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Screening of genotoxic fungal metabolites by SOS chromotest
104 Fisher 344 rats were intrarectally given test chemicals, and the colon mucosa was cut into small pieces and cultured in L-15 medium containing 370 kBq [3H]dThd/ml in the presence or absence of 10 mM hydroxyurea (HU) for detection of UDS or TDS, respectively. UDS and TDS were markedly increased by a well-known colon carcinogen 1,2-dimethylhy: drazine (DMH), at doses of up to 75 mg/kg body weight and its maximum activity was observed 6 h after administration. After treatment with azoxymethane (AOM), a metabolite of DMH, TDS was decreased gradually and UDS was increased. These results suggest stimulation of DNA replicative synthesis and also probable induction of DNA repair by DMH and the metabolite. The colon tumor promoters deoxycholate (DOC), lithocholic acid (LCA) and sodium cholate (SC) increased TDS dose- and time-dependently. The TDS-stimulating activity of secondary bile acids (DOC, LCA) is more marked than that of primary bile acid (SC). We also found that DOC enhanced UDS and TDS induced by DMH pretreatment. It is suggested that bile acids exhibit their tumorpromoting activity by stimulation of cell proliferation in the colon mucosa. These TDS-enhancing effects were suppressed by CaC12 pretreatment.
53 Sakai, M., K. Abe, Y. Sugiura and Y. Ueno, Department of Toxicology and Microbial Chemistry, Faculty of Pharmaceutical Sciences, Science University of Tokyo, Ichigaya, Shinjuku-ku, Tokyo 162 (Japan)
Screening of genotoxic fungal metabolites by SOS chromotest With the aim of surveying genotoxic fungal metabolites, the SOS chromotest with E. coli PQ37 was performed by the modified method of Quillardet et al. (1982). Seventy strains of Aspergillus, including their teleomorph, and 130 strains of Penicillium were tested. 2 g of rice grain were inoculated with fungi, and after culture for 3 weeks at 25 ° C, the moldy rice grains were extracted with 6 ml of methanol. The methanol extracts dissolved in DMSO were tested by the SOS chromotest in a microtiter plate in the presence or absence of $9 mix. fl-Galac-
tosidase activity was measured at 405 nm, and those samples that induced more than a doubling compared to the solvent control were defined as positive. No positive strains were found in Penicillium. In Aspergillus, 4 and 10 strains were positive, in the presence and absence of $9, respectively. Positive strains were 4 groups of A. flavus, A. nidulans, A. ustus and A. glaucus. Nine out of 10 strains of Emericella such as E. dentata, E. Quadrilineata and E. rugulosa produced mutagenic substances. TLC analysis suggested that one of these compounds was sterigmatocystin.
54 Sasagawa, C., and T. Matsushima, Department of Molecular Oncology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108 (Japan)
Mutagenicities of indole derivatives after nitrite treatment Tyrosine, tryptophan, histidine and their decarboxylated derivatives, tyramine, tryptamine and histidine (each 50 mM) were treated with 500 mM nitrite at pH 3 for 1 h. Tyramine and tryptaminc showed strong mutagenicity without and with $9 mix on S. typhimurium TA98 and TA100, and E. coli WP2 uvrA/pKMlOl. Tyrosine and tryptophan showed moderate mutagenicity while histidine and histamine did not show any mutagenicity. Fourteen indole derivatives of tryptophan metabolites in animals or plants (each 10 mM) were treated with 100 mM nitrite at pH 3. All indole derivatives except isatin showed mutagenicity without metabolic activation, lndole acetate, indole pyruvate, indole-3-acetonitrile, indole, 5hydroxytryptamine and tryptamine showed strong mutagenicity (> 103 revertants//~mole). Indole aldehyde, 5-methoxyindole acetate, indole acetaldehyde, indole acetamide and tryptophan showed moderate mutagenicity (up to 102 revertants/#mole). 5-Hydroxyindole acetate and indole lactate showed weak mutagenicity. Mutagens were possibly formed endogenously by the reaction of tryptophan metabolites and nitrite in the body.
53 Sakai, M., K. Abe, Y. Sugiura and Y. Ueno, Department of Toxicology and Microbial Chemistry, Faculty of Pharmaceutical Sciences, Science University of Tokyo, Ichigaya, Shinjuku-ku, Tokyo 162 (Japan)
Screening of genotoxic fungal metabolites by SOS chromotest With the aim of surveying genotoxic fungal metabolites, the SOS chromotest with E. coli PQ37 was performed by the modified method of Quillardet et al. (1982). Seventy strains of Aspergillus, including their teleomorph, and 130 strains of Penicillium were tested. 2 g of rice grain were inoculated with fungi, and after culture for 3 weeks at 25 ° C, the moldy rice grains were extracted with 6 ml of methanol. The methanol extracts dissolved in DMSO were tested by the SOS chromotest in a microtiter plate in the presence or absence of $9 mix. fl-Galac-
tosidase activity was measured at 405 nm, and those samples that induced more than a doubling compared to the solvent control were defined as positive. No positive strains were found in Penicillium. In Aspergillus, 4 and 10 strains were positive, in the presence and absence of $9, respectively. Positive strains were 4 groups of A. flavus, A. nidulans, A. ustus and A. glaucus. Nine out of 10 strains of Emericella such as E. dentata, E. Quadrilineata and E. rugulosa produced mutagenic substances. TLC analysis suggested that one of these compounds was sterigmatocystin.
54 Sasagawa, C., and T. Matsushima, Department of Molecular Oncology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108 (Japan)
Mutagenicities of indole derivatives after nitrite treatment Tyrosine, tryptophan, histidine and their decarboxylated derivatives, tyramine, tryptamine and histidine (each 50 mM) were treated with 500 mM nitrite at pH 3 for 1 h. Tyramine and tryptaminc showed strong mutagenicity without and with $9 mix on S. typhimurium TA98 and TA100, and E. coli WP2 uvrA/pKMlOl. Tyrosine and tryptophan showed moderate mutagenicity while histidine and histamine did not show any mutagenicity. Fourteen indole derivatives of tryptophan metabolites in animals or plants (each 10 mM) were treated with 100 mM nitrite at pH 3. All indole derivatives except isatin showed mutagenicity without metabolic activation, lndole acetate, indole pyruvate, indole-3-acetonitrile, indole, 5hydroxytryptamine and tryptamine showed strong mutagenicity (> 103 revertants//~mole). Indole aldehyde, 5-methoxyindole acetate, indole acetaldehyde, indole acetamide and tryptophan showed moderate mutagenicity (up to 102 revertants/#mole). 5-Hydroxyindole acetate and indole lactate showed weak mutagenicity. Mutagens were possibly formed endogenously by the reaction of tryptophan metabolites and nitrite in the body.