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N J Gooderham

Publications and source records attributed to N J Gooderham.

At least 19 recordsLinked to original sources
PubMed2003

Upregulation of cyclooxygenase-2 is accompanied by increased expression of nuclear factor-kappa B and I kappa B kinase-alpha in human colorectal cancer epithelial cells.

Cyclooxygenase-2 (COX-2) is selectively overexpressed in colorectal tumours. The mechanism of COX-2 induction is not fully understood, but requires de novo messenger RNA and protein synthesis, indicating regulation at the transcriptional level. Sequence analysis of the 5'-flanking region of the COX-2 gene shows two nuclear factor-kappa B (NF-kappa B) sites. Inhibition of this protein in model cell culture systems attenuates COX-2 expression and implies that NF-kappa B plays an important role in COX-2 induction. We measured COX-2, NF-kappa B and I kappa B kinase alpha (IKK alpha) protein expression in matched colonic biopsy samples comprising both nontumour and adjacent tumour tissue from 32 colorectal cancer patients using immunohistochemistry. There was none or very little expression of COX-2, NF-kappa B and IKK alpha in non-neoplastic colon epithelial cells, while the expression of all three of these proteins was significantly increased (P<0.05, Wilcoxon's signed rank test) in adjacent cancerous cells. Moreover, all three proteins were found to be coexpressed in the neoplastic epithelium, with the expression of COX-2 and NF-kappa B highly correlated (Pearson's correlation, P<0.005). There was no apparent correlation between enhanced COX-2, NF-kappa B or IKK alpha expression and tumour Dukes' stages. Our results are compatible with the hypothesis that IKK alpha and NF-kappa B are involved in COX-2 induction in these tumours and the lack of association between COX-2 expression and severity of disease as measured by Dukes' stage is consistent with the proposal that COX-2 expression is an early postinitiation event.

Adult↗
PubMed2001

Effect of cruciferous vegetable consumption on heterocyclic aromatic amine metabolism in man.

The consumption of cooked meat appears to predispose individuals to colonic cancer and heterocyclic aromatic amines (HA), formed during the cooking of meat, have been suggested as aetiological agents. Consumption of cruciferous vegetables is thought to protect against cancer. To study the effect of cruciferous vegetables on heterocyclic aromatic amine metabolism in man, a three-period, dietary intervention study has been carried out with 20 non-smoking Caucasian male subjects consuming cooked meat meals containing known amounts of these carcinogens. A high cruciferous vegetable diet (250 g each of Brussels sprouts and broccoli per day) was maintained during period 2 but such vegetables were excluded from periods 1 and 3. At the end of each period, subjects consumed a cooked meat meal and urinary excretion of the HA 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) was measured. Following a 12 day period of cruciferous vegetable consumption (period 2), induction of hepatic CYP1A2 activity was apparent from changes in the kinetics of caffeine metabolism. Excretion of MeIQx and PhIP in urine at the end of this period of the study was reduced by 23 and 21%, respectively, compared with period 1. This reduction in excretion is probably due to an increase in amine metabolism that might be expected given the observed increase in CYP1A2 activity, since this enzyme has been shown to be primarily responsible for the oxidative activation of MeIQx and PhIP in man. In period 2, urinary mutagenicity was increased relative to period 1 by 52 and 64% in the absence and presence, respectively, of a human liver microsomal activation system, yet no evidence was found of PhIP adduction to lymphocyte DNA, a potential biomarker of the activation process. After another 12 days without cruciferous vegetables (period 3 of the study), the kinetics of caffeine metabolism had returned to original values but excretion of MeIQx and PhIP was still reduced by 17 and 30%, respectively, and urinary mutagenicity (with metabolic activation) was still elevated compared with period 1. This prolonged response of amine metabolism to the cruciferous vegetable diet, shown especially with PhIP, suggests that enzyme systems other than CYP1A2 are involved and affected by a cruciferous vegetable diet.

Adult↗
PubMed2001

Food-derived heterocyclic amine mutagens: variable metabolism and significance to humans.

The cooking of meat has been found to generate compounds that possess extreme mutagenicity when examined in short term tests. This observation led to the isolation and identification of a family of mutagenic chemicals, all of which are heterocyclic amines. These amines are potent bacterial and eukaryotic cell mutagens, and all of those tested have been found to induce tumors in laboratory animals. Metabolic activation of the heterocyclic amines predominantly involves CYP1-mediated N-hydroxylation and then O-esterification by phase II enzymes. In contrast, carbon oxidation, glucuronidation, and sulfation reactions at sites other than the hydroxylamine yield detoxication metabolites. In humans, the activities of these pathways are known to vary between individuals and are likely to influence susceptibility to the genetic toxicity of the heterocyclic amines. Clearly, accurate determination of human exposure to the heterocyclic amines and identification of the key enzyme systems involved and their regulation will be required for rational assessment of the risk and will help devise strategies to reduce such risk.

Amines↗
PubMed2000

Mass spectrometric detection and measurement of N2-(2'-deoxyguanosin-8-yl)PhIP adducts in DNA.

Capillary column gas chromatography-electron-capture mass spectrometry (GC-MS) and microbore liquid chromatography-positive ion electrospray mass spectrometry (LC-MS) have been used to measure the carcinogenic, food-derived, heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) adducted at C-8 of deoxyguanosine in DNA. For GC-MS analysis, PhIP was released from adducted DNA by alkaline hydrolysis and analysed as the di(3,5-bistrifluoromethylbenzyl) derivative, while for LC-MS analysis, the nucleoside N2-(2'-deoxyguanosin-8-yl)PhIP was generated by enzymic digestion of DNA and analysed intact. A deuterated analogue of N2-(2'-deoxyguanosin-8-yl)PhIP was used as an internal standard in both assays, which each had a limit of quantification of 200 pg/500 microg DNA. The two methods were used to analyse DNA extracted from h1A2v2 cells and HCT116 cells that had been exposed to PhIP.

Animals↗
PubMed2000

The food-derived carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine activates S-phase checkpoint and apoptosis, and induces gene mutation in human lymphoblastoid TK6 cells.

The mutagenic heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-blpyridine (PhIP) is formed at parts per billion levels when meat is cooked. It is efficiently absorbed from cooked food and extensively activated to its genotoxic N-hydroxy derivative by human cytochrome P4501A enzymes. It is also a rodent carcinogen. To better understand the genetic toxicity of PhIP, we have examined its effect on the cell cycle and gene mutation frequency using human lymphoblastoid cells (TK6) as a model. Because TK6 cells are unable to activate PhIP, we have cultured the cells in the presence of irradiated Chinese hamster XEMh1A2-MZ cells that have been genetically engineered to express human CYP1A2. Asynchronized TK6 cells were harvested at various times after treatment with PhIP (1.25-10 microg/ml), fixed and stained with propidium iodide for the examination of cell cycle by fluorescence-activated flow cytometry. After 20 h of PhIP treatment, a slight S-phase delay of the cell cycle was observed. Normal cell cycle recovered after the cells were washed and further cultured in the absence of PhIP for 5 days. However, PhIP treatment for 40 h induced a more pronounced S-phase arrest that was accompanied by a decrease in the level of cyclin A, an S-phase cyclin. This was followed by the appearance of a sub-G1 population (indicative of apoptotic cell death), range from 13 to 54% with PhIP concentrations from 1.25 to 10 microg/ml, compared with 5% in the vehicle control. A concomitant increase of mutation frequency at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus, assessed by colony formation assay in the presence of 6-thioguanine, was detected after 40 h-range, 16 to 45 x 10(-6) compared with 12 x 10(-6) in cultures without PhIP. In G1-enriched cell populations (synchronized culture), although PhIP induced S-phase delay, the induction of sub-G1 cells was substantially decreased. Our studies show that in TK6 cells, PhIP activates S-phase checkpoint, yet eludes G1 and G2-M checkpoints, and is accompanied by increased apoptosis and gene mutation. If treatment with PhIP induces similar cellular reactions in vivo, then activation of S-phase checkpoint with avoidance of G1 and G2-M checkpoints could be important factors in PhIP-induced genetic damage and neoplastic disease.

Animals↗
PubMed1999

Nucleosomes bind to cell surface proteoglycans.

Material on the surface of activated T-cells was displaced following incubation with a sulfated polysaccharide, dextrin 2-sulfate (D2S), and purified by anion-exchange chromatography. This revealed a complex comprising histones H2A, H2B, H3, and H4 and DNA fragmented into 180-base pair units characteristic of mono-, di-, tri, and polynucleosomes, a pattern of fragmentation similar to that found in apoptotic cells. An antibody raised against the purified nucleosome preparation bound to the plasma membrane of activated T-cells confirming the surface location of nucleosomes. The interaction of sulfated polysaccharides with nucleosomes was investigated using a biotinylated derivative of D2S. It was found that sulfated polysaccharides bound to nucleosomes via the N termini of histones, especially H2A and H2B. Treatment of T-cells with either heparinase or heparitinase abolished nucleosome binding to plasma membranes. This suggests that nucleosomes are anchored to the surface of T-cells by heparan sulfate proteoglycans through an ionic interaction with the basic N-terminal residues in the histones. Furthermore, nucleosomes bound to the cell surface in this manner are then able to bind other sulfated polysaccharides, such as D2S, heparin, or dextran sulfate, through unoccupied histone N termini forming a complex comprising cell surface heparan sulfate proteoglycans, nucleosomes, and sulfated polysaccharides.

Animals↗
PubMed1999

Interaction of the transactivating protein HIV-1 tat with sulphated polysaccharides.

Endogenous sulphated polysaccharides such as heparin have been shown to inhibit the infectivity of HIV-1 min vitro. However, these naturally occurring polymers, due to extensive microheterogeneity within their structure, are difficult to characterise accurately. In contrast, dextrin can be chemically sulphated to produce a series of compounds sulphated in the 2-, 3-, or 6- position, or in all 3 positions, and the use of these compounds provides an opportunity to investigate the anti-HIV-1 activity of sulphated polysaccharides. The mechanisms whereby sulphated polysaccharides exert their anti-HIV-1 activity have not been fully elucidated. The interaction of recombinant HIV-1 proteins with sulphated polysaccharides was investigated using a biotinylated derivative of dextrin 2-sulphate (D2S) in a solid phase binding system. D2S was found to bind strongly to HIV-1 tat (EC50 = 0.10 microg/mL), less strongly to CD4 (EC50 = 0.33 microg/mL), weakly to HIV-1 vif and gp160, and not at all to HIV-1 gp120 or p24. Other sulphated derivatives of dextrin, i.e. dextrin 3-sulphate, dextrin 6-sulphate and dextrin 2,3,6-trisulphate, as well as heparin and dextran sulphate, were also shown to bind to HIV-1 tat, whereas the unsulphated compound dextrin did not. Binding studies using a series of overlapping peptides representing the complete sequence of HIV-1 tat revealed that D2S bound most strongly to the core domain of HIV-1 tat, although there was also binding to the cysteine-rich domain; both of these regions are important for HIV-1 tat function. In assessing function, HIV-1 tat-mediated transactivation was measured using H938 cells, a cell line that contains the HIV-LTR (long terminal repeat) promoter linked to a chloramphenicol acetyltransferase gene. D2S significantly inhibited HIV-1 tat transactivation in a dose-dependent manner (IC50 = 0.5 microg/mL), whereas dextrin had no effect. The interaction between D2S and HIV-1 tat provides a potential mechanism of HIV-1 inhibition whereby tat is sequestered and its transactivating activity abolished, effectively inhibiting the replication cycle.

Amino Acid Sequence↗
PubMed1999

The mutagenicity of benzo[a]pyrene in mouse small intestine.

We have investigated the mutagenicity of benzo[a]pyrene (B[a]P) in small intestine using the Dlb-1 locus assay in the mouse. Administration of B[a]P by the oral and i.p. routes had markedly different effects on the number of Dlb-I mutations and the pattern of induction of cytochrome P-4501A1 (CYP1A1). In Ahr-responsive animals i.p. injection resulted in marked induction in crypt cells along the length of the small intestine, with some induction in the villus cells. In contrast, after oral administration, CYP1A1 induction was evident only in the villus cells, and this declined distally. The intensity and speed of induction in Ahr-responsive animals was such that the genotoxic effect of a single injection of B[a]P could not be augmented by prior treatment with non-genotoxic inducers such as beta-napthoflavone and TCDD. Oral B[a]P treatment resulted in a decrease in the number of mutations when compared with the i.p. route. Studies in congenic Ahr-non-responsive versus Ahr-responsive mice indicated that induction of CYP1A1 was associated with increased numbers of Dlb-1 mutations. Mutation induction in Ahr-non-responsive mice in the absence of detectable CYP1A1 in either liver or small intestine indicates that an appreciable portion of B[a]P activation to a genotoxin must be by other than a CYP1A1 mediated route. These data show that B[a]P is a potent small intestinal mutagen at the Dlb-1 locus.

Animals↗
PubMed1998

Genetic analysis of PHIP intestinal mutations in MutaMouse.

The mutagenicity of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated in male MutaMouse mice administered 20 mg/kg per o.s. for 4 days and killed 7 days later. Genomic DNA was extracted from liver, kidney and small and large intestine and the mutation frequency (MF) at the lacZ locus was determined using a positive selection assay. Mutant lacZ clones from the intestine were characterized further by direct PCR amplification and DNA sequencing. A total of 57 lacZ mutants from PhIP-treated (40) and untreated (18) mice were analysed. In mutants from the PhIP group, 33% were G:C-->T:A transversions from a total of 65% base substitutions (cf. 17% in the vehicle control group). In untreated control mice, 39% of mutants were G:C-->A:T transitions from a total of 72 % base substitutions (cf. 25 % in the PhIP group). Interestingly, 20% of the PhIP group mutations were due to G:C base pair (-G) deletions (cf. none in controls). This study confirms that PhIP is mutagenic to the intestine of the MutaMouse and induces a spectrum of mutations which are clearly distinct from those spontaneously generated. Also, the PhIP mutation signature in vivo is very similar to that observed for the HPRT and DHFR loci in hamster and human cells in vitro. This suggests that the mutational characteristics of PhIP are well conserved over different reporter genes and between species and that the mutation signature could be of value in molecular epidemiology studies.

Animals↗
PubMed1997

Anti-HIV type 1 activity of sulfated derivatives of dextrin against primary viral isolates of HIV type 1 in lymphocytes and monocyte-derived macrophages.

The anti-HIV-1 activity of sulfated derivatives of dextrin was tested in activated peripheral blood mononuclear cells and in monocyte-derived macrophages using low-passage syncytium-inducing and non-syncytium-inducing primary viral isolates of HIV-1. All four compounds blocked infection in a dose-dependent manner. Dextrin 2-sulfate blocked infection with a 90% inhibitory concentration (IC90) of 69 microg ml(-1). The IC90 for dextrin 3-sulfate was 50 microg ml(-1) and for dextrin 6-sulfate was 14 microg ml(-1). Increasing the number of sulfate groups to three per glucan molecule (dextrin 2-, 3-, and 6-sulfate) did not reduce the IC90 further (13 microg ml(-1)) compared to dextrin 6-sulfate. There was no significant difference in the concentration required to block infection of activated peripheral blood mononuclear cells when compared with monocyte-derived macrophages, irrespective of whether low-passage syncytium-inducing or non-syncytium-inducing primary viral isolates of HIV-1 were used. Dextrin 2-sulfate and dextrin 6-sulfate also reduced the transmission of HIV-1 in experiments performed using peripheral blood mononuclear cells from HIV-1-positive patients by 6- to 251-fold in a limiting dilution tissue culture infectious dose assay. Sulfated dextrins were not toxic to either primary lymphocytes or macrophages at the concentrations tested. Having previously shown that the cell surface binding of sulfated dextrins is dependent on the position of the negatively charged sulfate groups, we now show that their anti-HIV-1 activity in primary lymphocytes and macrophages is also dependent on the same arrangement. A phase I/II clinical trial of dextrin 2-sulfate is now in progress.

Anti-HIV Agents↗
PubMed1997

Assessing human risk to heterocyclic amines.

Heterocyclic amines such as MeIQx and PhIP are potent genotoxic chemicals which are formed at part per billion levels when meat is cooked. Using assays based on gas chromatography/mass spectrometry with stable isotope labelled analogues as internal standards we have demonstrated MeIQx and PhIP, are efficiently absorbed into the systemic circulation after ingestion of fried beef. Using a potent and selective inhibitor of human CYP1A2, furafylline, we have shown that N-hydroxylation catalysed by this enzyme is the major pathway of metabolism of MeIQx and PhIP and is solely responsible for their oxidation to mutagenic species. This is in contrast to the situation in laboratory animals in which both activation by N-hydroxylation and deactivation by C-oxidation occurs. When furafylline was administered to human volunteers before ingestion of fried beef, we showed that > 90% of MeIQx and approximately 70% of PhIP elimination could be inhibited, demonstrating the extent to which activation occurred in man. MeIQx is a very powerful mutagen in bacterial assays whereas PhIP is a more potent mammalian cell mutagen. Using a mammalian cell target gene, hprt, we have shown that PhIP induces a characteristic mutational 'fingerprint' which is identical to that detected in the Apc gene of 5/8 colonic tumours induced by PhIP in rats. These studies support a biological association between HA exposure and diet-related tumours but emphasise that information obtained from animal studies does not always reflect the situation in humans.

Animals↗
PubMed1996

Chemical methods for assessing systemic exposure to dietary heterocyclic amines in man.

A significant proportion of the mutagenic material present in cooked beef is accounted for by 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) which are formed during the cooking of meat. N-hydroxylation catalyzed by CYP1A2 is the major pathway of metbolism of MeIQx and PhIP and is solely responsible for the generation of mutagenic species. Assays for MeIQx and PhIP in foods and body fluids were developed utilising gas chromatography/mass spectrometry with stable isotope labelled analogues as internal standards. Studies using these assays have demonstrated that both MeIQx and PhIP are well absorbed and extensively metabolised following ingestion of amine-containing beef by humans. Studies in which furafylline, a potent and selective inhibitor of human CYP1A2, was administered before ingestion of beef revealed that more than 90% of MeIQx and 70% of PhIP are N-hydroxylated in vivo, probably pre-systemically in the liver. The results demonstrate that unchanged MeIQx and PhIP in urine are accurate and sensitive measures of systemic exposure to the amines.

Carcinogens↗
PubMed1996

Enzymic and interindividual differences in the human metabolism of heterocyclic amines.

Heterocyclic amines (HAs) present in cooked meat (PhIP and MeIQx) are activated only by CYP1A2 in the liver of most species, including man. This enzyme exhibits marked interindividual differences in its expression, due to induction and possibly also genetically. The absence of CYP1A2 appears to protect from HA-(PhIP and MeIQx) induced cancer, as exemplified by results in the cynomolgus monkey. Differences in the potency of these HAs are not due to differences in the kinetics of their activation. The catalytic efficiency of CYP1A2 towards HAs and their oxidative fate varies amongst species, in both cases increasing the susceptibility of humans compared to that of the rat. Interindividual and inter-organ differences in the further metabolism of N-hydroxy-HAs appear to be important determinants of cancer susceptibility, as does the glutathione S-transferase catalysed detoxication of esters of N-hydroxy-PhIP. There is a need for an effective means of quantifying the in vivo activation of HAs in man to enable the possible risk posed by these compounds to be assessed effectively.

Animals↗
PubMed1996

Heterocyclic amines: evaluation of their role in diet associated human cancer.

1. Heterocyclic amines are formed in parts per billion levels when meat is cooked. 2. The heterocyclic amines MeIQx and PhIP are efficiently absorbed into the systemic circulation after ingestion of cooked food. 3. We have shown that MeIQx and PhIP, both in vitro and in vivo, are substrates for human hepatic CYP1A2, which exclusively and efficiently catalyses their conversion to genotoxic hydroxylamines. 4. MeIQx and PhIP are promutagens. MeIQx is a very powerful bacterial mutagen whereas PhIP is a more potent mammalian cell mutagen. Using a mammalian cell target gene, hprt, we have shown that PhIP induces a characteristic mutational 'fingerprint'. 5. MeIQx and PhIP are carcinogenic in bioassays. The PhIP mutational 'fingerprint' has been detected in the Apc gene of 5/8 colonic tumours induced by PhIP in rats.

Animals↗
PubMed1996

Developmental changes in hepatic activation of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in rabbit.

MeIQx, a potent bacterial mutagen formed when meat is cooked, requires metabolic activation to exert its genotoxicity, a reaction catalysed primarily by CYP1A2 in adult mammals. Little is known about mammalian developmental changes in the mutagneic activation of compounds such as MeIQx. In rabbits we have shown previously that expression of CYP1A2 increases with age and is inducible by 3-methylcholanthrene (MC) from as early as 4 days pre-parturition. We have therefore investigated the effect of age on rabbit liver activation of MeIQx (assessed in an Ames test using Salmonella typhimurium TA98) before and after treatment of the animals with MC. MeIQx activation could not be detected using hepatic microsomal fractions from rabbits of <17 days of age. Thereafter activation increased with age to peak in weanling animals. Following MC treatment MeIQx activation was increased, being detectable in samples from rabbits as young as 9-11 days. The inducibility of MeIQx activation increased with age, reaching a plateau between 17 and 35 days. These rates of activation were broadly parallel to the changes in CYP1A2 specific content. These results indicate that the ability of rabbit liver to activate MeIQx is dependent on CYP1A2 activity, the expression of which is developmentally regulated. Although it has been established that human activation of MeIQx is also CYP1A2 dependent, whether a similar situation exists in infant humans has yet to be determined, although there is evidence that CYP1A2-dependent activity reaches a peak in late childhood.

Age Factors↗
PubMed1996

Mutational spectra of the dietary carcinogen 2-amino-1-methyl-6- phenylimidazo[4,5-b]pyridine(PhIP) at the Chinese hamsters hprt locus.

The mutagenic 'fingerprint' of the cooked food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was determined in a Chinese hamster cell line genetically engineered to express human CYP1A2 (XEMh1A2-MZ). The parental Chinese hamster V79 and XEMh1A2-MZ cells were exposed to PhIP at various concentrations for 24h. There was a dose-dependent increase in frequency of mutations at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus only in the metabolically competent XEMh1A2-MZ cells. The mutant frequency ranged from 25 to 90 X 10(-6) with final concentrations of 2.5 to 100 microM PhIP compared to 8 X 10(-6) in the solvent controls and the V79MZ cells. The molecular nature of the PhIP-induced mutations in XEMh1A2-MZ cells was determined by examining DNA sequence modifications at the hprt locus in forty five 6-thioguanine resistant (6-TGr) mutant clones. Single base substitutions predominantly GC-->TA transversions, were the major class of PhIP-induced mutation. However, a -1 frameshift 'hotspot' in a 5'-GGGA sequence was also observed. With the exception of a compound modification, all of the PhIP-induced mutations involved G.C base pairs. This is consistent with the previously observed PhIP-induced mutations in cultured mammalian cells and 32P-postlabelling experiments that show PhIP adducts to the guanine base and that major adduct is at the C8 position. Furthermore, nearly all of these mutations involved guanine bases on the non-transcribed strand which is possibly indicative of preferential repair of PhIP adducts from the transcribed strand. Nearest neighbor analysis of induced base substitutions indicates a preference for 5' guanine and 3' adenine. These data effectively define a mutation 'fingerprint' for PhIP, which may provide the basis for definitive studies on the role of PhIP in diet associated cancers such as tumours of colon. It is, therefore, intriguing that in their recent report of mutation in tumours of the colon induced by PhIP in male rate Kakiuchi et al. (Proc. Natl Acad. Sci. USA, 92, 910-914) report that four out of eight tumors had identical mutation of the tumour suppressor gene apc which is comprised of a -1 G frameshift in a 5'-GGGA sequence.

Animals↗
PubMed1996

Organ distinctive mutagenicity in MutaMouse after short-term exposure to PhIP.

We have investigated PhIP-induced mutagenicity in various tissues (kidney, liver, large and small intestine) using a transgenic mouse model (MutaMouse). In addition to tissue specific mutagenesis, we measured the binding of [14C]PhIP to MutaMouse mice blood proteins (haemoglobin and albumin), to obtain a quantitative estimate of carcinogen exposure and activation and their relationship to mutagenesis. Short-term (4 days) treatment of MutaMouse mice with [14C]PhIP by oral gavage resulted in the dose-dependent accumulation of radiolabelled material bound to haemoglobin and serum albumin. PhIP, at the highest dose (20 mg/kg), caused a 5.9-fold increase in the mutation frequency in the large intestine, a 4.2-fold increase in the mutation frequency in the small intestine but only a marginal 1.6-fold increase in the liver. However, there was no significant increase in mutations in the kidney at this dose. In contrast, there were no significant differences in any of these tissues between the vehicle control and the two lower doses (2.0 and 0.2 mg/kg respectively). These results are discussed in relationship to those previously reported for PhIP at the Dlb-1 locus.

Administration, Oral↗