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At least 19 recordsLinked to original sources
PubMed1990

Biomonitoring of aromatic amines. III: Hemoglobin binding of benzidine and some benzidine congeners.

Covalent binding of benzidine and some congeners to hemoglobin was studied in female Wistar rats after oral administration. Hemoglobin adducts were hydrolyzed under alkaline conditions, and the arylamines extracted and analysed by HPLC with electrochemical detector. With benzidine, three cleavage products were observed, the major component being monoacetylbenzidine. This indicates that 4-nitroso-4'-N-acetylaminobiphenyl is the major reactive metabolite in erythrocytes. In addition benzidine and 4-aminobiphenyl were identified. The latter indicates a hitherto unknown metabolic pathway of benzidine. With 3,3'-dichlorobenzidine-dihydrochloride, 3,3'-dimethoxybenzidine and 3,3'-dimethylbenzidine two cleavage products were observed, the parent diamines being present in excess to or in amounts comparable to the monoacetyl derivative. With 3,3',5,5'-tetramethylbenzidine a hemoglobin adduct could not be found. When the azo dye direct red 28 was administered to the animals, the three cleavage products typical for benzidine were found, indicating that benzidine became bioavailable after reductive cleavage of the azo compound. In this case the fraction of 4-aminobiphenyl was greater than after benzidine. It is proposed to use the analysis of hemoglobin adducts in human blood to control the exposure of individuals to these carcinogenic chemicals in the course of biochemical effect monitoring.

Administration, Oral↗
PubMed1991

Conjugates of benzidine with a ternary phenol-containing copolymer of N-vinylpyrrolidone as test antigens for the detection of benzidine in human serum.

Water-soluble polymeric amide and azo derivatives of benzidine, based on the terpolymer N-vinylpyrrolidone-crotonic acid-p-crotonoylaminophenol, which possesses adjuvant activity, were synthesized. By means of a double diffusion reaction in agar and a complement-binding reaction it was found that immunization of rabbits with the benzidine-polymer antigens (with or without complete Freund's adjuvant) led to the formation of highly specific antibodies against the hapten benzidine. Sera from rabbits immunized with these conjugates of benzidine may thus be used for the detection of benzidine in the sera of workers exposed to this chemical.

Animals↗
PubMed1975

Metabolic reduction of benzidine azo dyes to benzidine in the rhesus monkey.

Rhesus monkeys were fed azo dyes derived from benzidine (a known human bladder carcinogen). The urinary excretion of free benzidine was assayed and compared to the amount excreted when benzidine itself was fed. A substantial amount of the dye fed was converted to free benzidine. Results indicate that the simple precaution in the use of only azo dyes manufactured from noncarcinogenic aromatic amines, e.g., aniline, for all consumer products appears prudent.

Aminobiphenyl Compounds↗
PubMed1992

Role of N-glucuronidation in benzidine-induced bladder cancer in dog.

The mechanism by which benzidine induces bladder cancer in dog was evaluated by assessing metabolism of [3H]benzidine by dog liver slices and microsomes. Slices incubated with 0.05 mM [3H]benzidine exhibited a 32.5 min incubated with 0.05 mM [3H]benzidine exhibited a 32.5 min peak, which was also produced when microsomal incubations were supplemented with UDP-glucuronic acid. In contrast to microsomes, very little of the 32.5 min peak was produced with the 100,000 g supernatant fraction. Microsomal metabolism was increased 5-fold by pretreatment with Triton X-100. Very little activity was observed with rat microsomes in either the presence or absence of Triton X-100. This metabolite was also generated by incubating benzidine with glucuronic acid at 4 degrees C for 3 days. Thermospray MS identified this metabolite as benzidine N-glucuronide. At 37 degrees C, the t1/2 stability of purified N-glucuronide was 99, 25 and 3 min in dog urine adjusted to pH 7.3, 6.3 and 5.3 respectively. The N-glucuronide was quite stable at pH 9.3, in dog plasma, and in aprotic solvents for 4 h at 37 degrees C. Relative to benzidine, its N-glucuronide is weakly bound to plasma proteins but not more reactive with DNA. Thus, detoxification by liver provides a mechanism for accumulation of benzidine in acidic urine, uptake of benzidine into bladder epithelium, and activation of benzidine in bladder. The liver and N-glucuronidation play a potentially important role in the species specificity of benzidine carcinogenesis.

Animals↗
PubMed1990

Mechanism of peroxidative activation of the bladder carcinogen 2-amino-4-(5-nitro-2-furyl)-thiazole (ANFT): comparison with benzidine.

The mechanism of activation of the bladder carcinogen 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT) was investigated by comparison with benzidine. In comparison with benzidine, ANFT has a higher electrochemical potential (approximately 700 mV) and is less effective as a reducing co-substrate for either prostaglandin H synthase (PHS) or horseradish peroxidase. Activation was monitored by measuring binding to protein (BSA) and DNA. ANFT binding to protein was reduced by indomethacin, a fatty acid cyclooxygenase inhibitor; phenol and aminopyrine, competitive reducing co-substrates; ascorbic acid, an antioxidant; and glutathione, thioether conjugate formation. These results are consistent with those previously reported for benzidine and demonstrate a peroxide co-substrate requirement, interaction of peroxidase with amine, formation of reactive intermediates and inactivation of reactive intermediates. 5,5-Dimethyl-1-pyrroline N-oxide (DMPO), a radical trap, also reduced ANFT binding to protein. Similar results were observed whether activation by PHS or horseradish peroxidase was investigated. Peroxidative activation of ANFT and benzidine to bind DNA was inhibited by these test agents in a manner similar to that observed with protein except that DMPO did not reduce binding. In addition, 2-methyl-2-nitrosopropane and methyl viologen, which are radical traps, and methionine and p-nitrobenzyl-pyridine, which are strong nucleophiles, did not reduce ANFT or benzidine binding to DNA. These agents also did not prevent binding of benzidinediimine, the two-electron product of benzidine oxidation, to polydeoxyguanosine. Glutathione inhibited diimine binding by forming a conjugate. Results demonstrate that activation of ANFT to bind protein and DNA is similar to benzidine. Peroxidative activation of benzidine occurs by both one- and two-electron oxidation. A similar mechanism would explain ANFT binding to protein (one electron) and DNA (two electron).

Alkenes↗
PubMed1975

Factors modulating benzidine carcinogenicity bioassay.

An integrated series of studies was presented in which several factors were assessed as to their capability to influence the outcome of carcinogenicity of benzidine dihydrochloride in mice. In all studies C57BL/6J X C3HeB/FeJ F1 mice of both sexes were utilized. Animals were either 6 or 1 week of age at the beginning of carcinogenic treatment. Six-week-old mice were exposed to p.o. administration of carcinogen delivered either in food (50 or 100 ppm daily) or by stomach intubation at equivalent dose levels at twice-weekly intervals. In addition, a 150-ppm dose level in food was administered for 39, 54, or 84 weeks. A limited 3-week, daily intubation of benzidine (30 or 100 mug/mouse) was also explored in 1- and 6-week-old mice. Animals were killed in all studies at 90 weeks of age, at which time their tumor incidence was evaluated. Depending upon experimental conditions, benzidine treatment effected development of liver tumors, lung adenomas. Harderian gland cystadenomas, and lymphoreticular neoplasms. Continuous feeding of adult mice for 84 weeks at three dose levels of benzidine resulted in development of liver tumors with a positive dose-response relationship in both sexes. The analysis of data revealed a greater susceptibility of females than of males (94% versus 44% at 150 ppm). Twice-weekly administration of benzidine by stomach intubation was shown to be less hepatocarcinogenic than continuous feeding of equivalent amounts. In the series in which male mice were fed food containing 150 ppm of benzidine for only 34 or 54 weeks, in contrast to the above 84-week schedule, a negative relationship was observed between the incidence of liver tumors and the duration of treatment. Daily administration of 30 mug of benzidine to infants by stomach intubation for a 3-week period significantly enhanced development of liver tumors only in males (66%). Introduction of 150 ppm of benzidine into food offered to mother and offspring from delivery to weaning led to development of liver tumors in 95% of male mice and in 5% of females. No liver tumors developed following similar 3-week treatment of 6-week-old adults.

Administration, Oral↗
PubMedDate not supplied

Mutagenic activation of benzidine requires prior bacterial acetylation and subsequent conversion by prostaglandin H synthase to 4-nitro-4'-(acetylamino)biphenyl.

We have used the Ames test in combination with prostaglandin H synthase (PHS) to study the bioactivation of benzidine as well as other aromatic amines. Previous investigations established that the formation of benzidine mutagens by PHS is dramatically enhanced in Salmonella typhimurium strains with high levels of acetyl CoA-dependent arylamine N-acetyltransferase/arylhydroxylamine O-acetyltransferase activity despite the fact that acetylation of aromatic amines decreases their susceptibility to oxidation by peroxidases. In this study, we used a new strain (YG1012) that has very high acetylation capability to investigate the metabolism and mutagenicity of benzidine and N-acetylbenzidine catalyzed by PHS (from ram seminal vesicle microsomes) and horseradish peroxidase (HRP). YG1012 bacteria rapidly acetylated benzidine to N-acetylbenzidine and N,N'-diacetylbenzidine. Preincubation of the bacteria with benzidine before addition of PHS increased the mutagenicity. Under conditions identical to those used to assess mutagenicity, PHS metabolized benzidine rapidly, but the substrate was not totally consumed, with about 40% of the original concentration remaining intact. These data suggest that conversion to N-acetylbenzidine may be the initial step in the bioactivation of benzidine in the PHS-mediated Ames assay. N-Acetylbenzidine is a cosubstrate for PHS peroxidase activity as measured by 5-phenyl-4-pentenyl hydroperoxide reduction, spectral changes, and formation of protein adducts. N-Acetylbenzidine was converted to mutagens by PHS but not HRP, with enhanced mutagenicity observed in bacteria with high acetylation activity. We used reverse- phase HPLC to characterize the metabolites of N-acetylbenzidine formed by PHS and HRP.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetamides↗
PubMed1990

Metabolism and disposition of benzidine in the dog.

The dog is an animal model for assessing aromatic amine-induced bladder cancer. For this reason, metabolism and disposition of benzidine in dog was assessed. Dogs were administered a 1 mg/kg i.v. dose of [3H]benzidine (16.4 mCi/mmol). The plasma t1/2 of the radiolabeled material (benzidine plus metabolites) was significantly longer (approximately 3 h) than authentic benzidine (less than 30 min). During the 5 h experiment, the majority of radiolabel was associated with bile, urine and carcass. Bladder transitional epithelium exhibited a consistently higher concentration of bound radioactivity than bladder muscle. A significant amount of binding was observed in DNA from liver, kidney and bladder. DNA from bladder transitional epithelium exhibited the highest concentration of radioactivity. Approximately 30% of the radioactivity recovered following HPLC of urine or bile was identified as unmetabolized benzidine. 3-Hydroxybenzidine was a major metabolite identified in bile (8%) but not urine. Urine samples treated with acid, base or sulfatase yielded 3-hydroxybenzidine (6%) as a major hydrolysis product. Similar treatment of bile samples did not result in increased amounts of 3-hydroxybenzidine. Neither N-acetylated nor N-methylated metabolites of benzidine were observed in urine or bile. Thus, considerable metabolism of benzidine occurs in dogs by pathways that are yet to be determined.

Animals↗
PubMed1990

Studies on the relation between bladder cancer and benzidine or its derived dyes in Shanghai.

Shanghai is the largest industrial centre in China and has a history of about 50 years in producing and applying benzidine derived dyes. A series of epidemiological studies on the carcinogenicity of benzidine and its derived dyes have been performed since 1979. This report describes three such studies. A case-control study was carried out on 344 cases of bladder cancer, each matched for age and sex, with a person without bladder cancer. Factors studied were occupational exposure, smoking, drinking, medical histories, and family history of bladder cancer and other carcinomas. The correlation between bladder cancer and occupational exposures (relative risk (RR) 5.71) was greater than that between bladder cancer and smoking (RR 1.53). A retrospective cohort study was conducted in seven dyestuffs factories where benzidine had served as an intermediate in the manufacture of dyes before 1976. The cohort was made up of 550 men and 186 women. The men were divided into two groups according to job; 354 were assigned to a presynthesis group and 196 to a postsynthesis group. Those in the presynthesis group were thought to have been exposed to benzidine and the subjects in the postsynthesis group were exposed mainly to its derived dyes. The 15 cases of bladder cancer diagnosed were all in the presynthesis group, although an excess of bladder cancer was also seen in the whole cohort. The standardised incidence ratio (SIR) of bladder cancer was 1918 in the whole cohort and 3500 in the presynthesis group. Moreover, the SIR of bladder cancer in a subgroup working directly with the assignment, transport, and mixing of benzidine was as high as 7500. A further retrospective cohort study was made on incidence of cancer among 1420 workers who used benzidine derived dyes in 43 textile printing and dyeing factories. No excess carcinoma was found. These results suggest that, in Shanghai, the main cause of bladder cancer is occupational exposure, especially to benzidine. The risk of bladder cancer, however, existed only in the presynthesis stage of dye manufacture.

Benzidines↗
PubMed1989

Prostaglandin H synthase-dependent mutagenic activation of benzidine in a Salmonella typhimurium Ames tester strain possessing elevated N-acetyltransferase levels.

Watanabe and colleagues (Biochem. Biophys. Res. Commun. 147: 974-979, 1987) have constructed plasmid-containing derivatives of Salmonella typhimurium Ames tester strain TA1538 with high levels of acetyltransferase activities. In this paper, we describe the mutagenic response of one of these strains, TA1538/1,8-DNP6 (pYG 121), to the bladder carcinogen benzidine and other arylamines. Strain TA1538/1,8-DNP6 (pYG 121) was far more sensitive to benzidine than any previous tester strain, following metabolism of the aromatic amine by hamster hepatic S9, ram seminal vesicle microsomal preparation (RSVM), or purified prostaglandin synthase. Therefore, bacterial acetyltransferase-dependent metabolism of a proximate mutagen is implicated in each of these systems. The mechanism of RSVM-dependent activation of benzidine was examined further. The arachidonic acid-independence and indomethacin insensitivity previously noted with strain TA98 were also observed with the new tester strain. We confirmed that prostaglandin H synthase is the enzyme activity responsible for activation of benzidine by RSVM. Purified prostaglandin H synthase holoenzyme, or apoenzyme reconstituted with heme, supported benzidine activation. However, apoenzyme reconstituted with manganese protoporphyrin IX, which yields enzyme having cyclooxygenase activity but not peroxidase activity, was inactive. Addition of catalase inhibited, and addition of exogenous hydrogen peroxide increased, RSVM-mediated benzidine mutagenicity. We propose that hydrogen peroxide released by the tester strain bacteria (rather than arachidonic acid-derived peroxide) is the oxidizing agent which supports prostaglandin H synthase peroxidase activity in Ames test systems.

Acetyltransferases↗
PubMed1992

Mortality and incidence of bladder cancer in benzidine-exposed workers in China.

We examined bladder cancer mortality and incidence to 1981 in 1,972 workers employed in benzidine-exposed jobs in Tianjin, Shanghai, and Jilin, China, between 1972 and 1977, and in 1,974 unexposed workers employed during the same time period. In comparison to general population rates, in the benzidine-exposed group the ratio of observed to expected deaths (SMR) was 17.5 (95% C.I.: 7.5-34.5) and the ratio of observed to expected incident cases (SIR) was 25.0 (95% C.I.: 16.9-35.7). No excess was noted in the unexposed group. The 25-fold increase in bladder cancer incidence in the exposed group was related to level of exposure, with the SIR rising from 4.8 for low exposure to 36.2 for medium exposure, and 158.4 for high exposure. Risks were elevated both for producers of benzidine (SIR = 45.7; 95% C.I.: 20.9-86.8) and for users (SIR = 20.9; 95% C.I.: 12.9-32.0) of benzidine dyes. Benzidine-exposed workers who smoked tobacco had a 31-fold risk (95% C.I.: 20.4-46.4), while non-smoking workers had an 11-fold risk (95% C.I.: 3.6-25.8), suggestive of a multiplicative relationship between these two carcinogens.

Air Pollutants, Occupational↗
PubMed1987

Peroxidative metabolism of benzidine derivatives by Salmonella typhimurium.

Benzidine and several derivatives are activated to mutagenic species in an H2O2-dependent Ames test system. Optical and electron paramagnetic resonance (EPR) spectroscopy are employed in studies of the H2O2-dependent oxidation of benzidine and 3,5,3',5'-tetramethylbenzidine (TMB) catalyzed by intact bacteria, and provide direct evidence for peroxidase activity in Salmonella typhimurium. The acetylase-proficient Ames tester strain TA98 and its acetylase-deficient derivative TA98/1,8-DNP6 are equally responsive to H2O2-dependent mutagenicity; enzymatic acetylation appears not to be involved in activation of benzidine, in this system. The H2O2-dependent mutagenicity of benzidine and oxidation of TMB are observed when the assays are carried out in acetate buffer (pH 5.5), but not in 2-[N-morpholino]ethane sulfonic acid (MES) buffer, at the same pH. This difference is interpreted in terms of the effects of these buffers on the intracellular pH of the bacteria. The H2O2-dependent mutagenicity of several benzidine congeners is also described.

Benzidines↗
PubMed1989

Binding of chlorinated benzidines to the rat hepatic aromatic hydrocarbon receptor.

The binding of benzidine, 3,3'-dichlorobenzidine (3,3'-Cl2BZ), and the asymmetrically-substituted chlorinated benzidines 3,5-dichlorobenzidine (3,5-Cl2BZ) and 3,5,3'-trichlorobenzidine (Cl3BZ) to the rat hepatic cytosolic aromatic hydrocarbon (Ah) receptor was measured, in order to assess the mechanism of P-450I induction by 3,3'-Cl2BZ. Cl3BZ is the most mutagenic benzidine derivative in the Ames assay. Binding affinity to the Ah receptor protein was determined by displacement of labelled 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) from the receptor, measured with the sucrose density gradient centrifugation technique. The rank order of affinities and the apparent inhibitor constants were: Cl3BZ (4 microM) greater than 3,5-Cl2BZ (8.4 microM) greater than 3,3'-Cl2BZ (10 microM). Benzidine did not displace TCDD from the receptor protein. 4-Aminobiphenyl a structural link between the benzidine and biphenyl series competed weakly with TCDD. The 50% inhibition concentration was about 150 microM. The results are consistent with the hypothesis that the induction of P-450 enzymes by 3,3'-Cl2BZ in vivo is mediated by the Ah receptor.

3,3'-Dichlorobenzidine↗
PubMed1989

[Benzidine dyes and risk of bladder cancer].

Until the early 1970's there was little concern about dyes which contain benzidine as an integral part of their chemical structure. Furthermore, use of the finished dyes was not considered dangerous. To ascertain whether azo dyes are associated with risk of development of bladder tumors in workers who handpaint Yuzen-type silk kimonos in Kyoto, we investigated the disintegration of dyes to benzidine. In these studies, we found that in rats and mice benzidine-based dyes are metabolized to benzidine and that the azo linkage of benzidine dyes is reduced by Escherichia coli and soil bacteria. These experimental findings were reported previously. In this report, we outline an approach to these studies. Many of the dyes used to color paper, textiles, lipstick, bait used by fishermen, as well as hair dyes, and dyes used in research, for pharmaceutical products, and by defence personnel for the detection of liquid chemical warfare agents, have been shown to be potentially mutagenic or carcinogenic. We review the literature on these dyes.

Animals↗
PubMed1979

Tetramethylbenzidine--a substitute for benzidine in hemoglobin analysis.

Plasma hemoglobin is routinely measured by some modification of the benzidine-hydrogen peroxide method, particularly at low concentrations. Because benzidine is carcinogenic, and thus impractical for clinical use under current restrictions, the identification of a noncarcinogenic benzidine derivative has become important. 3,3',5,5'-tetramethylbenzidine fulfills this criterion, and consequently a method is described in this paper which uses it for hemoglobin determinations in the range of 1 to 100 mg/dl. Absorption spectra show this method to be far less influenced by plasma proteins and other substances than the benzidine method, and moreover the sensitivity of TMB is at least seven times that of benzidine under comparable conditions.

Benzidines↗
PubMedDate not supplied

Activity of the human carcinogens benzidine and 2-naphthylamine in triple- and single-dose mouse bone marrow micronucleus assays: results for a combined test protocol.

The activities of the human bladder carcinogens benzidine and 2-naphthylamine in the mouse bone marrow micronucleus assays using a limited test protocol (oral dosing to male mice, sampling 24 h later) have recently been established. As a contribution to the International Collaborative Study on the evaluation of the sensitivity of the triple-dose micronucleus test protocol it was decided to re-evaluate benzidine and 2-naphthylamine using a combined triple- and single-dose test protocol. Benzidine gave a clear positive response in male mice 24 h after 3 daily doses of 150 and 300 mg/kg. A single dose of 900 mg/kg of benzidine gave a weaker response 24 h after dosing. In the case of 2-naphthylamine a stronger positive response was observed 24 h after a single dose of 600 mg/kg as compared to 3 daily doses of 200 or 400 mg/kg. There was no significant difference in the increased positive response observed for a single dose of 30 mg/kg of cyclophosphamide compared with 3 successive daily doses of 10 mg/kg. Based on the present data the combined triple/single-dose micronucleus test protocol is strongly supported.

2-Naphthylamine↗