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- Clemedson, Cecilia, et al.
(författare)
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Development of an in vitro test battery for the estimation of acute human systemic toxicity : An outline of the EDIT project. Evaluation-guided Development of New In Vitro Test Batteries
- 2002
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Ingår i: ATLA (Alternatives to Laboratory Animals). - 0261-1929. ; 30:3, s. 313-321
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the Evaluation-guided Development of new In Vitro Test Batteries (EDIT) multicentre programme is to establish and validate in vitro tests relevant to toxicokinetics and for organ-specific toxicity, to be incorporated into optimal test batteries for the estimation of human acute systemic toxicity. The scientific basis of EDIT is the good prediction of human acute toxicity obtained with three human cell line tests (R(2) = 0.77), in the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme. However, the results from the MEIC study indicated that at least two other types of in vitro test ought to be added to the existing test battery to improve the prediction of human acute systemic toxicity - to determine key kinetic events (such as biotransformation and passage through biological barriers), and to predict crucial organ-specific mechanisms not covered by the tests in the MEIC battery. The EDIT programme will be a case-by-case project, but the establishment and validation of new tests will be carried through by a common, step-wise procedure. The Scientific Committee of the EDIT programme defines the need for a specific set of toxicity or toxicokinetic data. Laboratories are then invited to perform the defined tests in order to provide the "missing" data for the EDIT reference chemicals. The results obtained will be evaluated against the MEMO (the MEIC Monograph programme) database, i.e. against human acute systemic lethal and toxicity data. The aim of the round-table discussions at the 19th Scandinavian Society for Cell Toxicology (SSCT) workshop, held in Ringsted, Denmark on 6-9 September 2001, was to identify which tests are the most important for inclusion in the MEIC battery, i.e. which types of tests the EDIT programme should focus on. It was proposed that it is important to include in vitro methods for various kinetic events, such as biotransformation, absorption in the gut, passage across the blood-brain barrier, distribution volumes, protein binding, and renal clearance/accumulation. Models for target organ toxicity were also discussed. Because several of the outlier chemicals (paracetamol, digoxin, malathion, nicotine, paraquat, atropine and potassium cyanide) in the MEIC in vivo-in vitro evaluation have a neurotoxic potential, it was proposed that the development within the EDIT target organ programme should initially be focused on the nervous system.
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| 2. |
- Romert, Lennart, 1949-
(författare)
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Mutagenesis induced by xenobiotics : factors of importance and modification, with special emphasis on glutathione and glutathione transferases
- 1991
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Genetic changes induced by chemical agents can result in cancer. Such tumor formation can be linked to activationof oncogenes, often through specific, definable mutagenic events, e.g., single base-pair mutation in specific codons.Most mutagenic and carcinogenic compounds must be activated in order to obtain mutagenic and carcinogenicproperties. This activation can be spontaneous through chemical reactions with other compounds, but is mostfrequently mediated through the action of enzymes. Bioactivated compounds can subsequently be detoxicated throughenzymatic conjugation with hydrophilic biomolecules or, occasionally in spontaneous reactions.This thesis deals with certain factors influencing the chain of event resulting in mutagenicity detected in vitro or invivo. Mutagenicity was detected as HPRT mutants in V79 Chinese hamster cells or by the use of the Somatic Mutationand Recombination Test in Drosophila melanogasler. V79 cells, which lack the capacity to bioactivate the modelcompounds studied, were also used as target cells for the detection of mutagenicity in co-cultivation with other cellscompetent in such bioactivation. By the use of this technique, it was possible to investigate factors of importance forbioactivation and detoxication in both primary non-dividing cells, as well as in various established cell lines.During this study several model compounds have been used. Compounds that either require metabolic activation toobtain mutagenic properties or that are spontaneously activated. Compounds belonging to the former group werebenzo(a)pyrene (B(a)P), its 7,8-diol and 1,2-dichloroethane (DCE). The latter group was represented byA'-methyl-A'1.nitro-W-nitrososoguanidine (MNNG), V-ethyl-W -nitro-W-nitrososoguanidine (ENNG) and nitrosocimetidine (NC).The results obtained are presented in six separate publications. In paper I co-cultivation experiments with alveolarmacrophages (PAMs) show that B(a)P-induced mutagenicity was enhanced 5-10 fold as a consequence of thephagocytic process triggered by the addition of particles. In the study presented in paper II the principal aim was tocompare human PAMs from smokers and non-smokers with respect to their capacity to induce mutations in cocultivatedV79 cells when treated with B(a)P-7,8-diol. No statistical difference between the two groups was detected.Papers IV and V deals with the importance of glutathione transferases (GSTs) for the mutagenicity. The resultspresented in paper IV show the protective role of certain GSTs in mutagenesis induced by polycyclic aromatichydrocarbons. However, the results presented in paper V indicate that GSTs can alto participate in bioactivation ofcertain compounds, e.g., DCE.In papers III and VI the influence of glutathione and other thiols on the mutagenicity of MNNG, ENNG and NC isinvestigated. These compounds are spontaneously activated by nucleophiles such as thiols. If this activation occursextracellularly, the products also react extracellularly with molecules in the surroundings. Therefore, due to their highreactivity these products are unable to reach the DNA and cause mutations. On the other hand, if this activation occursintracellularly, these compounds are highly mutagenic and the mutagenicity is also dependent on the intracellular levelof thiols.
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