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H Autrup

Publications and source records attributed to H Autrup.

At least 91 records · Page 5Linked to original sources
PubMed1982

Comparison of benzo(a)pyrene metabolism in bronchus, esophagus, colon, and duodenum from the same individual.

The metabolism of benzo(a)pyrene has been investigated in cultured normal human bronchus, colon, duodenum, and esophagus obtained from the same patient. The highest total metabolism was found in bronchus and duodenum, while the highest mean binding level was observed in the bronchus followed, in order, by the esophagus, duodenum, and transverse colon. A 30-fold interindividual variation in the binding level was found in each of the four organs studied, and a positive correlation between the binding levels in bronchus, colon, and duodenum was found. In human bronchus, a positive correlation was found between level of binding of benzo(a)pyrene to DNA and the amount of both benzo(a)pyrene 7,8-diol and the combined group of 3-hydroxybenzo(a)pyrene, benzo(a)pyrene 9,10-diol, and water-soluble metabolites. A significantly higher relative amount of benzo(a)pyrene tetrols and benzo(a)pyrene 9,10-diol was formed by human bronchus compared to the gastrointestinal tissues, while a higher level of benzo(a)pyrene phenols was formed by the latter. The relative distribution of benzo(a)pyrene-DNA adducts was similar in all four organs, the major DNA adduct being formed by trans-addition of anti-7,8-dihydroxy-9,10-epoxide-7,8,9,10-tetrahydrobenzo(a)pyrene to the 2-amino group at guanine. These results indicate that the metabolism of benzo(a)pyrene by at least four different organs is qualitatively similar but that quantitative differences exist.

Adolescent↗
PubMed1982

Metabolism of N-nitrosamines by cultured human and rat esophagus.

The metabolism of several N-nitrosamines (N-nitrosodimethylamine, N-nitrosoethylmethylamine, N-nitrosodiethylamine, N-nitrosobenzylmethylamine, and N-nitrosopyrrolidine) in cultured human and rat esophagus has been investigated by measuring (a) CO2, (b) metabolites with an oxo group, and (c) metabolites bound to DNA. Both acyclic and cyclic N-nitrosamines were metabolized by rat esophagus. The highest level of metabolite binding was seen with N-nitrosobenzylmethylamine, an organotrophic carcinogen for the rat esophagus. The binding level was about 100-fold higher than in human esophagus. This compound methylated rat esophageal DNA at positions 7 and O6 of guanine. The level of benzylation in rat was one-tenth of the level of methylation. Formation of benzaldehyde exceeded that of formaldehyde plus CO2 by a factor of six, indicating that the methylene group was preferentially oxidized. N-Nitrosoethylmethylamine, another unsymmetrical N-nitrosamine, was preferentially oxidized by rat esophagus in the ethyl group, as shown by higher formation of CO2 and acetaldehyde from the compound labeled in the ethyl group. The highest binding level to DNA from this compound was observed with the methyl group. No binding was detected to human esophagus. N-Nitrosopyrrolidine was oxidized by both rat and human esophagus in the alpha position, as measured by the formation of 2,4-dinitrophenylhydrazone derivative of 4-hydroxybutanal. Binding of metabolites of N-nitrosopyrrolidine to DNA was detected only in rat esophagus. As measured by the formation of both CO2 and formaldehyde, N-nitrosodimethylamine was metabolized by both human and rat esophagus. While most of the radioactivity associated with DNA was found to be incorporated into guanine and adenine, methylation of the guanine positions 7 and O6 was detected by chromatography of the hydrolyzed rat DNA. The results indicate significant quantitative and perhaps qualitative differences between cultured rat and human esophagus in their ability to activate N-nitrosamines, although unknown physiological differences after culture may contribute to this difference.

Alkylation↗
PubMed1982

Detection of metabolites of N-nitrosopyrrolidine and N-nitrosoethylmethylamine in cultures of human bladder epithelial cells of normal origin.

Cultured human bladder epithelial cells of normal origin are capable of metabolizing N-nitrosamines. Cultures from three different cell lines were incubated with NPYR and NEMA in order to investigate the formation of volatile N-nitrosamines. Seven volatile compounds with positive TEA response, including NDMA and NEMA, were detected in the culture media incubated with NPYR. The identity of NEMA, which was the main component of this group of metabolites, was confirmed by mass spectrometry. Culture media incubated with NEMA showed formation of NDMA. In four of five incubation experiments with NPYR, NHPYR was detected as a metabolite. The formation of metabolites containing the N-nitroso group presumably occurs via a beta-hydroxylation pathway.

Cells, Cultured↗
PubMed1982

Studies of host factors in carcinogenesis using cultured human tissues and cells.

Recent progress in the development of conditions for culturing epithelial tissues and cells from adult humans has provided cancer researchers with an opportunity to investigate directly the various facets of carcinogenesis in human cells. Studies of activation and deactivation of several classes of chemical carcinogens have revealed that the metabolic pathways and the predominant adducts formed with DNA are generally similar in humans and experimental animals. Wide quantitative interindividual differences are found in humans and other outbred animal species. When the metabolic capabilities of specimens from different levels of biological organization are compared, the profile of benzo[a]pyrene metabolites is similar in cultured tissues and cells, but subcellular fractions, e.g., microsomes, produce a qualitatively and quantitatively aberrant pattern. To test the interactive effects of cell types in the metabolic activation of carcinogens and to assess further interindividual differences among people, human tissue- and cell-mediated mutagenesis assays have been developed. The fact that terminally differentiated cells such as pulmonary alveolar macrophages can activate benzo[a]pyrene and mediate an increase in frequencies of mutations and sister chromatid exchanges in cocultivated 'detector' cell populations, i.e., Chinese hamster V79 cells, suggests that non-target cells of chemical carcinogens may play an important role in the activation of environmental carcinogens. Malignant transformation of human epithelial and fibroblastic cells in vitro has been accomplished by several research groups. Asbestos, a cocarcinogenic agent in bronchogenic carcinogenesis, has been found to induce polyploid epithelial lesions with atypical cells in human bronchial explants. Carcinogenesis studies using cultured human tissues and cells are providing new insights into the mechanisms of carcinogenesis and are useful in identifying host factors that influence individual risk to environmental carcinogens.

Biotransformation↗
PubMed1981

Metabolism of chemical carcinogens by cultured human and rat bladder epithelial cells.

The metabolism of benzo[a]pyrene, aflatoxin B1, N-nitrosodimethylamine, N-nitrosoethylmethylamine, and N-nitrosopyrrolidine has been studied in cultures of normal human and rat urinary bladder epithelial cells. The cultures were incubated with radioactively labeled carcinogens for 24 h, and the metabolism was assayed by binding of reactive metabolites to DNa and by the release of metabolites into the medium. Only slight variation in binding level of benzo[a]pyrene to DNa among the three human bladder cell lines was seen, the level of binding being higher than to rat DNA. The major benzo[a]pyrene-DNA adduct (80%) in human bladder cells eluted prior to the adducts formed by reaction of 7,8-dihydroxy-9,10-epoxy - 7,8,9,10-tetrahydrobenz[a]pyrene with guanine by high pressure liquid chromatography, but has yet to be identified. The benzo[a]pyrene-DNA adducts were quickly removed and only about 10% of the radioactivity remained associated with human bladder DNA 72 h post-treatment with benzo[a]pyrene. The 7,8- and 9,10-diols of benzo[a]pyrene were the major organo-soluble metabolites formed by both rat and human bladder cells. The primary benzo[a]pyrene metabolites were conjugated to a minor extent only. The highest level of modification of DNA was seen in the case of N-nitrosodimethylamine. N-Nitrosopyrrolidine was oxidized in both the alpha-and beta-position by all three cell lines, the oxidation at the alpha-position being predominant. No binding to DNA was detectable with N-nitrosoethylmethylamine, although this compound was metabolized as measured by the formation of CO2 and aldehydes. These results add the urinary bladder to the list of human organs which have been shown to metabolize chemical carcinogens into electropositive metabolites. However, qualitative differences exist between the data from bladder cells and those from other human organs.

Aged↗
PubMed1981

Long-term survival of normal adult human tissues as xenografts in congenitally athymic nude mice.

Bronchi, pancreatic ducts, and colons from adult human were maintained as xenografts in congenitally athymic nude N:NIH(S) mice for 715, 145, and 89 days, respectively. After an ischemic crisis and revascularization of the human tissue, the epithelium regenerated to a normal differentiated morphology. The long-term survival of normal adult human epithelial tissues as xenografts provides model systems for the study of the interactions of chemical and/or physical carcinogens with human tissues.

Animals↗
PubMed1981

Clonal growth of epithelial cells from normal adult human bronchus.

Normal primary epithelial cell cultures devoid of fibroblastic cells have been developed from tissue explants of adult human bronchi. Conditions for clonal growth of secondary cultures of bronchial epithelial cells were optimized by coculturing the human cells with mitomycin C growth-arrested Swiss 3T3 mouse feeder cells, lowering the calcium concentration of medium M199, and supplementing it with hydrocortisone, insulin, cholera toxin, epidermal growth factor, and 1.25% fetal bovine serum. The epithelial cells grew for an average of 35 population doublings and had the normal human karyotype, expressed keratin and blood group antigen epithelial cell markers, metabolized benzo(a)pyrene, and were capable of differentiating into both ciliated and squamous cells. This culture system makes it potentially possible to investigate various aspects of differentiation and carcinogenesis in human bronchial epithelial cells.

Animals↗
PubMed1980

Metabolism of aflatoxin B1, benzo[a]pyrene, and 1,2-dimethylhydrazine by cultured rat and human colon.

A model system for comparing carcinogen metabolism between human and rat colon has been developed. Tissue explants maintained under chemically defined conditions were treated with radioactively labeled carcinogens. After incubation for 24 hours, the binding of radioactive carcinogen to DNA was quantitated. Further, the carcinogen-DNA adducts and carcinogen metabolites released into the culture media were identified. Both human and rat colon activate benzo[a]pyrene (BP), aflatoxin B1 (AFB), and 1,2-dimethylhydrazine (DMH) into chemical species that reacted with cellular macromolecules. When human and rat colons were compared, the metabolism of AFB and DMH was qualitatively similar - the same major carcinogen-DNA adducts and metabolic profile. However, the mean binding levels of DMH and AFB to colonic DNA were higher in rats than in humans. BP-guanine adducts were the major adducts formed by both rat and human colonic DNA. However, BP-adenine adducts were observed in rat colonic DNA but not in human colonic DNA. A positive correlation for the binding of BP and DMH to human DNA of different individuals was observed, but no correlation was found between BP and AFB. The data suggest that similar enzyme systems may be involved in the metabolism of BP and DMH, whereas different enzymes might be involved in the metabolic activation of AFB.

1,2-Dimethylhydrazine↗
PubMed1980

Metabolism of 1,2-dimethylhydrazine by cultured human colon.

The overall metabolism of 1,2-dimethylhydrazine, and organotropic colon carcinogen in rodents, has been studied using human colon explant cultures. The binding level of 1,2-dimethylhydrazine to DNA which in this study includes both reaction of metabolites with DNA and incorporation of radioactive metabolites into DNA, showed a 100-fold variation among the 120 people studied. When different anatomical colonic sites were compared, the highest mean binding levels were found in the ascending and sigmoid colon. No significant difference in the median and mean binding levels were observed in nontumorous colon obtained surgically from patients with colon cancer and colon obtained from immediate autopsy, but decreased mean binding levels were seen in tissues obtained by surgery from patients with non-cancerous colonic disorders. Several exogenous chemicals were found to modify the metabolism. When the colon explants were co-incubated with 1,2-dimethylhydrazine and these chemicals, the binding level of 1,2-dimethylhydrazine to DNA was (a) increased by either indole 3-carbinol or phenobarbital, (b) decreased with disulfiram, butylated hydroxytoluene, or taurodeoxycholic acid, and (c) unaltered by lithocholic acid.

1,2-Dimethylhydrazine↗
PubMed1979

Metabolism of aflatoxin B1 and identification of the major aflatoxin B1-DNA adducts formed in cultured human bronchus and colon.

Aflatoxin B1 and benzo(a)pyrene were activated by both cultured human bronchus and human colon as measured by binding to cellular DNA and protein. The binding of aflatoxin B1 to DNA was dose dependent, and the level of binding was higher in cultured human bronchus than it was in the colon. When compared to aflatoxin B1, the binding level of benzo(a)pyrene to both bronchial and colonic DNA was generally higher. The major adducts formed in both tissues by the interaction of aflatoxin B1 and DNA were chromatographically identical to 2,3-dihydro-2-(N7-guanyl)-3-hydroxyaflatoxin B1 (Structure 1) with the guanyl group and hydroxy group in trans-position and an adduct which has been tentatively identified by other investigators as 2,3-dihydro-2-(N5-formyl-2',5',6'-triamino-4'-oxo-N5-pyrimidyl)-3-hydroxyaflatoxin B1 (Structure 11). Seventy % of the radioactivity associated with bronchial DNA was found in these two peaks, and the ratio of radioactivity between the peaks was nearly 1. In colonic DNA, the ratio between Structures 1 and 11 was approximately 2. These observations add aflatoxin B1 to the list of chemical procarcinogens metabolized by cultured human tissues and in which the carcinogen-DNA adducts are similar to the adducts formed in animal tissue susceptible to the carcinogenic action of aflatoxin B1.

Aflatoxins↗
PubMed1978

Explant culture of rat colon: a model system for studying metabolism of chemical carcinogens.

An explant culture system has been developed for the long-term maintenance of colonic tissue from the rat. Explants of 1 cm2 in size were placed in tissue-culture dishes to which was added 2 ml of CMRL-1066 medium supplemented with glucose, hydrocortisone, beta-retinyl acetate, and either 2.5% bovine albumin or 5% fetal bovine serum. The dishes were placed in a controlled-atmosphere chamber which was gassed with 95% O2 and 5% CO2. The chamber then was placed on a rocker platform which rocked at 10 cycles per min causing the medium to flow intermittently over the epithelial surface. The explants were incubated at 30 degrees C. The viability of the tissue was measured both by incorporation of specific precursors into cellular macromolecules and by monitoring of tissue morphology with light and electron microscopy. Cultured rat colon was able to metabolize benzo[alpha]pyrene, 7,12-dimethylbenz[alpha]anthracene, aflatoxin B1, dimethylnitrosamine, 1,2-dimethylhydrazine, and methylazoxymethanol acetate into chemical species that bind to cellular DNA and protein.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1978

Long-term organ culture of adult rat colon.

Colon explants from adult rats were maintained in culture for over 3 months in our laboratories with good epithelial preservation and cellular differentiation. The light and transmission electron microscopic features of rat colon mucosa during the culture period are described. In all the explants that remained viable, there was an initial phase of degeneration of the surface and crypt cells, later these areas were repopulated in one week, showing well-formed crypts, goblet cells, and ultrastructural features such as extensive lateral interdigitations, microvilli and glycocalyx--typical of colon. The effect of in vivo carcinogen pretreatment was also studied. The explant culture from control untreated animals showed good epithelial differentiation with crypts until 6 weeks. In contrast, the explants from animals pretreated with 4 weekly doses of azoxymethane consistently showed epithelial differentiation with well-formed crypts up to 13 weeks.

Animals↗