P XV.11 Dose dependent change in the mutation spectrum of the lacI transgene isolated from Big Blue™″ mice subchronically treated with 4-chloro-o-phenylenediamine

SI48

S-XV: Transgenic model for studying environmental mutagenesis

Ip Xv.91

DImethylnitrosamine and chloroform Induced mutagenic profiles In lad transgenic B6C3F1 mice over 180 days

Byron Butterworth, Catherine Sprankle, Michael Templin, Alex Constan, Douglas Wolf, Linda Pluta, Brian Wong, Leslie Recio. CIlT, Research Triangle Park, NC 27709, USA Chloroform appears to induce cancer via a nongenotoxic-cytotoxic mode of action. The purpose of this study was to examine extended exposure periods to detect either direct or secondary mutagenic events. Female B6C3FI lacl mice were exposed daily for 6 hr/day to 0, 10, 30, or 90 ppm chloroform by inhalation, representing nonhepatotoxic, borderline, or hepatotoxic chlorofonn atmospheres. Time points were 10, 30, 90, and 180 days. No increases in mutant frequency were observed with chloroform, consistent with a lack of DNA reactivity. DNA alterations secondary to toxicity either did not occur or were of a type not detectable by this assay such as double-stranded breaks or large deletions. Mice were treated with daily doses of 2, 4, or 8 mglkg of the DNA-reactive mutagen dimethylnitrosamine (DMN) by gavage for 4 days and then held for analysis. Mice receiving 8 mglkg DMN only survived for a few days, but exhibited a 5-fold increase over control mutant frequency. The 2 and 4 mglkg DMN groups exhibited a 2· and 3-fold increase over control mutant frequencies, respectively, that remained elevated for 10 through 180 days. Thus, following the initial induction, no selective mutation amplification or loss was seen for this extended period oftime.

4-Chloro-o-phenylenediamine (4-C-o-PDA) is a mouse liver carcinogen. In a previous study 4-C-o-PDA weakly increased the lacl mutant frequency in the liver of female Big BlueT"" mice, after short tenn treatment However, no significant changes in the mutation spectrum could be detected. In the present study the test compound was given to male and female Big BlueT"" mice 8ubchronically in the diet for 26 weeks. at doses of: 0, SOOO and 10000 ppm and the lacl mutants were isolated from the liver tissue. In both the low and the high dose groups a clear dose-dependent increase in the mutant frequencies was observed for both sexes, when compared with the controls. A representative number of these mutants have been analysed by DNA sequencing. The major change observed in the lacl mutation spectrum was a significant dose-dependent increase in G:C to T:A transversions by factors of 2.I9 (males) and 4.0 (females) in the low dose group and by factors on.59 (males) and S.07 (females) in the high dose group. In conclusion, 4-C-o-PDA is strongly mutagenic and specifically induces G:C to T:A transversions in a dose-dependent manner in the liver of mice treated subchronically for 26 weeks. Keyword(s): 4-Chloro-o-phenylenediamine; lacl transgenic Big Blue™" mice; G:C to T:A transversions

Ip XV,121

Detection of qUinoline-Induced mutation In the lacZ transgenic mouse

Keyword(s): chlorofonn; lacl mice; nongenotoxic carcinogens

Yuko Miyata I, Ken-ichi Saeki I, Yutaka Kawazoe", Takayoshi Suzuki' Makoto Hayashi', Toshio Sofuni'. 1Faculty of Pharmaceutical Sciellces: Naguya City University, Japan; 2 National Instinue ofHealth Sciences. Tokyo,

Ip Xv.t 01

Japan

Quantitative and molecular analysis of DMBA-Induced mutations In the model BlueRat™": Comparison of mutagenesis In the transgene lacl with the endogenous gene

hprt Daniel A. Casciano, Robert H. Heflich, Anane Aidoo, Mugimane G. Manjanatha. NCTR. Jefferson, AR 72079, USA The rodent mammary carcinogen, DMBA, was shown to be a potent ill viuo mutagen at the hprt locus in female Sprague-Dawley splenic lymphocytes exposed to doses resulting in tumors. Similar DNA adducts were detected in the surrogate lymphocytes and the target organ and sequence analysis of hpn mutants indicated that the mutational spectra reflected changes at nucleoside bases targeted by DMBA. The more resistant strain, F344, displayed similar dose- and time-dependent increases in hprt mutant frequencies, except higher doses were required to observe the response. When BlueRat™" was exposed to doses similar to the non-transgenic NCTR F344 strain, a lower mutant frequency was observed. This was most clearly seen with the 75 and 130 mglkg doses where the time course of mutant frequency was similar in the two rat strains. Two-way ANOVA tests of these data indicate the overall responses in BlueRat"'" and F344 animals were significantly different (p < 0.00 I), and pairwise comparisons performed using StudentNewman-Kauls test found sigmficant differences between the BlueRat™" and F344 responses at some time-dose combinations. ANOVA also indicated a significant difference (p < 0.05) between the overall BlueRat™" and F344 responses in the vehicle control groups, but in this case the transgenic ~imals produced the higher response. Although the kinetics and expression time for hprt were similar in the two strains, preliminary data from the 130 mglkg dose show that lacl spleen cell mutant frequency reached a plateau at 6 weeks post exposure and remains at that level to at least 14 weeks post exposure. Keyword(s): LACI; HPRT; Mutagenesis

Ip Xv.ttl

Quinoline, an aza-analog of naphthalene, has potent carcinogenicity in the liver of rats and mice in spite of its simple molecular structure. In order to confirm the possibility that cancer induction may be initiated by mutational DNA lesions induced by quinoline or its metabolites, we evaluated the mutagenicity of quinoline in an 10 VIVO mutation assay system using the lacZ-transgenic mouse (MutaTM Mouse). Mice were i.p. injected with SO mglkglday of quinoline for four consecutive days and the lacZ mutant frequency (MF) of DNA samples extracted from the liver, kidney, lung, and spleen was determined by posinve selection after a 14.
Ip Xv.t31

Role of DNA-adduct formation and cell proliferation In the Induction of gene mutations by 5,9-dlmethyl_ dlbenzoearbazole In Muta™"Mouse liver

Francoise Tombolan l .' , Dominique Brault", Dominique Renault", Fran~ois Perin 3 , Odette Perin-Roussel", Daniele Taras3 , Veronique Thybaud l • 1 RhOlle-Poulenc Rorer. Drug Safety Department, rilry sur Seine, France; 2CNRS UPR 42, Y'dlejuif, France; Jlnstitut Curie-Biologic, Centre Unioer-

sitaire, Orsay, France Dose dependent change In the mutation spectrum of the locI transgene Isolated from Big Blue™" mice subchronIcally treated with 4-ehloro-o-phenylenedlamlne

Jaime Crespo-Perez, Franziska Locher, Tracey Swingler, Laura Wilson, Sandra Steiner, Willi Suter. Frank Staedtler. Nooartis Pharma AG, Preclinical Safety, TaxicoJogylPalhology, CH-4002 Basle, Switzerlalld

5,9-dimelhyl-dibenzocarbazole (DMDBC) is a synthetic derivative of the environmental pollutant, dibenzo[c,g)carbazole. It is a potent genotoxic carcinogen showing an exceptional tropism for mouse liver. Using the positive selection Muta™"Mouse model, Lacz mutant frequency was measured in the liver 28 days after a single subcutaneous administration of DMDBC at 3 10 30 and 90 mglkg. Mutant frequency (MF) remained low at 3 and 10 m~~