273 5,6-dihydro-2H-pyran-2-one, esculetin, and 4methylesculetin had inhibitory effects on 4NQOinduced mutagenesis in WP2S and 4NQO- or MNNG-induced mutagenesis in WP2. The number of Trp + revertant colonies decreased as the concentration of the lactones increased. The lactones were not toxic to the cells within the concentration tested.
27 Kuroda, Y., Laboratory of Phenogenetics, National Institute of Genetics, Mishima, Shizuoka 411 (Japan) Antimutagenic activity of vitamin C in cultured mammalian cells Vitamin C had a marked effect in reducing 6-thioguanine (6TG)-resistant mutations induced by ethyl methanesulfonate (EMS) in Chinese hamster V79 cells. The cells were treated with EMS and vitamin C at various concentrations for 3 h, cultured for 6 days for the mutation expression, and replated in selective medium containing 0.5 # g / m l 6TG. The number of 6TG-resistant colonies formed was scored. Vitamin C alone had no detectable effect on cell survival at concentrations of less than 100 btg/ml. On the other hand, EMS had a cytotoxic effect, showing an LDs0 of 541 /~g/ml. In the presence of vitamin C, the cytotoxic effect of EMS decreased markedly, resulting in an LDs0 of 944 # g / m l . EMS had a strong activity in inducing the 6TG r mutations. At a concentration of 1000/~g/ml, EMS induced 6TG r at a frequency of 88/105 survivors. In the presence of vitamin C, the frequency of mutations induced by EMS became about one fourth of that obtained without vitamin C. It was suggested that vitamin C may have an antimutagenic activity on V79 cells by some mechanisms including the inactivation of mutagens or the enhancement of the repair activity of cells.
28 Masubuchi, Y., T. Matunaga, S. Fujita and T. Suzuki, Department of Biopharmaceutics, Faculty
of Pharmaceutical Sciences, Chiba University, Chiba 260 (Japan) Modifications of the mutagenic activation of carcinogens by a lipstick azo dye Chemical carcinogenesis is prevented by sudan III, a lipophilic azo "dye used for lipstick coloring (Huggins et al., 1978, Proc. Natl. Acad. Sci. (U.S.A.)). We observed, however, that the benzo[a]pyrene (BP) mutagenicity in the Ames test was markedly higher when $9 from rats pretreated with sudan III was used than when $9 from control rats was used. Sudan III caused increases of both the A H H and the cytochrome P-448 activities in the $9. The effect of other azo compounds on the metabolic activation of BP was also investigated. Among these azo dyes, those which induced A H H activity increased the BP mutagenicity. However, these azo dyes including sudan III also induced UDP-glucuronyltransferase (UDPGT) and glutathione-S-transferase (GST) activities which can detoxify active metabolites of BP. As expected, the addition of UDP-glucuronic acid and reduced glutathione, cofactors of U D P G T and GST respectively, to these $9 fractions suppressed the increase in mutagenicity of BP. Similar effects were obtained when we used Trp-P-1 and Trp-P-2 as mutagens.
29 Matsuoka, A., T. Sofuni and M. Ishidate Jr., Division of Mutagenesis, National Institute of Hygienic Sciences, Tokyo 158 (Japan) Effect of surfactants on the induction of chromosomal aberrations in Chinese hamster cells in culture The effect of non-ionic surfactants on the induction of chromosomal aberrations by wellknown clastogens was investigated using a Chinese hamster cell line (CHL). The cells were treated with 3 carcinogens; dimethylnitrosamine (DMN), benzo[a]pyrene (B[a]P) or aniline, in the presence of rat liver $9 mix for their metabolic activation. CMC-sodium or Triton X-100 was used as a surfactant and added to the reaction mixture. The
addition of CMC-sodium increased 1.5-2 times the frequency of chromosomal aberrations induced by DMN. A similar effect was also observed with aniline. The induction of chromosomal aberrations by B[a]P was remarkably enhanced by the addition of Triton X-100. All these surfactants themselves showed no clastogenic activity at the dose used in these experiments. The effect of the surfactants on the enzyme activity of the $9 was also examined. Triton X-100 and CMC-sodium enhanced A H H activity and D M N demethylase or aniline hydroxylase, respectively. These findings indicate that the enhancement of chromosomal aberrations is partly due to the modification of metabolic activity induced by such surfactants.
30 Michi-ue, A., S. Arimoto, H. Kobayashi and H. Hayatsu, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700 (Japan) Analysis of complex formation between mutagens and blue cotton Absorbent cotton bearing covalently bound copper phthalocyanine trisulfonate (blue cotton) has been used for adsorbing frameshift-type mutagens from crude environmental materials. The underlying mechanism for this adsorption has been considered to be a complex formation between the multi-tinged compounds and the copper phthalocyanine nucleus. The adsorption of 9-amino,acridine, 3-amino-l-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), quinacrine, 2-aminofluorene ~nd 2acetylaminofluorene to blue cotton was analyzed. The adsorption in sodium phosphate buffer at pH 7.4 was quantitated by measuring ultraviolet absorption of the compounds in the solution. The adsorption extents as a function of the amount of blue cotton used were determined for individual compounds, and the results were analyzed by use of the Langmuir equation. All of the 5 compounds studied formed one-to-one complexes with the copper phthalocyanine trisulfonate on the cotton, and the dissociation constants were in the range 10-5_10 6 M.
31 Morimoto, K., K. Miura, A. Koizumi and H. Watabe 1, Department of Public Health, University of Tokyo, Bunkyo, Tokyo 113 and 1Ome Research Laboratory, Tobishi Pharmaceutical Co. Ltd., Ome, Tokyo 198 (Japan) Additive sister-chromatid exchange (SCE) response in human lymphocytes in exposure to a combination regimen of mitomycin C (MMC) and 4-nitroquinoline 1-oxide (4NQO) MMC and 4NQO have been known to produce almost completely different damages in chromosomal DNA. As a typical model of combined effects of DNA-damaging muta/carcinogens, the effect of simultaneous administration of these two agents on induction of SCE was investigated. Maximum SCE non-inducing dose (MND) and SCE-doubling dose (DBD) were calculated from dose-response curves with these agents. Human lymphocytes were then exposed to MND or DBD of MMC and various concentrations of 4NQO, or to MND or DBD of 4NQO and various concentrations of MMC. The data clearly indicate that the response in SCE induced by these combined treatment regimens is additive.
32 Muramatsu, M., and T. Matsushima, Department of Molecular Oncology, Institute of Medical Science, University of Tokyo, Tokyo 108 (Japan) Metabolic activation systems for hydroxyl derivatives of anthraquinone and xanthone Hydroxyl derivatives of anthraquinone and xanthone were mutagenic in S. typhimurium TA2637 in the presence of $9 mix. Anthrarufin (1,5-dihydroxy-anthraquinone) and gentisin (1,7dihydroxy-3-methoxy-xanthone) became mutagenic on metabolic activation with microsome (Ms) mix prepared from the liver of SD rats pretreated with 5,6-benzoflavone. However, the mutagenicities of these compounds activated with the Ms mix were only 50-60% of those that can be observed on activation with $9 mix prepared from the benzoflavone-induced liver. On addition of S105 (post-microsomal supernatant) to the Ms mix, the