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Jay I. Goodman - One of the best experts on this subject based on the ideXlab platform.
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comparison of effect of tumor promoter treatments on dna methylation status and gene expression in B6C3F1 and c57bl 6 Mouse liver and in B6C3F1 Mouse liver tumors
Molecular Carcinogenesis, 1997Co-Authors: Jennifer L. Counts, Michael R Mcclain, Jay I. GoodmanAbstract:The effects of different liver tumor-promoting treatments (i.e., a choline-devoid, methionine-deficient (CMD) diet, phenobarbital (PB), or both) on Ha-ras and raf methylation status and expression were determined in Mouse strains with different susceptibilities to liver tumor formation: the relatively sensitive B6C3F1 and the relatively resistant C57BL/6. Additionally, B6C3F1 Mouse liver tumors, spontaneous or PB induced, were assessed for alterations in global DNA methylation status and expression of Ha-ras and raf. The CMD diet led to hypomethylation of Ha-ras and raf after 12 wk of administration in B6C3F1 and C57BL/6 mice. At this early phase of tumor promotion, the frequency of increased expression of both Ha-ras and raf mRNAs was higher in the B6C3F1 but not the C57BL/6 mice. This is a mechanism that may, in part, underlie the heightened sensitivity of the B6C3F1 Mouse to liver tumorigenesis. Subpopulations of B6C3F1 Mouse liver tumors displayed altered global methylation status, with both hypomethylation and hypermethylation evident. Carcinomas were significantly more hypomethylated than adenomas. The level of raf mRNA was not changed in spontaneous or PB-induced B6C3F1 Mouse liver tumors. Increased expression of Ha-ras was evident in some spontaneous B6C3F1 liver tumors and in most of the PB-induced liver tumors. These experiments support the concept that altered DNA methylation plays a key role in tumorigenesis and indicate that the high propensity of the B6C3F1 mice to liver tumorigenesis may be due, in part, to a decreased ability to maintain normal methylation status.
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Comparison of effect of tumor promoter treatments on DNA methylation status and gene expression in B6C3F1 and C57BL/6 Mouse liver and in B6C3F1 Mouse liver tumors
Molecular carcinogenesis, 1997Co-Authors: Jennifer L. Counts, R. Michael Mcclain, Jay I. GoodmanAbstract:The effects of different liver tumor-promoting treatments (i.e., a choline-devoid, methionine-deficient (CMD) diet, phenobarbital (PB), or both) on Ha-ras and raf methylation status and expression were determined in Mouse strains with different susceptibilities to liver tumor formation: the relatively sensitive B6C3F1 and the relatively resistant C57BL/6. Additionally, B6C3F1 Mouse liver tumors, spontaneous or PB induced, were assessed for alterations in global DNA methylation status and expression of Ha-ras and raf. The CMD diet led to hypomethylation of Ha-ras and raf after 12 wk of administration in B6C3F1 and C57BL/6 mice. At this early phase of tumor promotion, the frequency of increased expression of both Ha-ras and raf mRNAs was higher in the B6C3F1 but not the C57BL/6 mice. This is a mechanism that may, in part, underlie the heightened sensitivity of the B6C3F1 Mouse to liver tumorigenesis. Subpopulations of B6C3F1 Mouse liver tumors displayed altered global methylation status, with both hypomethylation and hypermethylation evident. Carcinomas were significantly more hypomethylated than adenomas. The level of raf mRNA was not changed in spontaneous or PB-induced B6C3F1 Mouse liver tumors. Increased expression of Ha-ras was evident in some spontaneous B6C3F1 liver tumors and in most of the PB-induced liver tumors. These experiments support the concept that altered DNA methylation plays a key role in tumorigenesis and indicate that the high propensity of the B6C3F1 mice to liver tumorigenesis may be due, in part, to a decreased ability to maintain normal methylation status.
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Cell proliferation and global methylation status changes in Mouse liver after phenobarbital and/or choline-devoid, methionine- deficient diet administration
Carcinogenesis, 1996Co-Authors: Jennifer L. Counts, R. Michael Mcclain, Juan I. Sarmiento, Margaret L. Harbison, J.c. Downing, Jay I. GoodmanAbstract:^To whom correspondence should be addressed Our laboratory is testing the hypothesis that hypomethylation of DNA [a decreased content of 5-methylcytos ine (5MeC) compared with cytosine] facilitates aberrant oncogene expression involved in tumorigenesis , using a model system of Mouse strains with differing susceptibilities to liver tumorigenesis. The B6C3F1 (C57BL/6 x C3H/He) Mouse serves as the relatively susceptible strain and C57BL/ 6 serves as the relatively resistant strain. Phenobarbital (PB) and/or administration of a choline-devoid, methioninedeficient diet (CMD) were employed as non-genotoxic hepatocarcinogens. We have examined hepatocyte and nonhepatocyte proliferation in conjunction with an assessment of global methylation changes in liver DNA of B6C3F1 and C57BL/6 mice following these promoter treatments. Bromodeoxyuridine incorporation into DNA, used to measure cell proliferation indirectly, was visualized by immunohistochemistry and quantified by a Macintosh-based image analysis system. Increased hepatocyte proliferation was demonstrated following all three treatments. This increase was larger in C57BL/6 (the relatively resistant strain) as compared with B6C3F1. In contrast, global hypomethylation was evident to a larger extent in the B6C3F1 Mouse, as compared with C57BL/6. PB led to hypomethylati on (>20% decrease as compared with controls) at weeks 1, 2 and 4 in B6C3F1, but not in C57BL/6 at the same time points. CMD diet administration led to hypomethylati on in both strains. At week 1, 21 and 9% decreases in global methylation status were observed in B6C3F1 and C57BL/ 6 respectively. Evaluation of these data suggests that the heightened sensitivity of the B6C3F1 Mouse compared with the C57BL/6 is due, in part, to a decreased capacity for, or fidelity of, maintaining normal methylation status. The relatively resistant strain is better able to maintain the normal methylation status of DNA in the face of a higher level of cell proliferation.
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Alterations in the methylation status and expression of the raf oncogene in phenobarbital-induced and spontaneous B6C3F1 Mouse liver tumors.
Molecular carcinogenesis, 1994Co-Authors: Jay I. GoodmanAbstract:The liver tumor-prone B6C3F1 Mouse (C57BL/6 ♂ × C3H/He♀), in conjunction with the more susceptible C3H/He paternal strain and the resistant C57BL/6 maternal strain, is an excellent model for studying the mechanisms involved in carcinogenesis. The study reported here indicated that the B6C3F1 Mouse inherited a maternal raf allele containing a methylated site not present in the paternal allele. Seven days after partial hepatectomy or after administration of a promoting dose of phenobarbital (PB) for 14 d; raf in B6C3F1 Mouse liver was hypomethylated. The additional methylated site in the allele inherited from C57BL/6 was not maintained. The methylation status of raf in the liver of the C57BL/6 Mouse was not affected by PB treatment. This indicates that the B6C3F1 Mouse is less capable of maintaining methylation of raf than the C57BL/6 strain is. In both PB-induced and spontaneous B6C3F1 liver tumors, raf was hypomethylated in a nonrandom fashion. The level of raf mRNA increased in seven of 10 PB-induced tumors but in only one of five spontaneous tumors, whereas the level of Ha-ras mRNA increased in nine of 10 PB-induced tumors and in four of five spontaneous tumors. The results of our investigation (a) support the hypothesis that hypomethylation of DNA is a nongenotoxic mechanism involved in tumorigenesis, (b) support the notion that PB promotes liver tumors that develop along a pathway different from that leading to spontaneous tumors, and (c) indicate that differences in DNA methylation between C57BL/6 and B6C3F1 mice could, in part, account for the unusually high tendency of the latter strain to develop liver tumors. © 1994 Wiley-Liss, Inc.
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Differential DNase I hypersensitivity of ras oncogenes in B6C3F1, C3H/He, and C57BL/6 Mouse liver.
Journal of toxicology and environmental health, 1991Co-Authors: Roseann L. Vorce, Jay I. GoodmanAbstract:The male hybrid B6C3F1 Mouse exhibits a 30% spontaneous hepatoma incidence, whereas the paternal C3H/He strain and the maternal C57BL/6 strain exhibit a 60% and a negligible incidence, respectively. In addition, both male and female B6C3F1 mice are extremely sensitive to chemical induction of hepatocarcinogenesis. The Ha-ras, Ki-ras, and myc oncogenes have been implicated in a variety of solid tumors. Specifically, Ha- and, less frequently, Ki-ras have been reported to be activated in B6C3F1 Mouse liver tumors. The objective of this study was to examine a possible point of transcriptional control of Ha-ras, Ki-ras, and myc in all three Mouse strains, our hypothesis being that these oncogenes may be primed for expression in the nascent liver of those strains exhibiting a high spontaneous hepatoma incidence. A positive correlation has been established between gene expression and the presence of DNase I hypersensitive sites. DNase I hypersensitive sites were observed in the Ha-ras and myc oncogenes in the three Mouse strains. However, Ha-ras appears to possess an additional site in B6C3F1 and C3H/He as compared to C57BL/6. Similarly, the Ki-ras oncogene exhibited a DNase I hypersensitive site only in B6C3F1 and C3H/He Mouse liver. These results indicate that the hepatoma-prone strains (B6C3F1 and C3H/He) may have a greater potential for Ha- and Ki-ras expression than does the non-hepatoma-prone strain (C57BL/6).
Sharon A. Leavitt - One of the best experts on this subject based on the ideXlab platform.
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Induction of mutations by 2-acetylaminofluorene in lad transgenic B6C3F1 Mouse liver
Mutagenesis, 1998Co-Authors: Jeffrey A. Ross, Sharon A. LeavittAbstract:Mutations induced in liver cells by the hepatocarcinogen 2-acetylaminofluorene (2-AAF) were characterized after i.p. administration on 4 consecutive days at 100 mg/kg per injection in male B6C3F1 Big Blue transgenic mice that harbored the Escherichia coli lacI reporter gene. Animals were sacrificed at 5, 10 or 60 weeks following the last injection, livers removed and DNA packaged in vitro into bacteriophage lambda particles. The bacteriophage were assayed for lacI function by plating on E. coli in the presence of X-gal. Approximately 3 x 10(5) plaques were assayed per animal. Solvent-treated control mice exhibited a slight increase in mutant frequency over time, from 3.93 x 10(-5) at 5 weeks to 5.02 x 10(-5) at 60 weeks. In contrast, treatment with 2-AAF yielded an approximately 2-fold increase in mutant frequency at 5 and 10 weeks after treatment relative to controls, with frequencies of 8.13 x 10(-5) and 7.43 x 10(-5) respectively. However, by 60 weeks post-treatment the mutant frequency was not significantly increased over concurrent controls. Similar to results in other systems, 2-AAF induced predominantly single base changes targeted to G:C base pairs, primarily G:C-->T:A transversions (27%). In contrast to results in other bacterial and eukaryotic systems, no deletions were observed among the 2-AAF-induced mutations and the 4 base hot spot deletion that is frequently observed in lacI in E. coli was not observed in this system, suggesting that the lacI transgene may be relatively refractory to frameshift mutations in vivo in the Mouse.
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Assessment of the mutagenicity of dichloroacetic acid in lacI transgenic B6C3F1 Mouse liver.
Carcinogenesis, 1997Co-Authors: Sharon A. Leavitt, Anthony B. Deangelo, Michael H. George, Jeffrey RossAbstract:Dichloroacetic acid (DCA) is a chlorination byproduct found in finished drinking water. When administered in drinking water this chemical has been shown to produce hepatocellular adenomas and carcinomas in B6C3F1 mice over the animal's lifetime. In this study, we investigated whether mutant frequencies were increased in Mouse liver using treatment protocols that yielded significant tumor induction. DCA was administered continuously at either 1.0 or 3.5 g/l in drinking water to male transgenic B6C3F1 mice harboring the bacterial lacI gene. Groups of five or six animals were killed at 4, 10 or 60 weeks and livers removed. At both 4 and 10 weeks of treatment, there was no significant difference in mutant frequency between the treated and control animals at either dose level. At 60 weeks, mice treated with 1.0 g/l DCA showed a 1.3-fold increase in mutant frequency over concurrent controls (P = 0.05). Mice treated with 3.5 g/l DCA for 60 weeks had a 2.3-fold increase in mutant frequency over the concurrent controls (P = 0.002). The mutation spectrum recovered from mice treated with 3.5 g/l DCA for 60 weeks contained G:C-->A:T transitions (32.79%) and G:C-->T:A transversions (21.31%). In contrast, G:C-->A:T transitions comprised 53.19% of the recovered mutants among control animals. Although only 19.15% of mutations among the controls were at T:A sites, 32.79% of the mutations from DCA-treated animals were at T:A sites. This is consistent with the previous observation that the proportion of mutations at T:A sites in codon 61 of the H-ras gene was increased in DCA-induced liver tumors in B6C3F1 mice. The present study demonstrates DCA-associated mutagenicity in the Mouse liver under conditions in which DCA produces hepatic tumors.
F. F. Kadlubar - One of the best experts on this subject based on the ideXlab platform.
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Formation of malondialdehyde-modified 2'-deoxyguanosinyl adduct from metabolism of chloral hydrate by Mouse liver microsomes.
Biochemical and biophysical research communications, 1995Co-Authors: F. F. KadlubarAbstract:We previously reported that metabolism of chloral hydrate (CH), a widely used sedative and hypnotic, by male B6C3F1 Mouse liver microsomes resulted in lipid peroxidation, producing the tumorigen malondialdehyde (MDA). Now we have found that incubation of CH in the presence of calf thymus DNA resulted in the formation of an MDA-modified DNA adduct as detected by 32P-postlabeling analysis. Similar results were obtained from incubation of trichloroacetic acid and trichloroethanol, both metabolites of CH.
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Hepatic metabolism of chloral hydrate to free radical(s) and induction of lipid peroxidation.
Biochemical and biophysical research communications, 1994Co-Authors: Tit-yee Wong, F. F. KadlubarAbstract:Metabolism of chloral hydrate by male B6C3F1 Mouse liver microsomes generates free radical intermediate(s) as evidenced by electron spin resonance spectroscopic analysis. The subsequent induction of endogenous lipid peroxidation was shown by analysis of the resulting products with high-pressure liquid chromatography. Chloral hydrate was found mutagenic in Salmonella typhimurium strain TA104. Both lipid peroxidation and mutagenicity were efficiently inhibited by free radical scavengers, α-tocopherol and menadione.
Bradley J. Collins - One of the best experts on this subject based on the ideXlab platform.
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Validation of a Method for the Determination of Total Chromium in Rat Feces by Inductively Coupled Plasma Optical Emission Spectrometry
Analytical letters, 2009Co-Authors: Keith E. Levine, Reshan A. Fernando, Matthew D. Stout, Glenn T. Ross, Amal S. Essader, Jason M. Perlmutter, Peter M. Grohse, Michelle Lang, Bradley J. CollinsAbstract:The validation of a method for the determination of total chromium in Fischer-344 rat feces by inductively coupled plasma optical emission spectrometry following a rapid, atmospheric-pressure microwave digestion is described. The performance of the method was evaluated over the concentration range of 5.00 to 200 μg Cr/g feces. Data for method linearity, accuracy, precision, digest stability, and storage stability are presented along with limit of detection and limit of quantitation data. Data from a cross-validation method for B6C3F1 Mouse feces are also presented. Following validation, the method was applied to analyze samples collected in support of two chronic toxicological investigations.
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Validation and application of a method for the determination of total chromium in rat tissues by inductively coupled plasma mass spectrometry.
Archives of environmental contamination and toxicology, 2009Co-Authors: Keith E. Levine, Reshan A. Fernando, Matthew D. Stout, Glenn T. Ross, Amal S. Essader, Peter M. Grohse, Frank X. Weber, Lisa S. Milstein, Michelle J. Hooth, Bradley J. CollinsAbstract:The validation of a method for the determination of chromium (Cr) in F-344/N rat tissues by inductively coupled plasma-mass spectrometry is described. Samples were analyzed after a rapid, open-vessel microwave digestion procedure. Performance of the method was evaluated using kidney tissue across a concentration range of 0.50-5.00 microg Cr/g tissue. Data for method linearity, accuracy, precision, digest stability, and storage stability are presented along with limits of detection and quantitation data. Data from a method cross-validation for B6C3F1 Mouse kidney tissue are also presented. After validation, the method was applied to analyze samples collected in support of two chronic toxicity and carcinogenesis studies conducted by the National Toxicology Program.
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Determination of lovastatin hydroxy acid in female B6C3F1 Mouse serum.
Journal of analytical toxicology, 2008Co-Authors: Jon W. Lodge, Brenda L. Fletcher, Sherri S. Brown, Angela J. Parham, Reshan A. Fernando, Bradley J. CollinsAbstract:A liquid chromatographic-mass spectrometricmethod for the determination of lovastatin hydroxy acid in female B6C3F 1 Mouse serum was developed for use in supporting toxicokinetic studies of animals dosed with the cholesterol lowering agent lovastatin. The method does not require an extensive sample cleanup and shows good correlation between serum matrix standards and solvent standards. The method was validated and used to analyze serum samples from a preliminary dose level range-finding study. The method was validated for a concentration range of approximately 1.0 to 100 ng/mL in serum, and linearity was verified to -2000 ng/mL. The stability of sample extracts was determined under various storage conditions and the stability of serum samples stored frozen was determined over a period of seven weeks. During the course of analyzing the animal samples, the serum was monitored for the presence of lovastatin not hydrolyzed to the hydroxy acid, but no attempt was made to quantify lovastatin. No unhydrolyzed lovastatin was noted in any of the serum samples from animals dosed with lovastatin.
Leslie Recio - One of the best experts on this subject based on the ideXlab platform.
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acb pcr measurement of spontaneous and furan induced h ras codon 61 caa to cta and caa to aaa mutation in B6C3F1 Mouse liver
Environmental and Molecular Mutagenesis, 2013Co-Authors: Malathi Banda, Leslie Recio, Barbara L ParsonsAbstract:Furan is a rodent liver carcinogen, but the mode of action for furan hepatocarcinogenicity is unclear. H-ras codon 61 mutations have been detected in spontaneous liver tumors of B6C3F1 mice, and the fraction of liver tumors carrying H-ras codon 61 CAA to AAA mutation increased in furan-treated mice. Allele-specific competitive blocker PCR (ACB-PCR) has been used previously to quantify early, carcinogen-induced increases in tumor-associated mutations. The present pilot study investigated whether furan drives clonal expansion of pre-existing H-ras mutant cells in B6C3F1 Mouse liver. H-ras codon 61 CAA to CTA and CAA to AAA mutations were measured in DNA isolated from liver tissue of female mice treated with 0, 1, 2, 4, or 8 mg furan/kg body weight, five days per week for three weeks, using five mice per treatment group. Spontaneous levels of mutation were low, with two of five control mice having an H-ras codon 61 CTA or AAA mutant fraction (MF) greater than 10(-5) . Several furan-treated mice had H-ras codon 61 AAA or CTA MFs greater than those measured in control mice and lower bound estimates of induced MF were calculated. However, no statistically-significant differences were observed between treatment groups. Therefore, while sustained exposure to furan is carcinogenic, at the early stage of carcinogenesis examined in this study (three weeks), there was not a significant expansion of H-ras mutant cells.
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ACB‐PCR measurement of spontaneous and furan‐induced H‐ras Codon 61 CAA to CTA and CAA to AAA mutation in B6C3F1 Mouse liver
Environmental and molecular mutagenesis, 2013Co-Authors: Malathi Banda, Leslie Recio, Barbara L ParsonsAbstract:Furan is a rodent liver carcinogen, but the mode of action for furan hepatocarcinogenicity is unclear. H-ras codon 61 mutations have been detected in spontaneous liver tumors of B6C3F1 mice, and the fraction of liver tumors carrying H-ras codon 61 CAA to AAA mutation increased in furan-treated mice. Allele-specific competitive blocker PCR (ACB-PCR) has been used previously to quantify early, carcinogen-induced increases in tumor-associated mutations. The present pilot study investigated whether furan drives clonal expansion of pre-existing H-ras mutant cells in B6C3F1 Mouse liver. H-ras codon 61 CAA to CTA and CAA to AAA mutations were measured in DNA isolated from liver tissue of female mice treated with 0, 1, 2, 4, or 8 mg furan/kg body weight, five days per week for three weeks, using five mice per treatment group. Spontaneous levels of mutation were low, with two of five control mice having an H-ras codon 61 CTA or AAA mutant fraction (MF) greater than 10(-5) . Several furan-treated mice had H-ras codon 61 AAA or CTA MFs greater than those measured in control mice and lower bound estimates of induced MF were calculated. However, no statistically-significant differences were observed between treatment groups. Therefore, while sustained exposure to furan is carcinogenic, at the early stage of carcinogenesis examined in this study (three weeks), there was not a significant expansion of H-ras mutant cells.
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Expression and distribution of cytochrome P450 2E1 in B6C3F1 Mouse liver and testes.
Chemico-biological interactions, 1999Co-Authors: Laura N. Healy, Linda J. Pluta, Leslie RecioAbstract:Cytochrome P450 2E1 (CYP2E1) is believed to have a significant role in the bioactivation of 1,3-butadiene (BD) to DNA reactive epoxide metabolites that induce somatic and germ cell genotoxicity in mice. To assess the potential role of in situ bioactivation of BD by Mouse testes for inducing germ cell genotoxicity, the presence of CYP2E1 in testes has been demonstrated by reverse transcriptase-polymerase chain reaction (RT-PCR), immunoprecipitation-Western blotting methods (IP-Western) and immunohistochemistry of tissue sections. Detection of CYP2E1 in the testes was limited to interstitial cells. In liver a known site of BD bioactivation and a positive control tissue used for these studies, a discrete, zonal staining pattern of liver CYP2E1 expression detected by immunohistochemical staining was shown. These results suggest that in situ bioactivation of BD in testes by CYP2E1 may contribute to BD-induced germ cell genotoxicity.
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Determination of mutagenicity in tissues of transgenic mice following exposure to 1,3-butadiene and N-ethyl-N-nitrosourea.
Toxicology and applied pharmacology, 1992Co-Authors: Leslie Recio, Siv M. Osterman-golkar, György A. Csanády, Max J. Turner, Brian Myhr, Owen R. Moss, James A. BondAbstract:Abstract 1,3-Butadiene (BD) is carcinogenic in the B6C3F1 Mouse in multiple organs, including lung and liver. We conducted a study to measure the frequency of BD mutations in Mouse tissues using a transgenic Mouse (Muta Mouse; MM). MM is a BALB c × DBA 2 (CD2F1) Mouse that has a bacteriophage λ shuttle vector with the target gene lacZ integrated into the Mouse genome. Mice were exposed by inhalation to 625 ppm BD (6 hr/day) for 5 days and the lacZ − mutant frequency (mf) was determined in lung, bone marrow, and liver. The lacZ − mf in lung increased twofold above air-exposed control animals, but the bone marrow and liver samples did not exhibit an increase above background. N -ethyl- N -nitrosourea (250 mg/kg ip) was mutagenic in all three tissues examined. Studies on the biotransformation of BD using MM liver microsomes showed that the ratio between the rates of BD bioactivation to BD monoepoxide (BMO) and hydrolysis of BMO by epoxide hydrolases was approximately 40% less than this ratio using B6C3F1 Mouse liver microsomes. Quantitation of adducts of BMO to N-terminal valine in hemoglobin (Hb) in the MM revealed an adduct level of 3.7 pmol/mg globin. Using this value, the predicted Hb adduct level in MM would be approximately one-half of that measured in the B6C3F1 Mouse following similar exposures. These results indicate that BD induces mutations in vivo in a known murine target tissue, but strain differences in the biotransformation of BD should be considered in comparing the susceptibility of transgenic Mouse strains to mutation.