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Biomedical subjects

G N Wogan

Publications and source records attributed to G N Wogan.

At least 19 recordsLinked to original sources
PubMed1995

Nitric oxide production in relation to spontaneous B-cell lymphoma and myositis in SJL mice.

SJL mice spontaneously develop B cell lymphomas (historically described as reticulum cell sarcomas) by 12 months of age and inflammatory muscle disease (myositis) by 6 months of age. Tumors originate in mesenteric lymph nodes and in Peyer's patches and resemble human germinal center lymphomas. The growth of reticulum cell sarcomas is completely dependent on cytokine production by normal T cells. The spontaneous myositis, which resembles human idiopathic myositis, is characterized by various abnormalities in skeletal muscle, including infiltration with inflammatory cells consisting primarily of macrophages. The participation of different cytokines in the pathogenesis of the lymphoma and the massive invasion of macrophages into muscle tissues led us to investigate the possible involvement of nitric oxide (NO.), which is known to be synthesized by activated macrophages under inflammatory conditions. Elevated NO. production, measured by urinary nitrate excretion, by SJL mice in comparison with BALB/c control mice was observed as early as 7 weeks of age. Both aging and degree of spontaneous myositis correlated with increased nitric oxide production. Oral administration of N-monomethyl-L-arginine, an inhibitor of nitric oxide synthase (NOS), reduced urinary nitrate excretion and also the severity of myositis. Immunohistochemical analysis revealed the presence of inducible NOS (iNOS) in cells in the spleen, lymph nodes, and skeletal muscle. The iNOS is primarily responsible for the enhanced nitric oxide production. Morphology of cells that stained positive for iNOS was similar to that of macrophages infiltrating into the affected tissues. Chronic production of elevated amounts of nitric oxide by the SJL mice, therefore, provides a useful in vivo model for future studies of cellular damage resulting from endogenously produced NO.in combination with oxygen radicals.

Amino Acid Oxidoreductases↗
PubMed1995

Tissue distribution of DNA adducts in pre-weanling BLU:Ha mice treated with a tumorigenic dose of fluoranthene.

Fluoranthene (FA), a ubiquitous atmospheric pollutant, is tumorigenic to the lung when injected into BLU:Ha mice 1, 8, and 15 days after birth. DNA adducts were measured by a modified HPLC-32P-postlabeling method in target (lung) and non-target (liver, kidney, spleen plus thymus) organs of 16-day-old mice 24 h after the last treatment with a tumorigenic dose (3.5 mg/mouse) of FA. The anti-FADE adduct was the major DNA adduct and was present at levels ranging from 3.5 to 37 adducts per 10(8) nucleotides (106-1138 fmols/mg DNA) in all DNA samples from the organs of FA-treated mice. The lung contained anti-FADE adduct levels approximately 2, 2.5 and 5 times higher than those in kidney, liver, and spleen plus thymus, respectively. There was no significant difference between anti-FADE adduct levels in liver and kidney; however, adduct levels were significantly higher than those in spleen plus thymus. Significant variation was found among litters in anti-FADE adduct levels from lung, liver, and kidney, but not from spleen plus thymus. An unidentified peak was present in the adduct profile of the kidneys of treated but not control animals. Three additional unidentified radioactive peaks were present in adduct profiles of DNA from tissues of both treated and control animals, but their levels were significantly higher in the tissues of treated animals than in controls. Possible correlations between tumorigenic response and DNA adduct formation are discussed.

Animals↗
PubMed1995

Formation and persistence of DNA adducts in organs of CD-1 mice treated with a tumorigenic dose of fluoranthene.

Fluoranthene (FA) is tumorigenic to the lung when injected i.p. into CD-1 mice 1, 8 and 15 days after birth (Wang, J.-S. and Busby, W.F. Jr, Carcinogenesis, 14, 1871-1874, 1993). Levels, tissue distribution and persistence of FA--DNA adducts detected by HPLC-32P-postlabeling were investigated during the course of lung tumorigenesis by FA. Anti-10b-N2-deoxyguanosin-1,2,3,-trihydroxy-1,2,3 10b-tetrahydrofluoranthene [sequence: see text] (anti-FADE adduct) was consistently the major adduct in DNA samples from lung, heart, liver and kidney of animals examined at different time points from 2 h to 165 days after the last treatment with the tumorigenic dose (3.5 mg/mouse) of FA. Several unidentified adducts were also detected. Lung, the target organ for FA tumorigenicity, contained higher levels of anti-FADE adduct than other tissues from 1-165 days after treatment. The anti-FADE adduct level decreased in a biphasic manner after reaching maximum values at 2 h in heart and spleen plus thymus and 3 days in lungs, liver and kidneys. About 10% of the maximum amount of anti-FADE adduct remained in lung, liver and heart 165 days after final FA treatment, at which time 44% of animals had developed lung adenomas. Significant inter-litter variations, but no sex differences in adduct levels were observed. These results indicated a positive correlation between anti-FADE adduct level and persistence in relation to target organ specificity for tumor formation.

Animals↗
PubMed1992

Urinary aflatoxin biomarkers and risk of hepatocellular carcinoma.

Aflatoxins have long been suspected to be human hepatic carcinogens but no direct study was feasible until assays to measure individual aflatoxin exposure became available. We have used assays for urinary aflatoxin B1, its metabolites AFP1 and AFM1, and DNA-adducts (AFB1-N7-Gua) to assess the relation between aflatoxin exposure and liver cancer, as part of an ongoing prospective study of 18,244 middle-aged men in Shanghai, People's Republic of China. After 35,299 person-years of follow-up, 22 cases of liver cancer had been identified. For each case, 5 or 10 controls were randomly selected from cohort members without liver cancer on the date the disorder was diagnosed in the case and matched to within 1 year for age, within 1 month for sample collection, and for neighbourhood of residence. Subjects with liver cancer were more likely than were controls to have detectable concentrations of any of the aflatoxin metabolites (relative risk 2.4, 95% confidence interval 1.0-5.9). The highest relative risk was for aflatoxin P1 (6.2, 1.8-21.5). In an analysis adjusting for the effects of hepatitis B surface antigen seropositivity, level of education, cigarette smoking, and alcohol consumption, the relative risk for the presence of aflatoxin metabolites was 3.8 (1.2-12.2). There was a strong interaction between serological markers of chronic hepatitis B infection and aflatoxin exposure in liver-cancer risk. Reduction of aflatoxin exposure may be a useful intermediate goal in prevention of liver cancer, since the benefits of wide-scale hepatitis B vaccination will not be apparent for many years.

Aflatoxins↗
PubMed1992

Aflatoxins as risk factors for hepatocellular carcinoma in humans.

On a global basis, primary liver cancer (PLC) is a very prevalent form of cancer. Wide variation of PLC incidence in different areas of the world suggests the involvement of environmental factors in its etiology. Two major classes of risk factors have been identified. Extensive evidence indicates the importance of infection by the hepatitis B virus as a major risk factor for PLC. Because many organic chemicals induce liver cancer in experimental animals, those to which human exposure is known to occur are also of interest with respect to their possible involvement as risk factors for PLC. Particular emphasis has been placed on aflatoxins because of the frequency with which they occur as food contaminants, together with their potency as liver carcinogens for a large number of experimental animals, including subhuman primates. Other mycotoxins, notably sterigmatocystin and fumonisin, also are relatively potent carcinogens for the liver of animals, but little is known about human exposure to them. Epidemiological surveys carried out over the past 25 years in Asia and Africa have revealed a strong statistical association between aflatoxin ingestion and PLC incidence. The combined experimental and epidemiological evidence has led to designation of aflatoxins as human carcinogens according to International Agency for Cancer Research criteria. Collectively, current evidence strongly suggests that PLC is of multifactorial origin, with probable interactions between viral and chemical agents in populations concurrently exposed to both classes of risk factors. Recently developed methods that permit individual monitoring of aflatoxin exposure, hepatitis B virus infection, and genetic damage caused by these agents are being applied in the design of molecular and biochemical epidemiological studies of the etiology of the disease. Application of this methodology may contribute to elucidation of the relative importance of interacting etiological agents in different populations.

Aflatoxin B1↗
PubMed1992

Molecular dosimetry in rat urine of aflatoxin-N7-guanine and other aflatoxin metabolites by multiple monoclonal antibody affinity chromatography and immunoaffinity/high performance liquid chromatography.

The development of molecular dosimetry methods will simplify the identification of people at high risk for cancer. A combined monoclonal antibody immunoaffinity chromatography/high performance liquid chromatography method has been devised to isolate and quantify aflatoxin-DNA adducts and other metabolites in rat urine samples. We report the production of 11 different monoclonal antibodies recognizing aflatoxin B1, aflatoxin Q1, aflatoxin G1, aflatoxicol, and aflatoxin M1 and the application of these antibodies to a multiple monoclonal antibody affinity chromatography technique. Using the multiple monoclonal antibody affinity column with rat urines obtained from dosed animals, between 90 and 95% of total aflatoxin metabolites can be bound to the column and isolated. Analytical immunoaffinity chromatography/high performance liquid chromatography analysis of these isolated aflatoxins reveals that more than 55% of the aflatoxins in rat urine are aflatoxin-dihydrodiol, aflatoxin-N7-guanine, aflatoxin Q1, aflatoxin M1, aflatoxin P1, and aflatoxin B1, accounting for 1.5, 9.6, 1.8, 34.5, 8.0, and 1.0% of the total aflatoxins, respectively. Further, a perchloric acid digestion of the aflatoxin-N7-guanine peak was used to confirm its identity by its conversion to guanine. The measurement of aflatoxin-N7-guanine excretion in rat urine was examined to assess its utility as a marker of DNA adduct formation in the liver, and a dose-dependent excretion in urine was found with a correlation coefficient of 0.99. A comparison of the dose-dependent residual levels of aflatoxin binding to liver DNA with the amount of aflatoxin-N7-guanine excreted in urine showed a correlation coefficient of 0.98. Besides the nucleic acid adduct excretion data, aflatoxin M1 and aflatoxin P1 were evaluated as molecular dosimeters in the urine. Aflatoxin M1 was found to be an excellent marker, whereas no linear relationship between dose and aflatoxin P1 excretion in urine was found.

Aflatoxin B1↗
PubMed1992

Molecular dosimetry of urinary aflatoxin-DNA adducts in people living in Guangxi Autonomous Region, People's Republic of China.

Hepatocellular carcinoma is one of the five leading human cancers causing at least 250,000 deaths each year. One of the major risk factors for this disease is exposure to dietary aflatoxins, and the development of appropriate molecular dosimetry biomarkers would facilitate the identification of individuals at risk. This study was undertaken to explore the relationship between dietary intake of aflatoxins and the excretion of the major aflatoxin-DNA adduct and other metabolites into the urine of chronically exposed people. The following protocol was developed for this investigation in Guangxi Autonomous Region, People's Republic of China, where the diets of 30 males and 12 females (ages, 25-64 years) were monitored for 1 week and aflatoxin intake levels determined each day. Starting on the fourth day, total urine volumes were obtained in consecutive 12-h fractions for 3 or 4 days. High performance liquid chromatography and competitive radioimmunoassay analyses were done on each of the urine samples, and the relationships between excretion of total aflatoxin metabolites, aflatoxin-N7-guanine, aflatoxin M1, aflatoxin P1, and aflatoxin B1, and aflatoxin B1 intake values were determined. The average intake of aflatoxin B1 by men was 48.4 micrograms/day, giving a total mean exposure during the study period of 276.8 micrograms. The average daily intake by women was 77.4 micrograms/day, resulting in a total average exposure during the 7-day period of 542.6 micrograms aflatoxin B1. Initial efforts to characterize aflatoxin metabolites in urine samples were with an analysis by competitive radioimmunoassay. The analysis by linear regression of the association between aflatoxin B1 intake/day and total aflatoxin metabolite excretion/day showed a correlation coefficient of only 0.26. These findings stimulated the immunoaffinity/analytical high performance liquid chromatography analysis for individual metabolites. When the data were analyzed by linear regression analysis, the aflatoxin N7-guanine excretion and aflatoxin B1 intake from the previous day showed a correlation coefficient of 0.65 and P less than 0.000001. Similar analysis for aflatoxin M1 resulted in a correlation coefficient of 0.55 and P less than 0.00001, whereas there was no positive statistical association between exposure in the diet and aflatoxin P1 excretion, despite aflatoxin P1 being quantitatively a major metabolite. Analysis of the total aflatoxin-N7-guanine excretion in the urine during the complete collection period plotted against the total aflatoxin B1 exposure in the diet for each of the individuals, smoothing the day to day variations, revealed a correlation coefficient of 0.80 and P less than 0.0000001.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Molecular epidemiology in cancer risk assessment and prevention: recent progress and avenues for future research.

Molecular epidemiology is increasingly being applied in studies of cancer risks derived from exposure to environmental carcinogens of both endogenous and exogenous origins. Analytical methods have been developed that are capable of detecting and quantifying levels of covalent adducts of several important classes of carcinogens with cellular DNA and blood proteins. Methods of sufficient sensitivity and specificity to detect ambient levels of exposure are in current use. These are being used in studies related to tobacco use (polycyclic aromatic hydrocarbons, aromatic amines, tobacco-specific nitrosamines); dietary exposures (aflatoxins, N-nitrosamines, heterocyclic amines); medicinal exposures (cisplatin, alkylating agents, 8-methoxypsoralen, ultraviolet photoproducts); occupational exposures (aromatic amines, polycyclic aromatic hydrocarbons, oxides of ethylene and styrene, and vinyl chloride); and oxidative damage (8-hydroxyguanine, thymine glycol). Methodologic improvements together with their expanded use in feasibility studies continue to produce results that support the validity of this approach for detecting and quantifying exposure to carcinogens. Genetic markers are also being used to detect early biological responses in efforts to link carcinogen exposure to initiating events in the carcinogenesis process. These include, in addition to traditional cytogenetic markers (e.g., chromosomal aberrations, sister chromatid exchange, micronuclei), other alterations in chromosomal structure such as restriction fragment length polymorphisms, loss of heterozygosity, and translocation markers. Specific genetic changes have recently been identified as critical molecular events in the initiation and development of many cancers. Important among these are activation of oncogenes, especially those of the ras family, and inactivation of tumor-suppressor genes (e.g., p53 and Rb) by point mutations and/or chromosomal deletions and other structural changes. Although some of these changes are known to occur in chemically induced tumors of experimental animals, the possible role of chemical carcinogens in the induction of genetic abnormalities in human cancers has yet to be determined. Continuing investigations employing the methods of molecular epidemiology promise to provide further evidence concerning these relationships. Future investigations employing newly developed molecular biological methods, in particular those based on polymerase chain reaction amplification of DNA, to identify alterations in DNA and chromosomal structure, combined with methods for characterizing exposure to carcinogens and early effects, have great potential for further elucidating the role of genotoxic agents in the etiology of human cancers and also for the development of strategies for their prevention.

Biomarkers, Tumor↗
PubMed1991

The TPR-MET oncogenic rearrangement is present and expressed in human gastric carcinoma and precursor lesions.

The TPR-MET oncogenic rearrangement was originally observed in an in vitro transformed human osteosarcoma cell line. Recently, we detected the expression of this rearrangement at very low levels in several cell lines derived from human tumors of nonhematopoietic origin using a highly sensitive method based on polymerase chain reaction amplification of the transcript. We report here the results of analysis of TPR-MET expression in cell lines derived from human gastric tumors and 22 biopsy samples of human gastric mucosa showing cancer or precursor lesions. The rearranged RNA was expressed in all four cell lines as well as in biopsy samples from 12 of the 22 patients. Overexpression of TPR-MET RNA in superficial gastritis lesions with hyperplasia of glandular neck cells suggests the possible involvement of this oncogene at an early stage of gastric tumorigenesis. Analysis of gastric biopsy samples for RAS gene mutations showed base substitutions occurring in the codon 12 region of Ki- and Ha-RAS genes in four cases, including two precursor lesions.

Base Sequence↗
PubMed1990

Comparative tissue distribution and excretion of orally administered [3H]diacetoxyscirpenol (anguidine) in rats and mice.

A quantitative comparison of tissue distribution and excretion of an orally administered sublethal dose of [3H]diacetoxyscirpenol (anguidine) was made in rats and mice 90 min, 24 hr, and 7 days after treatment. Total recoveries of 95-100% were obtained. Approximately 90% of the dose was excreted in urine and feces during the first 24 hr with a feces:urine ratio of about 1:4.5 in both species. Carcass and tissue radioactivity dropped rapidly during the first 24 hr but remained relatively constant at low, but detectable, levels (1.5-3.5% of dose) over the course of the experiment. Few substantive interspecies differences were noted in tissue distribution. At 90 min the highest percentage of dose was in tissues involved in sequestering diacetoxyscirpenol because of high body water/lipid content (carcass, skin) or the absorption (stomach, small intestine), metabolism (liver), or excretion (kidney) of the toxin. The rank order of these tissues was generally stable over the course of the experiment. When data were expressed as specific radioactivity (dpm/g tissue) instead, the carcass and skin dropped from the top rank tissues at 90 min and were replaced by the spleen and cecum. At 24 hr and 7 days the top-ranked order of tissues shifted to include organs associated with trichothecene-induced toxicity such as the lymphohematopoietic system (spleen, thymus, and femur bone marrow), heart, and testis (in mouse) as well as the cecum and large intestine. In addition, the rate of loss of radioactivity with time generally did not decrease as rapidly in these target organs as observed in liver, kidney, skin, and carcass. Brain radioactivity, though very low, also diminished relatively slowly. Significant differences in specific radioactivity which did occur between the rat and mouse tended to occur in target organs and with the higher levels present in the mouse. These data were discussed in terms of interspecies differences in lethality and target organ toxicity.

Administration, Oral↗
PubMed1990

TPR-MET oncogenic rearrangement: detection by polymerase chain reaction amplification of the transcript and expression in human tumor cell lines.

Activation of the MET protooncogene by a rearrangement involving the fusion of TPR and MET specific gene sequences has been observed in a human osteosarcoma cell line (HOS) treated in vitro with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). No information has been available about the possible occurrence of this rearrangement in human tumors. To facilitate rapid screening of human cell lines and tumor samples for this specific gene rearrangement, we developed a sensitive detection method based on polymerase chain reaction (PCR) amplification of TPR-MET mRNA. cDNA was generated from cellular transcripts by using one of the PCR primers, which was then used as a template for PCR amplification of a 205-base-pair region carrying the breakpoint. An end-labeled internal probe was hybridized in solution to an aliquot of the PCR product for detecting amplification. Cells could be directly screened by the assay without prior isolation of RNA. A 205-base-pair DNA fragment characteristic of the TPR-MET rearrangement was detected in cell lines previously known to contain this altered sequence. The rearrangement was also detected at very low levels in the parental (nontransformed) cell line, HOS TE-85. A preliminary survey of cell lines derived from a variety of human tumors indicates that TPR-MET rearrangement occurred and was expressed at very low frequencies by cells from 7 of 14 tumors of nonhematopoietic origin.

Animals↗
PubMed1990

Mutations in c-Ki-ras oncogenes in diseased livers of winter flounder from Boston Harbor.

Livers of a natural population of winter flounder from a contaminated site in Boston Harbor were examined for the presence of oncogenes by transfection of DNA into NIH 3T3 mouse fibroblasts. Tissues analyzed contained histopathologic lesions including abnormal vacuolation, biliary proliferation, and, in many cases, hepatocellular and cholangiocellular carcinomas. Fibroblasts transfected with liver DNA samples from 7 of 13 diseased animals were effective in the induction of subcutaneous sarcomas in nude mice. Further analysis revealed the presence of flounder c-Ki-ras oncogenes in all 10 nude mouse subcutaneous tumors analyzed. Direct DNA sequencing and allele-specific oligonucleotide hybridization following amplification of the tumor DNA by the polymerase chain reaction showed mutations in the 12th codon in this gene. Analysis of DNA from all nude mouse tumors as well as the livers from which they were derived showed mutations at this codon. The mutations comprised G.C----A.T or G.C----T.A base changes resulting in substitution of serine, valine, or cysteine for glycine. Liver DNA samples from five histologically normal livers of animals from a less polluted site were ineffective in the transfection assay and showed only wild-type DNA sequences (GGT) at the 12th codon of c-Ki-ras. The prevalence of mutations in this gene region was associated with the presence of liver lesions and could signify DNA damage resulting from environmental chemical exposure.

Animals↗
PubMed1990

Characterization of c-Ki-ras and N-ras oncogenes in aflatoxin B1-induced rat liver tumors.

c-Ki-ras and N-ras oncogenes have been characterized in aflatoxin B1-induced hepatocellular carcinomas. Detection of different protooncogene and oncogene sequences and estimation of their frequency distribution were accomplished by polymerase chain reaction, cloning, and plaque screening methods. Two c-Ki-ras oncogene sequences were identified in DNA from liver tumors that contained nucleotide changes absent in DNA from livers of untreated control rats. Sequence changes involving G.C to T.A or G.C to A.T nucleotide substitutions in codon 12 were scored in three of eight tumor-bearing animals. Distributions of c-Ki-ras sequences in tumors and normal liver DNA indicated that the observed nucleotide changes were consistent with those expected to result from direct mutagenesis of the germ-line protooncogene by aflatoxin B1. N-ras oncogene sequences were identified in DNA from two of eight tumors. Three N-ras gene regions were identified, one of which was shown to be associated with an oncogene containing a putative activating amino acid residing at codon 13. All three N-ras sequences, including the region detected in N-ras oncogenes, were present at similar frequencies in DNA samples from control livers as well as liver tumors. The presence of a potential germ-line oncogene may be related to the sensitivity of the Fischer rat strain to liver carcinogenesis by aflatoxin B1 and other chemical carcinogens.

Aflatoxin B1↗
PubMed1990

The aflatoxin-lysine adduct quantified by high-performance liquid chromatography from human serum albumin samples.

Aflatoxin B1 (AFB1) exposure from the diet is a major risk factor for the development of liver cancer in people living in regions of China and Africa. Rapid methods to assess the exposure status of these individuals to genotoxic damage imparted by AFB1 will be very important for cancer prevention strategies. Serum albumin is a readily accessible target protein for AFB1 and we report here the development of an accurate and sensitive method to quantitate the major AFB1 serum albumin adduct, aflatoxin-lysine, from less than 100 microliters of serum by combined immunoaffinity chromatography/high-performance liquid chromatography (IAC/HPLC) with fluorescence detection. For this method, serum is digested with Pronase and the adducts are purified by monoclonal antibody IAC and quantified by HPLC. Analysis of human serum samples obtained from an exposed population revealed a highly significant correlation coefficient (up to 0.82 for male samples) between aflatoxin-lysine adduct levels and AFB1 consumption. These data suggest that aflatoxin-lysine is an excellent molecular dosimeter for exposure assessment. To determine whether the liver is the sole site of aflatoxin-albumin adduct formation, preliminary experiments with isolated perfused rat liver were done. These data showed that AFB1 metabolites covalently react not only with albumin in the hepatocyte, but also with circulating proteins in the perfusate. This suggests that a reactive aflatoxin metabolite secreted by the liver may form serum albumin adducts in circulating blood. Taken together, the analysis of aflatoxin-lysine could prove a very useful tool for epidemiological studies.

Aflatoxin B1↗
PubMed1989

Fluoranthene-DNA adducts: identification and quantification by an HPLC-32P-postlabeling method.

A 32P-postlabeling procedure for identifying and quantifying fluoranthene (FA)-DNA adducts has been developed through modifications of the method of Randerath and collaborators. In this modified procedure, labeled adducts are separated chromatographically by high-pressure liquid chromatography (HPLC) and quantified by liquid scintillation counting. FA-modified DNA is digested to nucleotide 3'-monophosphates and nucleotide 3'-monophosphate adducts; unmodified nucleotides are then separated from adducts using a disposable C18 cartridge. Residual unmodified nucleotides, which reduce the efficiency of 32P-postlabeling of FA adducts, are removed by brief digestion with nuclease P1. This treatment selectively dephosphorylates unmodified nucleotide 3'-monophosphates, while FA adducts are minimally affected. FA adducts are then 5'-phosphorylated with polynucleotide kinase and [gamma-32P]ATP. Prolonged treatment with nuclease P1 then is employed to remove the unlabeled 3'-phosphate from adducted diphosphate nucleotides, following which adducts are separated by HPLC and quantified by liquid scintillation counting. Postlabeled microsomally-activated FA-modified DNA contained adducts derived from anti- and syn-2,3-dihydroxy-1,10b-epoxy-1,2,3-trihydrofluoranthene. The identity of the major adduct in DNA-bound microsomally-activated FA was confirmed by this HPLC-32P-postlabeling method as an anti-2,3-dihydroxy-1,10b-epoxy-fluoranthene nucleotide adduct. Each step in the procedure was optimized with respect to experimental conditions, and the recovery of adducts was determined by analysis of DNA modified with [3H]FA. In repeated analyses of 2-50 micrograms DNA containing 1.8 adducts per 10(8) nucleotides, 10-15% of total DNA-bound [3H]FA was recovered as the major adduct; recovery was greater from DNA containing higher levels of adducts. The reproducibility of multiple analyses of the same sample was approximately 5%, and multiple analyses at different times were reproducible within experimental error. The limit of detection of the method was approximately 0.1 fmol adduct, representing a binding level of approximately 3 adducts per 10(8) nucleotides in 1 microgram DNA or approximately 1 adduct per 10(10) nucleotides in 500 micrograms DNA. Because the method is not limited with respect to the amount of DNA that can be subjected to analysis, the inherent sensitivity for adduct detection can be greatly enhanced by analysis of larger quantities of DNA.

Animals↗
PubMed1989

Formation of DNA and hemoglobin adducts of fluoranthene after single and multiple exposures.

The dose-dependence of hemoglobin binding as well as distribution of fluoranthene and fluoranthene-DNA adducts in various tissues was characterized in male rats 24 h after a single i.p. injection of [3H]fluoranthene. Formation and distribution of DNA adducts after chronic administration of fluoranthene in the diet was also studied. Fluoranthene-derived radioactivity was widely distributed throughout the animal after a single dose, and excreta contained the greatest amounts of radioactivity at all dose levels. Fluoranthene binding to globin was proportional to dose over the range of 2 nmol/kg to 177 mumol/kg, and the adducted protein was cleared at the same rate as unmodified hemoglobin, indicating that the adducts are stable in vivo. In contrast, fluoranthene-DNA adducts were not present at detectable levels in liver or kidney 24 h after one dose; low levels of adducts were found only in the lung at the highest dose level. Chronic administration of fluoranthene in the diet, however, resulted in DNA adduct formation in most tissues examined, including liver, kidney, lung, small intestine, heart, spleen and lymphocytes; adducts were not detectable in testes DNA. The major fluoranthene-DNA adduct found in rat tissues was identified by its chromatographic similarity to the major fluoranthene adduct formed in vitro using microsomally-activated fluoranthene and calf thymus DNA, previously identified as a reaction product of anti-2,3-dihydroxy-1,10b-epoxy-1,2,3-trihydro-fluoranthene with N2-deoxyguanosine. The unusual stability of this diol epoxide at physiological pH may allow transport of this ultimate DNA-binding metabolite to virtually all tissues. These results demonstrate the applicability of the HPLC-32P-postlabelling procedure to detect and quantify fluoranthene-DNA adducts formed in vivo, and suggest that analysis of these adducts in accessible tissues such as lymphocytes may be a means of assessing chronic, high level exposure to fluoranthene. Our results also indicate that hemoglobin adducts of fluoranthene could be useful dosimeters for detecting short-term or chronic exposure to this compound if a suitable method for their detection were developed.

Administration, Oral↗