Biological monitoring of o-toluidine in urine pretreated by an enzymatic deconjugation method

OBJECTIVES

To establish an enzymatic deconjugation method to separately quantify urinary o-toluidine (OT), its six metabolites, another six chemicals present in an OT-processing plant, and one metabolite of p-toluidine, and to propose optimal urinary biological monitoring items of OT exposure.

METHODS

Thirty-six urine samples of an OT-processing plant's workers were obtained and pretreated by an enzymatic deconjugation method employing β-glucuronidase/arylsulfatase for 3 hours at 37°C and measured by liquid chromatograph-mass spectrometry (LC-MS). An alkaline hydrolytic pretreatment and 1-chlorobutane extraction procedure was also examined as a widely used urinary OT measurement method.

RESULTS

The 14 chemicals were separated by LC-MS condition set by us and 13 chemicals other than 2-chloroaniline showed satisfiable linearity and limits of determination. Standard substances of six OT metabolites decomposed after the alkaline heating. In the 36 urine samples, OT, N-(4-hydroxy-2-methylphenyl) acetamide (NHM), and 4-amino-m-cresol (ACR) accounted for approx. 90% of the total OT and OT metabolites, but inter-individual variation of the three substance excretion seemed to be wide. Time course of urinary excretion revealed that concentration of the three substances was higher 24 hours after the work shift's end rather than just after the work shift.

CONCLUSIONS

OT and its six metabolites can each be determined with LC-MS. The alkaline method is not so optimal for exact biological monitoring. Rather, the sum of urinary OT, NHM, and ACR measured by the enzymatic method is a better index, and "end of the workweek" is a good urine-sampling time for the biological monitoring of OT exposure.

Environmental determinants of the urinary concentrations of herbicides during pregnancy: the PELAGIE mother-child cohort (France)

Herbicides are generally the most extensively used of the pesticides applied to agricultural crops. However, the literature contains little evidence useful in assessing the potential sources of the general population's exposure to herbicides, including by residential proximity to crops. The objective of this study was to take advantage of data from the PELAGIE mother-child cohort to identify the main determinants of the body burden of exposure to the chloroacetanilide and triazine herbicides commonly used on corn crops in Brittany, France, before 2006. Urine samples from a randomly selected subcohort of women in the first trimester of pregnancy (n=579) were assayed for herbicide metabolites. The residential exposure resulting from proximity to corn crops was assessed with satellite-image-based scores combined with meteorological data. Data on diet, drinking tap water (from the public water supply), occupations, and household herbicide use were collected by questionnaires. Herbicides were quantified in 5.3% to 39.7% of urine samples. Alachlor and acetochlor were found most frequently in the urine of women living in rural areas. The presence of dealkylated triazine metabolites in urine samples was positively associated with residential proximity to corn crops (OR=1.38, 95% CI: 1.05-1.80). Urinary metabolites of both atrazine and dealkylated triazine were correlated with tap water consumption (OR=2.94, 1.09-7.90, and OR=1.82, 1.10-3.03, respectively); hydroxylated triazine metabolites were correlated with fish intake (OR=1.48, 1.09-1.99). This study reinforces previous results that suggest that environmental contamination resulting from agricultural activities may contribute to the general population's exposure to herbicides.

Identification of human urinary metabolites of acetochlor in exposed herbicide applicators by high-performance liquid chromatography-tandem mass spectrometry

Acetochlor is a preemergent chloroacetanilide herbicide used to control annual grasses and small-seeded broadleaf weeds. It is the second most abundantly applied herbicide on corn crops in the United States; however, human metabolites associated with known exposure to acetochlor have not been positively identified and confirmed. We positively identified acetochlor mercapturate (ACM) as a metabolite of acetochlor in urine samples collected during a 24-h period from custom (commercial) applicators who had applied acetochlor on either the day of or the day before urine collection. Concentrations in applicator urine samples ranged from 0.5 to 449 microg/l (0.3-121 microg/g creatinine). We found that ACM accounted for as much as 42% of the total acetochlor-derived metabolites; however, as the exposure level decreased (based on total acetochlor metabolite level), ACM became a less abundant metabolite of acetochlor (<17%). Unmetabolized acetochlor was also measured in the urine samples analyzed. At high exposures (classified as >100 microg/l), acetochlor accounted for about 0.8% of the total excreted acetochlor metabolites (approximately 2% of the ACM concentrations). At lower exposures (classified as ACM<10 microg/l), ACM and acetochlor concentrations were similar. Additionally, we tentatively identified another acetochlor metabolite that appeared to be important at low levels of exposure.

Identification of urinary metabolites of orally administered N,N-dimethyl-p-toluidine in male F344 rats

The metabolism of orally administered N,N-dimethyl-p-toluidine (DMPT) in male F344 rats was investigated. The rat urinary metabolite profile was determined by analytical reverse-phase high performance liquid chromatography (HPLC). Four radiolabeled peaks were observed, isolated, and purified by solid-phase extraction (SPE) and preparative HPLC methods. The 4 peaks were identified as p-(N-acetylhydroxyamino)hippuric acid (M1), DMPT N-oxide (M2), N-methyl-p-toluidine (M3), and parent DMPT. Metabolites M1 and M2 were identified by spectrometric and spectroscopic methods, including mass fragmentation pattern identification from both liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry, and from chemical analysis of nuclear magnetic resonance spectra. Structural confirmation of metabolite M2 was accomplished by comparison with a synthetic standard. Peaks M3 and the peak suspected to be DMPT were identified by comparison of their HPLC retention times and mass fragmentation patterns with authentic standards of N-methyl-p-toluidine and DMPT, respectively. DMPT metabolism is similar to that reported for N,N-dimethylaniline.

Percutaneous absorption of crotamiton in man following single and multiple dosing

PURPOSE

Crotamiton is a topical drug used in the treatment of scabies and pruritus. We determined its percutaneous absorption following single and multiple dosing in normal skin.

METHODS

We used in vivo measurement of percutaneous absorption of [14C] crotamiton in a multidose regimen by measuring urinary excretion and liquid scintillation counting in three groups of four healthy volunteers. The Feldmann urinary excretion method was utilized to ascertain percutaneous absorption. Our results showed that tape stripping does not increase percutaneous absorption of crotamiton; upon repeated application.

Determination of three carcinogenic aromatic amines in urine of smokers and nonsmokers

Aromatic amines (arylamines) such as o-toluidine, 2-aminonaphthalene, and 4-aminobiphenyl occur in the environment and are constituents of tobacco smoke. Human exposure to these aromatic amines has long been associated with an elevated risk of bladder cancer. A validated, specific, and sensitive method for measuring o-toluidine, 2-aminonaphthalene, and 4-aminobiphenyl in cigarette smokers and nonsmokers was developed. The method uses acid hydrolysis of the arylamine conjugates in urine, extraction with n-hexane, derivatization with pentafluoropropionic anhydride, and subsequent analysis with gas chromatography combined with mass spectrometry using negative ion chemical ionization. The limits of detection were 4 ng/L for o-toluidine and 1 ng/L for 2-aminonaphthalene and 4-aminobiphenyl. Smokers (N = 10) excreted significantly higher amounts of o-toluidine (204 versus 104 ng/24 h), 2-aminonaphthalene (20.8 versus 10.7 ng/24 h), and 4-aminobiphenyl (15.3 versus 9.6 ng/24 h) than nonsmokers (N = 10). Urinary arylamine excretion in smokers was associated with the extent of smoking as assessed by daily cigarette consumption, urinary excretion of nicotine equivalents (nicotine plus its five major metabolites), cotinine in saliva, and carbon monoxide in exhaled breath. All nonsmokers investigated had quantifiable amounts of o-toluidine, 2-aminonaphthalene, and 4-aminobiphenyl in their urine, confirming that other environmental sources of exposure to these compounds also occur. In conclusion, the analytical method is suitable for measuring short-term exposure to arylamines in urine of non-occupationally exposed smokers and nonsmokers.

Quantification of six herbicide metabolites in human urine

We developed a sensitive, selective and precise method for measuring herbicide metabolites in human urine. Our method uses automated liquid delivery of internal standards and acetate buffer and a mixed polarity polymeric phase solid phase extraction of a 2 mL urine sample. The concentrated eluate is analyzed using high-performance liquid chromatography-tandem mass spectrometry. Isotope dilution calibration is used for quantification of all analytes. The limits of detection of our method range from 0.036 to 0.075 ng/mL. The within- and between-day variation in pooled quality control samples range from 2.5 to 9.0% and from 3.2 to 16%, respectively, for all analytes at concentrations ranging from 0.6 to 12 ng/mL. Precision was similar with samples fortified with 0.1 and 0.25 ng/mL that were analyzed in each run. We validated our selective method against a less selective method used previously in our laboratory by analyzing human specimens using both methods. The methods produced results that were in agreement, with no significant bias observed.

Effect of dietary fat on selected parameters of toxicity following 1- or 3-month exposure of rats to toluidine isomers

The aim of the study was to investigate the effect of the dietary fat on selected parameters of toluidines toxicity in rats during subchronic exposure. Three isomers of toluidine (ortho, meta, and para) were administered to rats in the diet for 1 and 3 months at levels 40, 80, 160 mg/kg/day in two kinds of diet containing either 4% or 14% fat. All doses of toluidine isomers produced a 1.5- to 9.8-fold increase in methemoglobin (MetHb) level during both treatment periods. A distinct dose-response relationship was observed, especially for o- and m-toluidine; the effect was generally greater in rats fed high-fat diet. Reduced glutathione level in liver was increased in all treated groups, 1.5- to 5.1-fold, irrespective of the kind of diet. An increase in hepatic lipid peroxidation (thiobarbituric acid reactive substances; TBARS), 1.5- to 4.5-fold, was noticed in the majority of the treated groups. Generally, there was no consistent effect of diet except for p-toluidine where the level of hepatic TBARS was lower in rats fed high-fat diet. Blood urea nitrogen (BUN) level in animals treated with all doses of o- and m-toluidine was 1.3- to 5.0-fold higher in comparison with respective controls. No clear relationship between BUN level and the kind of diet was found. No effect of toluidines on the activity of serum aspartate aminotransferase (AST) and sorbitol dehydrogenase (SDH) were observed. In the majority of groups treated for 30 and 90 days the amount of toluidines in 24-h urine was lower in rats fed high-fat diet. Final body weight gain in rats treated with o- and p-toluidine (80 and 160 mg/kg body weight [b.w.]) was lower as compared to controls. In summary the high-fat diet stimulated methemoglobin formation in rats treated with o- and m-toluidine and cause the decrease in the amount of toluidines in 24-h urine. The high content of fat did not affect consistently the other parameters tested.

Development of a method for the detection and confirmation of the alpha-2 agonist amitraz and its major metabolite in horse urine

Amitraz (N'-(2,4-dimethylphenyl)-N-[[(2,4-dimethylphenyl)imino]methyl]-N-methyl-methanimidamide) is an alpha-2 adrenergic agonist used in veterinary medicine primarily as a scabicide- or acaricide-type insecticide. As an alpha-2 adrenergic agonist, it also has sedative/tranquilizing properties and is, therefore, listed as an Association of Racing Commissioners International Class 3 Foreign Substance, indicating its potential to influence the outcome of horse races. We identified the principal equine metabolite of amitraz as N-2,4-dimethylphenyl-N'-methylformamidine by electrospray ionization(+)-mass spectrometry and developed a gas chromatographic-mass spectrometric (GC-MS) method for its detection, quantitation, and confirmation in performance horse regulation. The GC-MS method involves derivatization with t-butyldimethylsilyl groups; selected ion monitoring (SIM) of m/z 205 (quantifier ion), 278, 261, and 219 (qualifier ions); and elaboration of a calibration curve based on ion area ratios involving simultaneous SIM acquisition of an internal standard m/z 208 quantifier ion based on an in-house synthesized d(6) deuterated metabolite. The limit of detection of the method is approximately 5 ng/mL in urine and is sufficiently sensitive to detect the peak urinary metabolite at 1 h post dose, following administration of amitraz at a 75-mg/horse intravenous dose.

Biological monitoring of phenmedipham: determination of m-toluidine in urine

Phenmedipham [methyl-3-(3-methylphenylcarbamoyloxy)carbamate] is used as a herbicide, especially in the growing of sugar beet and strawberries. During metabolism of the substance in rats, the two carbamate moieties of phenmedipham are cleaved and the metabolites methyl-N-(3-hydroxyphenyl)-carbamate, m-aminophenol and hydroxyacetanilide are formed. These compounds and their conjugates are excreted in urine. Additionally, it has been suggested that m-toluidine is formed during metabolism. For the first time it has been possible to detect this metabolite in the urine of workers after agricultural use of phenmedipham. The concentrations of m-toluidine in urine were significantly higher in persons occupationally exposed than in controls. The median values for each group were 0.36 microg/l and 0.16 microg/l, respectively. This means that persons not exposed to phenmedipham also excrete m-toluidine, possibly as a result of the uptake of pesticides like phenmedipham from the diet.

Gas chromatographic method for the determination of toluidines in spiked urine samples

A capillary gas-chromatographic method was developed for the analysis of a mixture of toluidines in urine. The method is based on the extraction of toluidines with toluene and derivatisation with heptafluorobutyric anhydride to form a product for electron capture detection. The procedure gave a linear response at concentrations of 0.02-0.20 microg/ml with sufficient reproducibility. The method is simple, requires little sample pretreatment and is being considered for biomonitoring workers exposed to toluidines.

In vivo percutaneous absorption of acetochlor in the rhesus monkey: dose-response and exposure risk assessment

Percutaneous absorption of three topical dose levels of [14C]acetochlor in the rhesus monkey were determined for exposure risk assessment. The topical doses were 30.7, 0.43 and 0.03 mg acetochlor in 40 microliters commercial formulation and aqueous dilutions thereof, spread over 10 cm3 skin surface area (lower abdominal). The dosing area was not covered. The skin application time was 24 hr. The dosed skin surface area was washed with 50% soap (Ivory Liquid) and water at the end of the 24-hr dosing period. An intravenous dose of 0.43 mg was also administered to determine the excretory kinetics of acetochlor in the rhesus monkey. The same four monkeys were used for all dose administrations. Bioavailability was determined by radioactivity disposition in blood, urine and faeces. Percutaneous absorption was 23.1 +/- 8.7, 17.3 +/- 5.9 and 4.9 +/- 1.4% for 0.03, 0.43 and 30.7 mg doses, respectively. Assuming a constant state of absorption, the hourly exposure flux (microgram/cm2/hr) was 0.03 +/- 0.01 for the 0.03 mg dose (3 micrograms/cm2). Increasing the dose approximately 15-fold to 0.43 mg (43 micrograms/cm2) resulted in a 10-fold increase in flux to 0.3 microgram/cm2/hr. Increasing the dose a further 70-fold to 30.7 mg (3070 micrograms/cm2) resulted in only another 21-fold increase in flux (6.3 +/- 1.8 micrograms/cm2/hr). Thus, the efficiency of absorption (%) decreased with increased topical dose, but the amount (mass/flux) of acetochlor absorbed always increased with increased dose. Plasma levels of topical acetochlor at the high dose were detectable at 1 hr and continued at a relatively steady level through the 24-hr dosing period. After the skin surface wash (24 hr) plasma levels decreased but were still detectable at the last 168-hr sampling period. Acetochlor, recently EPA approved as an herbicide for corn crops, is carcinogenic; however, farmers will use half as much acetochlor/acre as other herbicides. The percutaneous absorption of acetochlor is equal to that of alachlor. Therefore, human exposure based on one-half usage suggests that human risk assessment should be one-half all other factors being equal.

Monitoring of aromatic amine exposures in workers at a chemical plant with a known bladder cancer excess

BACKGROUND

In April 1991, an excess of bladder cancer cases among workers employed at a chemical manufacturing facility in Niagara Falls, NY, was reported. This excess was primarily confined to 708 workers who had ever been employed in the rubber chemicals manufacturing area of the plant, where the aromatic amines aniline and o-toluidine have historically been used.

PURPOSE

An environmental and biological monitoring survey was conducted to evaluate current exposures to aniline and o-toluidine in the rubber chemicals department.

METHODS

Personal air sampling for aniline and o-toluidine was conducted with the use of a modified Occupational Safety and Health Administration (OSHA) 73 method. Urine samples were collected before and after work (i.e., pre-shift and post-shift, respectively) and stored at -70 degrees C. Base hydrolysis was used to convert acetanilide and N-acetyl-o-toluidine, metabolites of aniline and o-toluidine present in the urine, to the parent compounds. The parent compounds were extracted from the alkaline urine into butyl chloride and then back-extracted from the butyl chloride into aqueous hydrochloric acid. An aliquot of each acidic extract was subjected to ion-interaction reversed-phase liquid chromatography with coulometric electrochemical detection. Hemoglobin (Hb) was extracted from blood and stored at -70 degrees C. For the measurement of adducts of aniline, o-toluidine, and 4-aminobiphenyl (4-ABP), precipitated Hb was dissolved in 0.1 M sodium hydroxide in the presence of recovery standards, and the hydrolysate was extracted with hexane, derivatized with pentafluoropropionic anhydride, and analyzed by gas chromatography-mass spectrometry with negative chemical ionization.

RESULTS

A total of 73 workers, including 46 of 64 exposed workers who were employed in the rubber chemicals department and had the potential for exposure to aniline and o-toluidine and 27 of 52 unexposed workers employed in other departments where aniline and o-toluidine were not used or produced, had data available for both aniline and o-toluidine and Hb adducts; 28 of the workers in the former group also had personal air-sampling data. Personal air sample measurements showed that airborne concentrations of aniline and o-toluidine were well within the limits allowed in the workplace by OSHA. Urinary aniline and o-toluidine levels, however, were substantially higher among exposed workers than among unexposed control subjects. The most striking differential was for post-shift urinary o-toluidine levels, which averaged (+/- standard deviation) 2.8 micrograms/L (+/- 1.4 micrograms/L) in unexposed subjects and 98.7 micrograms/L (+/- 119.4 micrograms/L) in exposed subjects (P = .0001). Average aniline-Hb and o-toluidine-Hb adduct levels were also significantly higher (P = .0001) among exposed workers than among unexposed control subjects. Average levels of adducts to 4-ABP, a potential contaminant of process chemicals, were not significantly different (P = .48), although three exposed workers had 4-ABP levels above the range in unexposed workers.

CONCLUSIONS

The adduct data suggest that, among current workers, o-toluidine exposure substantially exceeds aniline exposure and that 4-ABP exposure, if it occurs at all, is not widespread. These data support the conclusion that occupational exposure to o-toluidine is the most likely causal agent of the bladder cancer excess observed among workers in the rubber chemicals department of the plant under study, although exposures to aniline and 4-ABP cannot be ruled out.

Development of a biomonitoring assay for ortho-toluidine or its metabolites in human urine

We describe a method for the measurement of a metabolite of ortho-toluidine in urine. The method uses capillary gas chromatographic separation with mass spectrometric detection to quantitate the metabolite, and it requires no derivatization or extraction of the urine sample prior to analysis. Quantitation is accomplished by comparison with a control spiked with a standard of the metabolite. The coefficient of variation for day-to-day reproducibility of the assay was 9.7%. The limit of quantitation was 10 micrograms/L (10 parts per billion).

Gas chromatographic/tandem mass spectrometric identification and quantitation of metabolic 4-acetyltoluene-2,4-diamine from the F344 rat

2,4-Toluenediamine (TDA) and 2,4-toluenediisocyanate (TDI) are metabolized in the Fischer 344 rat to monoacetyl-2,4-toluenediamine (Ac-TDA) and diacetyl-2,4-toluenediamine (Ac2-TDA). A gas chromatographic/tandem mass spectrometric (GC/MS/MS) method was developed to characterize the structure of the Ac-TDA metabolite (2-acetyl versus 4-acetyl), as a D3-diacetyl-TDA derivative. This method was also shown to be useful in the measurement of urinary levels of TDA, Ac-TDA and Ac2-TDA. Urine samples (1.0 g) were adjusted to pH 6.5-7.0, fortified with the internal standard D9-Ac2-TDA (D3-ring + D3-acetyl x 2) and extracted with ethyl acetate (2 x 2 ml). The extract residues were then derivatized with D6-acetic anhydride and analyzed via electron impact GC/MS/MS. MS/MS analysis of the D3-Ac2-TDA derivative of the two Ac-TDA isomers yielded different daughter ion spectra from the common parent ion (m/z 209). Analysis of urine samples from rats administered TDA (p.o., i.v.) and TDI (p.o., inhalation) indicated that all of the metabolic Ac-TDA from these test materials was the 4-acetyl-TDA isomer. Subsequent GC/MS analysis of the heptafluorobutyric acid (HFBA) derivative of this metabolite confirmed the MS/MS results. Selected ion monitoring of the M-acetyl daughter ions from the derivatized TDA, Ac-TDA and Ac2-TDA was shown to be a useful technique for quantitation of urinary levels of these compounds, with a detection limit of 35 ng g-1 urine for TDA and 10 ng g-1 urine for Ac-TDA and Ac2-TDA.

Biological monitoring for occupational exposures to o-toluidine and aniline

Epidemiological evidence that occupational exposure to o-toluidine and aniline is associated with an increased risk of bladder cancer led to efforts to identify biomarkers of workplace exposures to these aromatic amines. For the determination of o-toluidine and aniline in worker urine specimens, a method using high performance liquid chromatography (HPLC) followed by electrochemical detection was developed. The limits of detection were 0.6 microgram/l and 1.4 micrograms/l for o-toluidine and aniline, respectively. Recovery of o-toluidine and aniline from spiked urine averaged 86% and 93%, respectively, over a range of 4-100 micrograms/l. Reproducibility in the range 2-100 micrograms/l for analyses of split field samples was 13% (average RSD) for o-toluidine and 16% (average RSD) for aniline. Application of this method to pre- and post-shift samples collected from potentially exposed and unexposed workers indicated elevated concentrations of o-toluidine and aniline in urine from exposed workers. To develop methods for biomarkers of internal dose, o-toluidine binding to the blood proteins hemoglobin and albumin was investigated utilizing in-vivo (rodent) and in-vitro (hemoglobin and albumin) studies. Base-hydrolyzable protein adducts were analyzed by HPLC (fluorescence) and/or GC/electron capture (EC). The methods were compared for sample preparation requirements, selectivity and sensitivity. While the GC/EC method was more sensitive than HPLC, the presence of interfering peaks limited the utility of this approach. Results from these studies suggested that the HPLC method could be useful for determination of o-toluidine exposures in individuals acutely or chronically exposed to high levels.

HPLC determination of the metabolite 4-chloro-o-toluidine in the urine of workers occupationally exposed to chlordimeform

A reversed phase HPLC method (UV detection) is described or the analysis of 4-chloro-o-toluidine in the urine of workers occupationally exposed to chlordimeform. The procedure involves extracting an alkaline hydrolysate of urine with hexane, evaporating off the solvent, and reconstituting the residue with an aqueous acetonitrile mobile phase.

Identification and quantitative determination of aniline and toluidines in human urine

Aniline and o-, m-, and p-toluidine, which are representative of aromatic amines in cigarette smoke, were identified and quantified in human urine. Smokers excreted 3.1 +/- 2.6 micrograms/24 h of aniline and 6.3 +/- 3.7 micrograms/24 h of o-toluidine (n = 16). Nonsmokers excreted 2.8 +/- 2.5 micrograms/24 h of aniline and 4.1 +/- 3.2 micrograms/24 h of o-toluidine (n = 12). Meta- and p-toluidine were detected in the urine of 2 of 11 smokers and 4 of 9 nonsmokers. The observed intra- and interindividual variations in the amounts of urinary aniline and o-toluidine were relatively large. The results of this study demonstrate for the first time that aniline and toluidines are present in human urine and suggest that sources other than cigarette smoke contribute significantly to their concentrations in urine.

Identification of urinary metabolites of 2,4,6-trinitrotoluene in rats by liquid chromatography-mass spectometry

Metabolites of 2,4,6-trinitrotoluene (TNT) were found in the urine of rats fed with TNT. The urine extracts were analysed by liquid chromatography-mass spectrometry (LC-MS). Metabolites found included TNT itself as well as 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene and 2,4-diamino-6-nitrotoluene, indicating that reduction processes are responsible for the formation of these metabolites.

Estimation of N-hydroxy-o-toluidine, a urinary metabolite of o-toluidine and o-nitrosotoluene, by high performance liquid chromatography with electrochemical detection

High-performance liquid chromatography with electrochemical detection, a highly sensitive and specific method, was used to determine N-hydroxy-o-toluidine and o-toluidine in the urines of male F344 rats after the administration of 0.82 mmol/kg of o-toluidine or o-nitrosotoluene. In a six hour period, 0.11% of the dose was excreted by o-toluidine-treated rats as N-hydroxy-o-toluidine and 3.61% as o-toluidine. In the same period, 0.48% of the dose was excreted by o-nitrosotoluene treated rats as N-hydroxy-o-toluidine and 0.38% as o-toluidine. The urinary excretion of the N-hydroxy-o-toluidine metabolite may play a role in the carcinogenicity of o-nitrosotoluene and o-toluidine toward the rat bladder.

Comparison of the metabolism of 2,4-toluenediamine in rats and mice

The excretion, distribution, and metabolism of 2,4-toluenediamine (TDA) have been compared in rats and mice. The elimination of TDA metabolites into urine was faster and more complete in mice than in rats. However, the feces of rats accounted for a greater percentage of the dose in rats than in mice. The distribution of metabolites in tissues were considerably lower in mice than in rats. The major urinary metabolites observed in the rat were 4-acetylamino-2-aminotoluene, 2,4-diacetylaminotoluene, 4-acetylamino-2-aminobenzoic acid. The major metabolites in the mice were 4-acetylamino-2-aminobenzoic acid, 4-acetylamino-2-aminotoluene and 2,4-diacetylaminobenzoic acid.

Liver and lung tumors in dogs from 4,4'-methylene-bis(2-methylaniline)

Six female beagle dogs were given, by capsule, a daily dose of 100 mg 4,4'-methylene-bis(2-methylaniline) (MeMDA), 3 times per week for 6 weeks, then 5 times per week for 5 weeks, at which time the dose was reduced to 50 mg 5 times per week, continuously for periods up to 7.0 years. Six female beagle dogs were kept as untreated controls for several studies and were sacrificed after 8.3 to 9 years test. MeMDA dogs developed renal atrophy with an elevated blood urea nitrogen during an approximate six-month period prior to death or being sacrificed in extremis. As three of three MeMDA dogs that survived for 5.2 years to 7.0 years developed hepatocellular carcinomas and two of the three dogs also developed primary lung tumors, with no liver or lung tumor in six control dogs, MeMDA was considered to be carcinogenic for the dog (liver tumors: p less than .05; lung tumors: p less than 10; Fisher's Exact Test, one tail).