Formation and tumorigenicity of benzo[b]fluoranthene metabolites in mouse epidermis.

The metabolism in mouse epidermis of benzo[b]fluoranthene (BbF) was studied. [3H]BbF was applied topically, mice were killed at various intervals, and metabolites were extracted from the epidermis and analyzed by h.p.

Quantitative differences in the effects of mouse and human epidermal growth factors on A431 human tumor cells.

Human and mouse epidermal growth factor (hEGF; mEGF) bind to the same two classes of receptor sites on cell membranes prepared from the human epidermoid carcinoma cell line A431. However, the affinities of mEGF for the low affinity receptors (K(d) 3.5 X 10-9 M) and high affinity receptors (K(d) 2.

Dose-related inhibition of colon carcinogenesis by dietary piroxicam, a nonsteroidal antiinflammatory drug, during different stages of rat colon tumor development.

The effect of four dose levels of piroxicam administered during different stages of colon tumor development was studied in male F344 rats to obtain a data base on the efficacy of piroxicam as an inhibitor of colon carcinogenesis. Piroxicam was added at levels of 25, 50, 75, and 150 ppm to the NIH-07 open-formula diet and fed to male F344 rats starting 1, 13, and 23 wk after the carcinogen administration. At 7 wk of age, while the animals were consuming the control diet, all animals except the vehicle-treated controls were given s.

Enhancing effect of a bay region methyl group on tumorigenicity in newborn mice and mouse skin of enantiomeric bay region diol epoxides formed stereoselectively from methylchrysenes in mouse epidermis.

The stereochemistry of diol epoxide formation in mouse epidermis upon topical application of [3H]-1R,2R-dihydroxy-1,2-dihydro-5-methylchrysene ([3H]-5-MeC-1R,2R-diol) and [3H]-6-MeC-1R,2R-diol, and the tumorigenicity in mouse skin and in newborn mice of the R,S,S,R and S,R,R,S enantiomers of 1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (5-MeC-1,2-diol-3,4-epoxide), 5-MeC-7,8-diol-9,10-epoxide, and 6-MeC-1,2-diol-3,4-epoxide were examined. Analysis of tetraols and their derived tetraacetates present in mouse epidermis, 2 h after application of [3H]-5-MeC-1R,2R-diol or [3H]-6-MeC-1R,2R-diol, demonstrated greater than 90% stereoselectivity in formation of 5-MeC-1R,2S-diol-3S,4R-epoxide and 6-MeC-1R,2S-diol-3S,4R-epoxide. Taken together with previous data, these results demonstrate that there is a high degree of stereoselectivity for formation of R,S,S,R enantiomers of 5-MeC- and 6-MeC-1,2-diol-3,4-epoxides in mouse skin.

Contrasting disposition and metabolism of topically applied benzo(a)pyrene, trans-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene, and 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene in mouse epidermis in vivo.

Whereas extensive evidence indicates that 7 beta,8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (anti-BPDE) is a major ultimate carcinogen of benzo(a)pyrene (BaP) in mouse skin, tumorigenicity studies have consistently shown that anti-BPDE is less active then BaP in this model system. In order to investigate factors responsible for this apparent contradiction, we have compared the disposition, metabolism, and DNA binding of [3H]BaP, (+/-)-trans-7,8-[14C]dihydroxy-7,8-dihydrobenzo(a)pyrene [(+/-)-[14C]BaP-7,8-diol), and (+/-)-anti-[3H]BPDE in mouse epidermis in vivo. There were remarkable differences in the total radioactivity recovered in epidermis at various times after topical application of BaP, BaP-7,8-diol, and anti-BPDE.

Tobacco-specific nitrosamines in the saliva of Inuit snuff dippers in the Northwest Territories of Canada.

Levels of tobacco-specific nitrosamines (TSNA), nicotine and cotinine were estimated in the saliva of 20 snuff dippers (Inuit, Northwest Territories, Canada). Levels of N'-nitrosonornicotine (NNN), 4-(methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and N-nitrosoanatabine (NAT) plus N-nitrosoanabiasine (NAB) found in the saliva following a 15-min period of keeping 0.5-1.

Effect of snuff and nicotine on DNA methylation by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

In this study we assayed the effects of snuff and nicotine on the DNA methylation by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a powerful tobacco-specific N-nitrosamine. Male F344 rats were pretreated for 2 weeks with either a solution of a snuff extract or 0.002% nicotine in the drinking water.

The hepatocyte primary culture/DNA repair test using hepatocytes from several species.

The hepatocyte primary culture/DNA repair test, originally validated with rat hepatocytes, has been extended to use hepatocytes from other species including mouse, hamster, guinea pig, rabbit, monkey and human. Both qualitative and quantitative differences have been observed when chemicals are examined in the hepatocyte primary culture/DNA repair test using hepatocytes from more than one species. Examples are discussed that illustrate that the genotoxicity of a chemical can be a species-specific response and that multi-species testing permits a more complete assessment of genotoxicity.

The role of N-(nitrosomethylamino)propionitrile in betel-quid carcinogenesis.

N-(Nitrosomethylamino)propionitrile (NMAP) was isolated and identified in the saliva of betel-quid chewers in amounts ranging from 0.5 to 11.4 micrograms/l.

A study of snuff carcinogenesis.

Dry snuff contains high levels of tobacco-specific N-nitrosamines (TSNA); their concentrations exceed by more than 100 times the quantities of nitrosamines found in any other consumer product. The concentrations of TSNA are similar in dry snuff and in the more popular moist snuff. In addition to the four TSNA identified earlier [N'-nitrosonornicotine (NNN), 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK), N'-nitrosoanatabine (NAT) and N'-nitrosoanabasine (NAB)], two new nitrosamines were detected in snuff, namely 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanol (NNAl; 0.

Investigations on the molecular dosimetry of tobacco-specific N-nitrosamines.

Approaches for assessing molecular dosimetry of 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) in humans by measurement of haemoglobin or DNA adducts are discussed. NNK and NNN form haemoglobin adducts in Fischer 344 rats. Acid or base hydrolysis of the globin gives 4-hydroxy-1-(3-pyridyl)-1-butanone, which can be detected in rat blood up to six weeks after injection of NNK; it may be a useful marker for assessing uptake and metabolic activation of NNK and NNN in tobacco consumers.

Identification of metabolites of benzo[j]fluoranthene formed in vitro in rat liver homogenate.

The metabolites of benzo[j]fluoranthene (BjF) as formed in vitro using the 9000 X g supernatant from Aroclor-pretreated rats have been identified. Two dihydrodiols, trans-4,5-dihydro-4,5-dihydroxyBjF and trans-9,10-dihydro-9,10-dihydroxyBjF have been identified as major metabolites by comparison of their spectral and chromatographic properties with those of pure synthetic standards. There was no evidence that any of the isomeric 2,3-dihydrodiol was formed as a metabolite of BjF under these incubation conditions.

Amino acid transport in established adult rat liver epithelial cell lines.

The capacities of Na+-dependent transport of alpha-aminoisobutyrate, glutamine and glutamate in four established and three transformed rat liver epithelial cell lines were found to be considerably higher than those of isolated and cultured hepatocytes. At least for transport systems A and G- this seemed to be due to elevated values of Vmax, whereas the values for Km were quite comparable to those of hepatocytes. In contrast to hepatocytes, however, no significant hormonal stimulation of amino acid uptake could be detected in the cell lines.

Activities of chlorinated ethane and ethylene compounds in the Salmonella/rat microsome mutagenesis and rat hepatocyte/DNA repair assays under vapor phase exposure conditions.

Three chlorinated ethane and ethylene solvent products were examined for their genotoxicity in the Salmonella/microsome mutagenesis and hepatocyte primary culture DNA repair assays using vapor phase exposures. The positive control in this study, monochloroethylene (vinyl chloride), induced reversion mutation of Salmonella tester strains TA100 and TA1535 with enhancement by an exogenous activation system and elicited unscheduled DNA synthesis in rat hepatocytes in culture. Exposures to 1,1,1-trichloroethane (methyl chloroform) or 1,1,2-trichloroethylene samples which contained stabilizers resulted in increased recovery of revertant colonies of Salmonella at concentrations causing greater than 96% cell killing.

A comparison of different nutrient media and supplementation with dexamethasone for mouse colon organ culture.

Several complex nutrient media were compared for their effectiveness in maintaining viable and functional mouse colon mucosa in organ culture. The order of superiority for preserving survival of normal tissues for 14 days was: Williams' Medium E greater than Morgan's 199 greater than CMRL-1066 greater than Waymouth's MB 752/l greater than Eagle's MEM greater than Trowell's T8. The 3H-thymidine labeling index was highest in colon explants maintained in Morgan's 199 greater than Williams' Medium E greater than Waymouth's MB 752/l greater than CMRL-1066 greater than Eagle's MEM.

Abnormalities in liver iron accumulation during N-2-fluorenylacetamide hepatocarcinogenesis that are dependent or independent of continued carcinogen action.

The characteristics of liver iron accumulation were studied during N-2-fluorenylacetamide (FAA)-induced hepatocarcinogenesis in rats. After injection of iron-dextran in control rats, hepatocytes accumulated stainable iron evenly throughout hepatic lobules. During the feeding of FAA, iron accumulation was reduced in the midzonal and centrilobular regions.

DNA content of hyperplastic and neoplastic acinar cell lesions in rat and human pancreas.

Pancreatic acinar cell hyperplastic lesions and neoplasms in rats and humans were studied for their nuclear DNA content by microspectrophotometry. Atypical hyperplastic acinar cell lesions induced in rats by azaserine displayed a wide range of DNA contents, 1.5-8C for those composed of acidophilic-type cells and 1.

Phenotypic Properties of Preneoplastic Rat Liver Lesions and Applications to Detection of Carcinogens and Tumor Promoters.

A variety of cellular lesions arise during liver carcinogenesis by chemicals in rats. The altered focus is a lesion of hepatocytes that occurs early in hepatocarcinogenesis and appears to give rise to both neoplastic nodules and carcinomas. Foci display numerous phenotypic abnormalities which together with nuclear abnormalities indicate that they are truly a new altered population.

Differential effects of ethanol and other inducers of drug metabolism on the two forms of hamster liver microsomal aniline hydroxylase.

The aniline hydroxylase activity of microsomes isolated from hamster liver can be differentiated kinetically into high affinity (low K(m), form I) and low affinity (high K(m), form II) forms. Microsomes isolated from uninduced animals contain slightly more form I activity. The activity of the low affinity form (form II) is preferentially enhanced by Aroclor or 3-methylcholanthrene treatment, while phenobarbital treatment increases the activity of both forms.

The formation of azoxymethane, a colon carcinogen, during the chemical oxidation of methylamine.

Simple chemical oxidation of methylamine in aqueous solution or in methanol leads to the formation of significant amounts of azoxymethane, a strong carcinogen in rodents. Methods, including high pressure liquid chromatography, differential pulse polarography and gas chromatography-mass spectrometry, used for the identification of the carcinogen, are described.

Alteration by phenobarbital of membrane-associated enzymes including gamma glutamyl transpeptidase in mouse liver neoplasms.

Administration of phenobarbital for 5 to 7.5 weeks to aged C3HfB/HeN mice with spontaneous liver tumors produced an enhancement of gamma glutamyl transpeptidase activity in the tumors and a decrease in glucose-6-phosphatase and adenosine triphosphatase activity. Discontinuation of phenobarbital feeding for 5.

The deficiency of cyclic AMP responsive G1 controls in cultured malignant liver epithelial cells.

Normal rat liver epithelial cells in culture were blocked outside the S phase by dibutyryl cyclic AMP while malignant rat liver epithelial cells were slowed in S phase. It is suggested that this lack of normal response to a growth inhibitory factor by malignant cells may underly their relatively autonomous growth behavior.