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Characterization of a small intestine microsomal preparation for use in the Salmonella mutagenicity assay
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II.1B.2 Walters, J.M., and R.D. Combes, Department of Biological Sciences, Portsmouth Polytechnic, Portsmouth (Great Britain) Characterization of a small intestine microsomal preparation for use in the Salmonella mutagenicity assay
A methodology has been developed for use in the Ames plate-incorporation assay of a microsomal metabolizing system from villous tip cells of rat small intestine. The technique, comprising vibration of everted gut segments followed by gentle lysis and homogenization, has been studied for its ability to yield preparations capable of activating several promutagens. The effects of pretreatment of animals with different inducers of the cytochrome-mixed function oxidase system have been investigated. All the chemicals caused reproducible dose-related mutagenicity. Minimal effective concentrations required for revertant doubling were in the order: aflatoxin B1 > benzo[a]pyrene > aminoanthracene, aminofluorene > acetylaminofluorene > cyclophosphamide. Activating capacity was proportional to level of microsomal protein plated. Maximum revertant counts were lower than when using liver microsomes. Qualitative differences between hepatic and gut activation were seen. Lower concentrations of cyt P450, NADP-cyt c reductase and several other phase-I activation enzymes were recovered in gut extracts. The intestine was less susceptible to the enhancing effects of enzyme inducers. Hepatic and intestinal activating efficiencies (expressed as revertants/nmole cyt P450) were comparable. The small intestine may thus be an important initial site for activation of putative dietary mutagenic and carcinogenic constituents during uptake.
II.1B.3 D e Raat, W.K. l, F.L. Schulting 2 and E. Burghardt 2, 1 Division of Technology for Society TNO, P.O. Box 217, 2600 AE Delft, and 2 TNO Research Institute for Environmental Hygiene, P.O. Box 214, 2600 AE Delft (The Netherlands) Mutagenicity of air components which are too volatile to be sampled by high-volume sampling with glass-fibre filters
The applicability of polyurethane foam (PUF) for sampling volatile mutagens in air was investigated. Sampling was carried out with a glass-fibre filter followed by a PUF plug. The filters and the PUF plugs were Soxhlet-extracted with methanol and the extracts were tested with the Ames test (TA98 with and without $9 fraction). Blank PUF extracts appeared to be mutagenic with $9, making intensive pre-extraction necessary. After sampling, the PUF extracts showed clear mutagenicity. The PUF effect behaved independently of the filter effect; it was more S9-dependent and could have the same magnitude. This indicates that pollutants, too volatile to be sampled by filtration with glass-fibre filters, contain mutagens. Chemical analyses of the extracts showed that a large part of the polycyclic aromatic hydrocarbons (4 rings or less) pass the glass-fibre filters but are adsorbed by the PUF.
II.1B.2 Walters, J.M., and R.D. Combes, Department of Biological Sciences, Portsmouth Polytechnic, Portsmouth (Great Britain) Characterization of a small intestine microsomal preparation for use in the Salmonella mutagenicity assay
A methodology has been developed for use in the Ames plate-incorporation assay of a microsomal metabolizing system from villous tip cells of rat small intestine. The technique, comprising vibration of everted gut segments followed by gentle lysis and homogenization, has been studied for its ability to yield preparations capable of activating several promutagens. The effects of pretreatment of animals with different inducers of the cytochrome-mixed function oxidase system have been investigated. All the chemicals caused reproducible dose-related mutagenicity. Minimal effective concentrations required for revertant doubling were in the order: aflatoxin B1 > benzo[a]pyrene > aminoanthracene, aminofluorene > acetylaminofluorene > cyclophosphamide. Activating capacity was proportional to level of microsomal protein plated. Maximum revertant counts were lower than when using liver microsomes. Qualitative differences between hepatic and gut activation were seen. Lower concentrations of cyt P450, NADP-cyt c reductase and several other phase-I activation enzymes were recovered in gut extracts. The intestine was less susceptible to the enhancing effects of enzyme inducers. Hepatic and intestinal activating efficiencies (expressed as revertants/nmole cyt P450) were comparable. The small intestine may thus be an important initial site for activation of putative dietary mutagenic and carcinogenic constituents during uptake.
II.1B.3 D e Raat, W.K. l, F.L. Schulting 2 and E. Burghardt 2, 1 Division of Technology for Society TNO, P.O. Box 217, 2600 AE Delft, and 2 TNO Research Institute for Environmental Hygiene, P.O. Box 214, 2600 AE Delft (The Netherlands) Mutagenicity of air components which are too volatile to be sampled by high-volume sampling with glass-fibre filters
The applicability of polyurethane foam (PUF) for sampling volatile mutagens in air was investigated. Sampling was carried out with a glass-fibre filter followed by a PUF plug. The filters and the PUF plugs were Soxhlet-extracted with methanol and the extracts were tested with the Ames test (TA98 with and without $9 fraction). Blank PUF extracts appeared to be mutagenic with $9, making intensive pre-extraction necessary. After sampling, the PUF extracts showed clear mutagenicity. The PUF effect behaved independently of the filter effect; it was more S9-dependent and could have the same magnitude. This indicates that pollutants, too volatile to be sampled by filtration with glass-fibre filters, contain mutagens. Chemical analyses of the extracts showed that a large part of the polycyclic aromatic hydrocarbons (4 rings or less) pass the glass-fibre filters but are adsorbed by the PUF.