Environmental and Molecular Mutagenesis - Legacy Tobacco ...

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on means at 0, 40, and 100 ppb did not overlap . Because the increased
Vfs could have been due to increased in vivo cell cycling, four
conditions were evaf'aated in which the frequency of cycling cells was
determined without In vitro mitogenic stimulation . Benzene exposure did
not stimulate cell cycling . Because the autoradiographic assay does not
permit the recovery of variant cells for confirmation of mutant genotype
these results must be interpreted cautiously . However, they do suggest
that in vivo benzene exposure at low levels may be mutagenic to motLse
spleen lymphocytes . Supported by the Texas Air Control Board .(•vf x 10 )
624
0-VANILLIN ENHANCES MUTAGENESIS INDUCED BY MNNG IN ESCHERICHIA COLI .
K . Watanabe, T . Ohta, T . Kato, M . Watanabe and Y . Shirasu, Institute of Environmental
Toxicology, Suzuki-cho 2-772, Kodaira, Tokyo 187 (Japan)
2-hydroxy-3-methoxybenzaldehyde (o-vanillin), the antimutagenic effect of which has
been reported on mutagenesis induced by 4-nitroquinoline 1-oxide (4NQO) in Escherichia
coli WP2s, enhanced N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced mutagenesis in
the same strain . In order to investigate the mechanism of the enhancing effect of ovanillin
against MNNG-induced mutagenesis in E . coli, we have carried out experiments .
Among 7 derivatives of o-vanillin, 2-hydroxy-3-ethoxybenzaldehyde, o-hydroxybenzaldehyde
and m-methoxybenialdehyde showed an enhancing effect on MNNG-induced
mutagenesis in E . c-o -li WP2s . A remarkable enhancement of mutagenesis provoked by Nmethyl-N-nitrosourea,
a methylating agent, was also observed on semi-enriched minimal
agar plates containing o-vanillin in E . coli WP2s . On the contrary, o-vanillin
suppressed greatly furylfuramide- and 4NQ0-induced mutagenesis and showed a slight
suppressing effect against mutagenesis induced by methylmethanesulfonate, N-ethyl-N'nitro-N-nitrosoguanidine
and N-ethyl-N-nitrosourea . In an investigation employing the
various repair-deficient mutants of E . coli B/r, clear enhancement effects by ovanillin
were observed in wild-type atrain E . coli B/r WP2 and its 4 mutants, WP2s
uvrA, ZA60 recA, ZA12 umuC and ZA160 polA, whereas a weak enhancement was observed in
E. coli ZA180 ada-5, ZA113 alkA and ZA130 alkB, all of which cannot induce the
aZcapEive response o alkyla~fon damage . TFiese results may suggest that o-vanillin
inhibits the inducible adaptive response. •
625
NEW MODIFIED STRAINS OF SALMONELLA TYPHIMURIUM TA98, TA100, VERY SENSITIVE TO
NITROARENES AND AROMATIC AMINES BY CLONING OF ACETYLTRANSFERASE GENE .
M . Watanabe, M . Ishidate, Jr ., and T . Nohmi, National Institute of Hygienic
Sciences, 1-18-1, Kamiyoga, Setagaya-ku, Tokyo 158 (Japan)
Acetyl-CoA :N-hydroxyarylamine 0-acetyltransferase ia known ae an enzyme
involved in the intracellular metabolic activation of mutagenic nitroarenes and
aromatic amines . The acetyltranaferase gene of S . t yphimurium TA1538 was cloned
into pBR322 (Biochem . Biophys . Res . Commun . 147, 974-979 (1987)), and the
plasmid harboring the gene (pYG219) was introduced into TA98 and TA100 . The
resulting strains, YG1024 (- TA98(pYG219)) and YG1029 (= TA100(pYG219)), had a
higher isoniazid- and 2-aminofluorene-N-acetyltraneferaee activity 100 timee
more than the original strain, TA1538(pBR322) . They showed an extremely high
mutagenic response to 2-nitrofluorene, 1,8-dinitropyrene, Glu-P-1(+S9) and 2aminoanthracene(+S9)
. The YG1024 was more sensitive to these chemicals than
TA1538/1,8-DNP(pYG121 or 122) strains which we previously established, since the
YG1024 has pKM101 and more acetyltransferase activity . These results indicate
that the new strains are useful for the detection of mutagenic nitroarenes and
aromatic amines .
This work was supported by a Grant-in-Aid from Japan Health Sciences Foundation .
626
NITROARENE SENSITIVE SALMONELLA TYPHIMURIUM STRAINS YG1021 AND YG1026 WITH A
HIGH NITROREDUCTASE ACTIVITY, DERIVED FROM TA98 AND TA100, RESPECTIVELY .
M . Watanabe, M . Ishidate, Jr ., and T . Nohmi, National Institute of Hygienic
Sciences, 1-18-1, Kamiyoga, Setagaya-ku, Tokyo 158 (Japan)
"Classical nitroreductaae" is known as an enzyme involved in the
intracellular metabolic activation of mutagenic nitroarenes . The nitro :eductase
gene of Salmonella t himurium TA1538 was cloned into pBR322 (Biochem . Biophys .
Res . Commun . 147, 974-979 1987)), and the plasmid harboring the gene (pYG216)
was introduced into TA98 and TA100 . The resulting strains, YG1021 (-
TA98(pYG216)) and YG1026 (- TA100(pYG216)), had about 50 times higher
nitrofurazone-reductase activity than TA1538 containing pBR322, and were
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
•
1989 EMS Abstracts 215
Notes