiticus grown on [1-\(^{114}\)C] sodium acetate. Covalent binding of AFB1 to liver DNA of rat and mouse was determined 6-8 h afteroral administration. The effectiveness of covalent binding, expressedas DNA binding per dose in the units of a 'Covalent Binding Index' (CBI), (\(\mu\)mol aflatoxin/mol DNA nucleotides)/(mmol aflatoxin/kg animal), was found to be 10 400 for rats and 240 for mice. These CBI partly explain the different susceptibility of the two species for the incidence of hepatic tumors. The corresponding values for pig liver DN A, 24 and 48 h after oral administration, were found to be as high as 19 100 and 13 300. DNA-binding has not so far been reported for this species although it could represent an appropriate animal model for studies where a human-like gastrointestinal tract physiology is desirable. Aflatoxin M \(_1\) ( AFM\(_1\)) is a metabolite found in the milk of cows that have been fed AFB\(_1\)-contaminated diet. [\(^{14}\)C] AFM\(_1\) was also found to be produced by cultures of A. parasiticus giving a yield of about 0.3\% of the total aflatoxins. A test for covalent binding to rat liver DN A revealed a CBI of 2100 shoWing that AFM\(_1\) must also be regarded as a strong hepatocarcinogen. It is concluded that AFB\(_1\) contaminations should be avoided in dairy feed.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{DaenikenLutzSchlatter1981,
  author    = {D{\"a}niken, A. von and Lutz, Werner K. and Schlatter, C.},
  title     = {Lack of covalent binding to rat liver DNA of the hypolipidemic drugs clofibrate and fenofibrate},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61087},
  year      = {1981},
  abstract  = {\(^{14}\)C-Labelled clofibric acid and fenofibric acid were administered p.o. to 200 g male and female rats. After 10 h, liver nuclear DNA and protein were isolated and the radioactivity was determined. Binding to protein was clearly measurable whereas no binding to DNA could be detected from any drug. A comparison of the Iimit of detection of such DNA binding with well-known chemical carcinogens revealed that the known hepatocarcinogenicity of clofibrate cannot be based upon an initiating, DNA damaging, mode of action but must be due to other, nongenotoxic, mechanisms such as peroxisome proliferation, hepatomegaly, or cytotoxicity due to protein binding. The risk assessment in man and the interpretation of the carcinogenicity data for rodents are discussed.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{DaenikenFriederichLutzetal.1981,
  author    = {D{\"a}niken, A. von and Friederich, U. and Lutz, Werner K. and Schlatter, C.},
  title     = {Tests for mutagenicity in Salmonella and covalent binding to DNA and protein in the rat of the riot control agent o-chlorobenzylidene malononitrile (CS)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61073},
  year      = {1981},
  abstract  = {The aim of this study was to determine whether o-chlorobenzylidene malononitrile ( CS) exhibits any genotoxic activity towards Salmonella or mammalian DNA in vivo. CS was synthesized with a [\(^{14}\)C]-label at the benzylic carbon atom. It was administered i. p. at a dose level of 13 mg/kg (1 mCi/kg) to young adult male rats. Liverand kidney DNA was isolated after 8, 25, and 75 h. The radioactivity was at (liver, 8 and 75 h) or below (all other samples) the limit of detection of 3 dpm. Therefore, a possible binding of CS to DNA is at least 10\(^5\) times lower than that of the strong hepatocarcinogen aflatoxin B1, and 4,000 times lower than that of vinyl chloride. In contrast to this lack of DNA binding, but in agreement with the chemical reactivity of CS, a binding to nuclear proteins could be detected with specific activities ranging between 50 and 121 dpm/mg for liver and between 3 and 41 dpm/mg for kidney. Protein binding could well be responsible for its pronounced cytotoxic effects. Cs was also tested in the Ames Salmonella/microsome assay. Strains TA 1535, TA 1537, TA 1538, TA 98, and TA 100 were used with or without pre-incubation. Only with strain TA 100 and only without pre-incubation, a doubling of the number of revertants was detectable at the highest dose Ievels used, 1,000 and 2,000 !lg CS per plate. With pre-incubation of TA 100 with CS, a slight increase of the number of revertants was seen at 100 and 500 !lg per plate, and a subsequent fall below control values at 1,000 J.tg. A check for the number of surviving bacteria revealed a strong bacteriotoxicity of the higher doses of es so that the calculated mutation frequencies, i.e., the oumber of revertants per number of surviving bacteria, increased with doses up to 500 !J.g. This toxicity could be counteracted in part by the addition of increasing amounts of rat liver microsomes. In the view of these results, and taking into account the rare and low exposure of man, it is concluded that CS will not create a risk for the induction of point mutations or of carcinogenic processes mediated by DNA binding.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{LutzJaggiSchlatter1982,
  author    = {Lutz, Werner K. and Jaggi, W. and Schlatter, C.},
  title     = {Covalent binding of diethylstilbestrol to DNA in rat and hamster liver and kidney [Short Communication]},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61066},
  year      = {1982},
  abstract  = {No abstract available},
  subject      = {Toxikologie},
  language  = {en}
}
@article{MeierBratschiLutzSchlatter1983,
  author    = {Meier-Bratschi, A. and Lutz, Werner K. and Schlatter, C.},
  title     = {Methylation of liver DNA of rat and mouse by N-nitrosodimethylamine formed in vivo from dimethylamine and nitrite},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61052},
  year      = {1983},
  abstract  = {The extent of formation of N-nitrosodimethylaminc {NDMA) in the stomachs of rats and mice after sirnultancous oral administration of [\(^{14}\)C]dimethylamine and potassium nitrite was determined by measuring the methylation of liver DNA. With doses of around 1 mg dimethylamine hydrochloride/ kg body weight and 50 mg potassium nitrite/kg body weight. 0,8 \% of the amine was nitrosated on average. The individual fluctuations ranged from 0.2 to 1.30\% in the rat and from 0.2 to 1.9\% in the mouse. Simultaneous administration of 50 mg sodium ascorbate (vitamin Cl/kg body weight inhibited the nitrosation by ahout 80\% while 50 mg \(\alpha\)-tocopherol acetate [Vitamin E)/kg body weight reduced the nitrosation by about a half. Assuming similar kinctics and conditions of nitrosation in rats and man. a comparison of the formation of NDMA in vivo from dietary dimethylamine and nitrite with the estimated human uptake of preformed N DMA revealed that in vitro formation in the stomach of man is probably negligible.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{JauchLutz1983,
  author    = {Jauch, A. and Lutz, Werner K.},
  title     = {In vivo assay for somatic point mutations induced by genotoxic carcinogens: incorporation of [\(^{35}\)S]methionine into a rat liver cytochrome b\(_5\) normally lacking sulphur-containing amino acids},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61047},
  year      = {1983},
  abstract  = {The trypsin fragments of rat liver microsomal cytochron1e b\(_5\) (Tb\(_5\)) lack both methionine (met) and cysteine (cys), i.e., the sulphur-containing antino acids. Tb\(_5\) should therefore contain no 358-radioactivity after isolation from animals treated wHh [\(^{35}\)S]met or [\(^{36}\)S]cys. If, however, the nucleic acids coding for this polypeptide have been damaged by a genotoxic carcinogen, a miscoding could result in an incorporation of met or cys into the polypeptide so that Tb\(_8\) could now be \(^{36}\)S-radiolabelled. Two experiments are descrihed. the first one where a toxic regimen of N -nitrosomorpholine (NNM) to rats resulted in a significant increase of \(^{35}\)S-radioactivity in the Tbs of liver microsomes, and a second experiment with a non-toxic regimen of N,N diethylnitrosamine (DENA), where no increase was observable.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{SagelsdorffLutzSchlatter1983,
  author    = {Sagelsdorff, P. and Lutz, Werner K. and Schlatter, C.},
  title     = {The relevance of covalent binding to mouse liver DNA to the carcinogenic action of hexachlorocyclohexane isomers},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61039},
  year      = {1983},
  abstract  = {[\(^3\)H]Hexachlorocyclohexane (HCH) was synthesized by chlorination of [\(^3\)H]benzene prepared by catalytic tritiation of benzene with tritiated water. The isomers of HCH were separated by adsorption chromatography on silica gel. In order to determine the covalent binding to DNA, [\(^3\)H]HCH was administered to male mice by oral gavage, and liver DNA was isolated via cbromatin. The specific radioactivity of the DNA was nonnalized by the dose administered and expressed in the molar units of the Covalent binding index, CBI = DNA damage/dose = (\(\mu\)mol bound HCH/mol DNA nucleotide)/(mmol HCH administered/kg body weight). CBI values of - 0.2 were found 10 h after the administration of alpha- and gamma-HCH. Enzymatic digestion of the DNA to the nucleosides and h.p.l.c. analysis revealed that - 40\% of the radioactivity co-migrated with the natural nucleosides. At elution volumes known to contain the more lipophilic carcinogen-nucleoside adducts, - 10\% of the radioactivity could be detected. The remaining 50\% of th,e radioactivity eluted with the front, representing a mixture of oligonucleotide- HCH adducts and/or hydrophilic degradation products which were strongly bot not covalently associated with intact DNA. Therefore, a true CBI of 0.02-0.1 must be expected both for alpha- and gamma-HCH. This CBI is by a factor of 10\(^5\) -10\(^6\) below the value found with the strongest DNAbinding carcinogens like aflatoxin B1 or dimethylnitrosamine and is unlikely to be decisive for the liver tumor induction in mice because of the foUowing additional findings: (i) both isomers gave rise to similar Ievels of DNA darnage although the alpha-isomer is a much morepotent tumor inducer. This similarity was seen not only at the time of m{\"a}ximum binding but up to 10 days after oral administration; (ii) three mouse strains with apparently different susceptibility to tumor induction by gamma-HCH could not be distinguished with respect to DNA binding; (iii) the level of DNA binding of alpha-HCH (CBI = 0.02-0.1) is more than three orders of magnitude lower than would be expected if the mechanism of tumor induction was by genotoxicity mediated by DNAbinding. For a preliminary investigation on a potential stimulatory effect on liver DN A replication and ceU division, [\(^{14}\)]thymidine was admlnistered i.p. 3.5 h before sacrifice of the [\(^3\)H]HCH-treated mice. The alpha-isomer was found to be more potent than the gamma-isomer in this respect. Taken together, our data allow the conclusion that the non- mutational processes must be more important for the carcinogenicity of HCH.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{LutzBuesserSagelsdorff1984,
  author    = {Lutz, Werner K. and B{\"u}sser, M. T. and Sagelsdorff, P.},
  title     = {Potency of carcinogens derived from covalent DNA binding and stimulation of DNA synthesis in rat liver},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61026},
  year      = {1984},
  abstract  = {~n order to investigate the role of the stimu~ation of ceU division for the initiation (and possi:bly promotion) of live·r tumors by chemical carcinogens, the incorporation of radiolabeUed thymidine into liver DNA was dete:rmined in male rats. Single doses of various level!s of af.latoxin 81, benzidine and carbon tetrachloride (aU known to be genotoxic via DNA binding} did not affect cell division, whereas several hepatoca:rcinogens known not to bind to DNA (alphaHCH, dofibrate, and 2,3;7,8-t!etrachlorodiibenzo~p~dioxin) gave rise to a dosedependent stimulation of Ii ver DNA synthesis within 24 h. An equation combining the infl.uences of mitotic stimu:lation, expressed as dose required to double the contro~ Ievei of DNA synthesis, and DNA binding potency, exp:ressed as t.he Covalent Binding Index, correliated weil with the cardnogenk potency for both dasses of hepatocardnogens.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{HuberLutz1984,
  author    = {Huber, K. W. and Lutz, Werner K.},
  title     = {Methylation of DNA by incubation with methylamine and nitrite},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61011},
  year      = {1984},
  abstract  = {DNA was incubated in septum-closed reaction vials with [\(^{14}\)C]methylamine and nitrite. The DNA was purified, hydrolysed with hydrochloric acid, and the purines were analysed by h.p.l.c. 7-Methylguanine was detectable as a result of DN A methylation in experiments perfonned in 100 mM acetate at pH 4. Using different concentrations of amine and nitrite a first order reaction for total amine and a second order for total nilrite could be shown. A study on the pH dependence using 100 mM malonate buffer, pH 2.0-6.0, revealed a maximum rate at pH 3.5, with steep slopes above and below this pH value, in agreement with a mathematical analysis of the reaction equations. The data show that the alkylating agent fonned spontaneously by nitrosation and deamination of a primary amine has a long enough lifetime to react with DNA in vitro. Using the reactioil orders established here, an extrapolation to lower concentrations found in the stomach can now be perfonned. Future in vivo experiments on the methylation of gastro-intestinal DNA then would show to what extent DNA in a cell is protected from alkylation.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{DaenikenLutzJaeckhetal.1984,
  author    = {D{\"a}niken, A. von and Lutz, Werner K. and J{\"a}ckh, R. and Schlatter, C.},
  title     = {Investigation of the potential for binding of Di(2-ethylhexyl) phthalate (DEHP) and Di(2-ethylhexyl) adipate (DEHA) to liver DNA in vivo},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-61004},
  year      = {1984},
  abstract  = {Investigation of the Potential for Binding of Di(2-ethylhexyl) Phthalate (DEHP) and Di(2- ethylhexyl) Adipate (DEHA) to Liver DNA in Vivo. VON D{\"A}NIKEN, A., LUTZ, W. K., J{\"A}CKH, R., AND ScHLATTER, C. (1984). Toxico/. App/. Pharmaco/. 73, 373-387. It was the aim oftbis investigation to determine whether covalent binding of di(2-ethylhexyl) phthalate (DEHP) to rat liver DNA and of di(2-ethylhexyl) adipate (DEHA) to mouse liver DNA could be a mechanism of action contributing to the observed induction of liver tumors after lifetime feeding of the respective rodent species with high doses of DEHP and DEHA. For this purpose, DEHP and DEHA radiolabeled in different parts of the molecule were administered orally to female rats and mice, respectively, with or witbout pretreatment for 4 weeks with 1\% unlabeled compound in the diet. Liver DNA was isolated after 16 hr and analyzed for radioactivity. The data were converted to a covalent binding index, CBI = (micromoles of substance bound per mole of DNA nucleotides)/(millimoles of substance applied per kilogram body weight), in order to allow a quantitative comparison also with other carcinogens and noncarcinogens. Administration of [\(^{14}\)H]carboxylate-labeled DEHP to rats resulted in no measurable DNA radioactivity. The Iimit of detection, CBI < 0.02 was about 100 times below the CBI of compounds where an observable tumor-inducing potential could be due to genotoxicity. With [\(^{14}\)C]- and [\(^{3}\)H]DEHP labeled in the alcohol moiety, radioactivity was clearly measurable in rat liver DNA. HPLC analysis of enzyme-degraded or acid-hydrolyzed DNA revealed that the natural nucleosides or purine bases were radiolabeled whereas no radioactivity was detectable in those fractions where tbe carcinogenmodified nucleoside or base adducts are expected. The respective Iimits of detection were at 0.07 and 0.04 CBI units for the \(^{14}\)C and \(^{3}\)H Iabels, respectively. The experiments with [\(^{14}\)C]- and [\(^{3}\)H]DEHA, labeled in the alcobol moiety and administered to mice, revealed aminute radioactivity of <50 dpm/mg liver DNA, too little to allow a nucleoside analysis to determine that fraction of the radioactivity which bad been incorporated via biosynthesis. Expressed in the CBI units, values of 0.05 to 0.15 for \(^{14}\)C and 0.01 to 0.12 for \(^{3}\)H resulted. Determination of the level· of \(^{14}\)C02 expiration revealed a linear correlation with the speciftc activity of DNA. Experiments with 2-ethyl[ 1-\(^{14}\)C]hexanol perfonned with both rats and mice allowed the conclusion tbat most if not all DEHA radioactivity in mouse liver DNA was due to biosynthetic incorporation. A maximum possible true DNA binding by DEHA must be below CBI 0.01. Pretreatment of the animals witb unlabeled compound bad no effect on the DNA radioactivities in either species. The present negative data, in conjunction witb other negative short-term tests for mutagenicity, strongly indicate that covalent interaction with DNA is highly unlikely to be the mode of tumorigenic action of DEHP and DEHA in rodents.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{CaviezelLutzMininietal.1984,
  author    = {Caviezel, M. and Lutz, Werner K. and Minini, U. and Schlatter, C.},
  title     = {Interaction of estrone and estradiol with DNA and protein of liver and kidney in rat and hamster in vivo and in vitro},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60995},
  year      = {1984},
  abstract  = {(6,7-\(^3\)H] Estrone (E) and [6,7-\(^3\)H]estradiol-17ß (E\(_2\)) have been synthesized by reduction of 6-dehydroestrone and 6-dehydroestradiol with tritium gas. Tritiated E and E\(_2\) were administered by oral gavage to female rats and to male and female hamsters on a dose level of about 300 \(\mu\)g/kg (54 mCi/kg). After 8 h, the liver was excised from the rats; liver and kidneys were taken from the hamsters. DNA was purified either directly from an organ homogenate or via chromatin. The radioactivity in the DNA was expressed in the units of the Covalent Binding Index, CBI = (\(\mu\)mol chemical bound per mol Similar considerations can be made for the liver where any true covalent DNA binding must be below a Ievel of 0.01. It is concluded that an observable tumor induction by estrone or estradiol is unlikely to be due to DNA binding. DNA-P)/(mmol chemical administered per kg b.w.). Rat liver DNA isolated via chromatin exhibited the very low values of 0.08 and 0.09 for E and E\(_2\) respectively. The respective figures in hamster liver were 0.08 and 0.11 in females and 0.21 and 0.18 in the males. DNA isolated from the kidney revealed a detectable radioactivity only in the female, with values of 0.03 and 0.05 for E and E\(_2\) respectively. The values for male hamster kidney were < 0.01 for both hormones. The minute radioactivity detectable in the DNA samples does not represent covalent binding to DNA, however, as indicated by' two sets of control experiments. (A) Analysis by HPLC of the nucleosides prepared by enzyme digest of liver DNA isolated directly or via chromatin did not reveal any consistent peak which could have been attributed to a nucleoside-steroid adduct. (B) All DNA radioactivity could be due to protein contaminations, because the specific activity of chromatin protein was determined to be more than 3 ,000 tim es high er than of DNA. The high affinity of the hormone to protein was also demonstrated by in vitro incubations, where it could be shown that the specific activity of DNA and protein was essentially proportional to the concentration of radiolabelled hormone in the organ homogenate, regardless of whether the animal was treated or whether the hormone was added in vitro to the homogenate. Carcinogens acting by covalent DNA binding can be classified according to potency on the basis of the Covalent Binding Index. Values of 10\(^3\)-10\(^4\) have been found for potent, 10\(^2\) for moderate, and 1-10 for weak carcinogens. Since estrone is moderately carcinogenic for the kidney of the male hamster, a CBI of about 100 would be expected. The actually measured Iimit of detection of 0.01 places covalent DNA binding among the highly unlikely mechanisms of action.},
  subject      = {Toxikologie},
  language  = {en}
}