Effect of alpha-naphthylisothiocyanate on blood clearance of 99mTc-phytate in dogs

The effect of alpha-naphthylisothiocyanate (ANIT) on blood clearance of 99mTc-phytate (99mTc-P) in dogs was examined, and blood clearance test of 99mTc-P was compared with the cases of serum transaminase test or serum bilirubin test. Serum transaminase and bilirubin levels in dogs increased after ANIT administration, however, the degree of increase in these parameters was much lower than the cases in rats. The disappearance rate of 99mTc-P from blood in dogs decreased with the increase in dose of ANIT and with the passage of time after the ANIT administration. Changes of the blood clearance of 99mTc-P after ANIT treatment in dogs may be influenced by the disorder in the hepatocytes rather than in the bile ductule cells. The blood clearance test of 99mTc-P in dogs showed a sensitive reaction for the acute hepatic dysfunction induced by ANIT equally to the serum transaminase test or the serum bilirubin test.

Effect of alpha-naphthylisothiocyanate on blood clearance of 99mTc-phytate in rats

The effect of alpha-naphthylisothiocyanate (ANIT) on blood clearance of 99mTc-phytate (99mTc-P) in rats was examined, and blood clearance test of 99mTc-P was compared with the cases of serum transaminase test, serum bilirubin test or histological test of the liver. The disappearance rate of 99mTc-P from blood decreased with the increase in dose of ANIT and with the passage of time after the ANIT administration. Changes of the blood clearance of 99mTc-P after ANIT treatment in rats may be influenced by the disorder in the hepatocytes rather than in the bile ductule cells. The blood clearance test of 99mTc-P in rats showed a sensitive reaction for the acute hepatic dysfunction induced by ANIT equally to the serum transaminase test, the serum bilirubin test or the histological test of the liver.

Chronic toxicity tests of sodium thiocyanate with sodium nitrite in F344 rats

Sodium thiocyanate, a common environmental chemical, was found to increase the incidence of liver tumors in a group of rats treated with 0.08% in drinking water. To test the possibility that thiocyanate was catalyzing the formation of carcinogenic nitrosamines from amines and nitrite in the food, a group of 20 male and 20 female rats was given a higher dose of sodium thiocyanate (0.32%) together with sodium nitrite (0.2%) in drinking water. Similar groups of rats were given 0.32% sodium thiocyanate or 0.2% sodium nitrite in drinking water or were untreated. All treatments lasted most of the lifetime of the rats, at least 2 years. There was no difference between the groups, treated or untreated, in survival, or in the incidence of any tumor that could be related to the treatment. The results indicate that sodium thiocyanate is without carcinogenic activity in rats, alone or combined with sodium nitrite.

Early changes in bile duct lining cells and hepatocytes in rats treated with alpha-naphthylisothiocyanate

Morphological changes in bile duct lining cells precede morphological changes in hepatocytes in rats treated with 300 mg/kg body wt of alpha-naphthylisothiocyanate (ANIT). Four hours after dosing, electron microscopy showed dilation of bile ducts, loss of microvilli from bile duct epithelial cells, and an apparent opening of the tight junctions between some bile duct epithelial cells. These changes were more pronounced after 6 hr and there was in some bile duct lining cells detachment of the nuclear membrane and vacuolation of the endoplasmic reticulum. Light microscopy 6 hr after treatment with ANIT showed some portal edema and loss of gamma-glutamyl transpeptidase activity from the bile duct lining cells. By 8 hr after treatment many ducts showed clear-cut damage, with bile plugs forming and cells exfoliating into the ducts. Twenty-four hours after treatment the majority of bile ducts were destroyed but by 48 hr there was some evidence of regeneration. No tissue changes were seen at the light microscopy level in the liver parenchymal cells 4, 6, or 8 hr after treatment. At the ultrastructural level some alterations in the tight junctions between hepatocytes were seen 6 hr after treatment. No other changes were observed before this time point. By 24 hr after treatment there was focal necrosis in the parenchyma. Assay of gamma-glutamyl transpeptidase and albumin in bile gave results consistent with the histochemical evidence for the loss of activity from bile duct lining cells and for weakening of the tight junctions between hepatocytes.

Short-term toxicity study of allyl isothiocyanate in rats

Allyl isothiocyanate (AITC) was given in doses of 0, 10, 20, or 40 mg/kg (5 days/week) by oral intubation to male rats for up to 6 weeks. The highest dosage level caused a decrease in body weight, thymus weight, blood glucose and serum globulin levels. Haematological examination revealed an increased percentage of neutrophils and a decreased percentage of lymphocytes after treatment for 2 weeks. Increased liver and adrenal weights were found in all test groups. Renal dysfunction was indicated by increased urinary aspartate amino-transferase activity, reduced urine volume and changes in the specific gravity of the urine. Histopathological changes were observed in the kidneys of animals at dosages of 20 and 40 mg/kg and in the livers of animals at the highest dosage level.

Neoplastic transformation of Chinese hamster cells in vitro after treatment with flavoring agents

Chinese hamster B241 cells were treated with 5 nM allylisothiocyanate (AI) or 10 nM trans-cinnamaldehyde (CA) and surviving cells were cultivated for generations until the cells acquired the characteristics of transformed cells based on in vitro criteria: increase in (a) saturation density in monolayer culture, (b) plating efficiency at low serum level and (c) colony forming efficiency (CFE) in soft agar medium. When the values of CFE of the treated cells had become significantly high, anchorage-independent colonies were isolated, propagated and then subjected to an assay for neoplastic transformation. The anchorage-independent clonal cells (CH-AI-AG+-1 and CH-CA-AG+-2) were subcutaneously injected into a suprascapular site in nude mice. The mice were maintained in an SPF animal care facility and observed for tumor formation. Growth of neoplasm at the injection sites was observed in 6 out of 7 mice and in all of the 6 mice injected with CA- and AI-transformed cells, respectively, during 3 to 8 months after the injection, as compared with 1 out of 6 mice injected with untreated control cells. Subsequent transplantation of the tumor cells into new mice induced tumor production at the injection site in all the animals within a considerably shorter period of time than that following the initial inoculation. Malignancy of the neoplastic cells was ascertained by histological examination, and the cells were found to have karyotypes of the hamster cells after in vitro cultivation of the tumor cells. These experimental results suggest the transforming potency of the flavoring agents in Chinese hamster cells.

Ultrastructural changes in the respiratory tract of rats following methyl isocyanate inhalation

The static exposure of rats to 0.25 mg/l methyl isocyanate for 1 h resulted in damage to the epithelium of the proximal bronchioles and upper airways. Bronchiolar cells exhibited both nuclear and cytoplasmic damage; many epithelial cells, particularly in the bronchi and trachea, were killed and/or dislodged from the basement membrane. A "raft" of cell debris and fibrin lined most of the airways during the 1st week after exposure but repair to the underlying epithelium was well advanced within 2-3 days. The majority of airways were lined by a normal epithelium within 3 weeks of exposure, but isolated foci of hyperplasia and occluded airways probably accounted for continued respiratory impairment.

Methyl isocyanate subchronic vapor inhalation studies with Fischer 344 rats

Groups of Fischer 344 rats were exposed to 3.1, 0.6, 0.15, or 0.0 (control) ppm of methyl isocyanate (MIC) vapor 6 hr per day for two 4-day sessions separated by a 2-day rest. There were no deaths during the study. The rats were killed the morning following the last exposure day. The 3.1-ppm-exposed rats had decreased body weight, food consumption, and blood oxygen saturation (males only). Increased hemoglobin concentration (males only) and lung weights were also observed in this group of rats. Multiple histologic lesions, limited to the respiratory tract, were observed in rats of the 3.1-ppm group only. The lesions consisted of necrosis, suppurative inflammation, squamous metaplasia, and intraluminal and submucosal fibroplasia (bronchi and bronchioles only) which extended from the anterior nasal cavity to the terminal bronchioles. In a second study, rats were exposed to 3.0 ppm MIC, 6 hr per day, for either one or two 4-day sessions and sacrificed on postexposure Days 1, 15, 43, and 85. All rats survived the 4- or 8-day exposure regimen, although significant decreases in body weight and encrustation of the eyes, nose, or mouth area were observed. During the first 15 days postexposure, male mortality was 63%; only 6% of the MIC-exposed females died. The cause of death was interpreted to be a combination of pulmonary vascular and inflammatory changes coupled with anorexia. For survivors, recovery from the necrotizing and irritating effects of MIC vapor was observed. Squamous metaplasia of respiratory epithelium, observed in rats sacrificed at the end of the exposure period, was replaced by tall pseudostratified columnar (regenerative) epithelium beginning in the bronchi and bronchioles as well as the distal trachea. Collagen maturation and condensation of the intraluminal and submucosal fibroplasia occurred during the postexposure period. The results of these investigations support the current threshold limit value for MIC of 0.02 ppm.

Cytomorphological changes in liver cells exposed to allyl and benzyl isothiocyanate and their cysteine and glutathione conjugates

Since allyl isothiocyanate has been reported to be a bladder carcinogen and benzyl isothiocyanate is a known anti-carcinogen, it is important to know the mode of their cytotoxic action. This was investigated in a RL-4 hepatocyte cell line by studying the morphological effects of increasing concentrations of the isothiocyanates and their glutathione and cysteine conjugates. These effects were compared with those induced by tert-butylhydroperoxide which supposedly has its primary effect upon the cytosolic glutathione status and thus upon the integrity of Ca2+-sequestrating mitochondria. The results agree with the previously postulated role of conjugation in the exposure of cells to isothiocyanates: Conjugates show effects similar to those produced by the free parent compounds because conjugates release free isothiocyanates in aqueous solution. The cytomorphological effects increase in a more or less dose-dependent manner with increasing concentrations of isothiocyanate or exposure time. Probably due to increased exposure, suspended RL-4 cells are more sensitive to the toxic action than cells growing on a substrate. No qualitative differences were found between the effects of allyl and benzyl isothiocyanate, indicating that their different effects in vivo are perhaps related to organ-specific differences in equilibrium between the conjugated and unconjugated forms of the test substances. The first cytomorphological effects of isothiocyanates consist of surface blebbing (zeiosis) and swelling of dictyosomal cisternae. At higher concentrations swelling extends to vesicles of endoplasmic reticulum. Mitochondria are not affected until the cells reach the necrotic phase of injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepato-biliary transport of amaranth by single pass liver perfusion in normal and carbon tetrachloride or alpha-naphthylisothiocyanate treated rats

Hepato-biliary transport of amaranth (AM) in normal and carbon tetrachloride (CCl4) or alpha-naphthylisothiocyanate (ANIT) treated rats was studied using single pass liver perfusion. CCl4-intoxicated rats were prepared by two different methods. One was a subcutaneous injection (CCl4s.c.) and the other was an oral administration (CCl4p.o.). Though AM had been recognized to be non-metabolized in the liver, AM has been reported to be metabolized via azo-reduction by intestinal microflora and/or in the liver to yield naphthionic acid (1-amino-4-naphthalene sulfonic acid) (NSA) after oral administration. In the present investigation, AM was metabolized also in the perfused rat liver to yield NSA, which was not excreted in the bile, but effluxed into the effluent. The hepatic clearance of AM was significantly decreased in all intoxicated livers compared with the untreated livers. The concentration of NSA effluxed in the effluent was decreased in CCl4s.c.-intoxicated livers. However, in other intoxicated livers, there was no significant difference from the untreated livers in the concentration of NSA in the effluent. The amount of AM excreted in the bile was significantly decreased in CCl4s.c.- or CCL4p.o.-intoxicated livers. In ANIT-intoxicated livers, no bile excretion was observed because of the biliary stagniation. From the results of pharmacokinetic analysis using a five-compartment model, the metabolism was not altered by all treatments investigated in the present study. Subcutaneous administration of CCl4, which caused a mild intoxication, affected only the permeability of the plasma membrane of the liver to AM, but oral administration of CCl4, which caused a severe intoxication, decreased the biliary excretion of AM as well as increased the permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Histological demonstration of wheat germ lectin binding sites in the liver of normal and ANIT treated rats

Wheat-germ lectin peroxidase conjugate was used to stain the liver of normal rats and rats given alpha-naphthylisothiocyanate (ANIT). Changes in patterns in bile duct and canalicular staining were compatible with the hypothesis that cell damage caused by ANIT is essentially restricted to bile ducts.

Changes in polyamine metabolism in rat liver after oral administration of alpha-naphthylisothiocyanate

Changes in the levels of urea cycle enzymes and polyamine metabolism in the liver of rats treated with alpha-naphthylisothiocyanate (ANIT), an inducer of experimental cholestasis, were studied. Activities of arginase increased approximately two-fold compared to the control values during the period of 24-72 hours after oral administration of ANIT (100 mg/kg), while activities of ornithine carbamyltransferase and ornithine aminotransferase decreased. The activity of ornithine decarboxylase was elevated by approximately 20- and 10-fold at 12 and 60 hours, respectively, after ANIT administration. Putrescine concentration doubled 24-48 hours after the ANIT administration, but spermidine level rose more slowly and reached the level of 1.5-fold of the control level in 36-72 hours. Spermine concentration decreased initially but increased in 96 hours. These results suggest that the increased activity of urea cycle accounts for the increase in the ornithine content and that the putrescine and spermidine acts as the initiator of recovery of the liver damaged by ANIT treatment.

Evaluating toxin-induced hepatic injury in rats by laboratory results and discriminant analysis

The ability of 14 serum biochemical assays to predict the presence of hepatic necrosis induced by carbon tetrachloride (CCl4) (centrilobular necrosis), allyl alcohol (periportal necrosis), and 1-napththylisothiocyanate (ANIT) (biliary duct necrosis) was evaluated in rats. Results of these assays were analyzed using multivariate discriminant analysis to determine: which assays have the highest predictive value for discriminating between control and treated rats, and which assays would discriminate between rats in the three treatment groups. Individual assays with the highest predictive value for CCl4-induced lesions versus controls were glutamate dehydrogenase (GDH), sorbitol dehydrogenase (SDH), and alanine aminotransferase (ALT). Assays with the highest predictive value for ANIT-induced lesions were GDH, 5'-nucleotidase (5'NT), and ALT. Assays the highest predictive value for ANIT-induced lesions were GDH, 5'-nucleotidase (5'NT), and ALT. Assays with the highest predictive value for allyl alcohol-induced lesions were an ALT/isocitrate dehydrogenase (ICD) ratio, GDH, and ALT. Canonical correlation coefficients for each assay ranged from 0.98 to 0.91 with 95-100% correct group membership predictions (treated versus control) provided by each assay. Individual assays were not highly predictive for determining group membership among all three treatment groups. A two assay combination of 5'NT and an ALT/ICD ratio provided 100% correct group membership predictions and had high canonical correlations (f1 = 0.95, f2 = 0.83).

Glutathione- and cysteine-mediated cytotoxicity of allyl and benzyl isothiocyanate

Ally isothiocyanate has been reported to be a bladder carcinogen in male rats. On the other hand, benzyl isothiocyanate is an anti-carcinogen. These contradicting properties led us to investigate the cytotoxicity of these compounds in RL-4 rat hepatocytes. Since conjugation with glutathione plays an important role in the metabolism of these isothiocyanates, the glutathione and L-cysteine derivatives were also tested for cytotoxicity (electron microscopy, trypan blue exclusion, cell attachment, and inhibition of cell division). Both types of conjugates caused considerable toxicity: allyl isothiocyanate conjugates gave effects comparable to the parent compound, but benzyl isothiocyanate was more toxic than its conjugates. Addition of excess glutathione (greater than 4mM) to the free isothiocyanates as well as their conjugates abolished cytotoxicity up to the highest concentration tested (250 microM). Addition of excess L-cysteine (5 to 20 mM) lowered the effects but did not abolish them. The reaction of thiols with isothiocyanates was readily reversible: 15 min after dissolving the conjugates in buffer, pH 7.4, an equilibrium was established in which 9 to 15% of the conjugates was converted to free isothiocyanate. Two hours after addition of 1 mM of the L-cysteine conjugates to medium containing 5 mM glutathione, 80% of the total conjugates was present as the glutathione derivatives. The glutathione conjugates were similarly converted to L-cysteine conjugates. Glutathione conjugates are not able to enter the cell, thus their toxicity is presumably due to the release of free isothiocyanate, and in the presence of excess glutathione no toxicity was observed. L-cysteine derivatives are able to cross the cell membrane, thus excess L-cysteine diminishes cytotoxicity, since less free isothiocyanate is present outside the cells, but does not completely protect the cells. Glutathione and cysteine can be regarded as transporting agents for the isothiocyanates through the body. Initial detoxification can be followed by release of the reactive compound at some other site.

S-adenosyl-L-methionine protection against alpha-naphthylisothiocyanate-induced cholestasis in the rat

The effect of S-adenosyl-L-methionine (SAMe) on cholestasis induced by alpha-naphthylisothiocyanate (ANIT) was studied in rats. SAMe significantly attenuated both bile flow impairment and elevated values of serum bilirubin, glutamic pyruvic transaminase and alkaline phosphatase in ANIT-treated animals. These results suggest that SAMe protects the rat liver against the toxic effects of ANIT.

Cellular effects of endotoxin in vitro: mobility of endotoxin in the plasma membrane of hepatocytes and neuroblastoma cells

Lipopolysaccharide labeled with fluorescein isothiocyanate (FITC-LPS) was used to examine interactions between endotoxin and plasma membrane in isolated rat hepatocytes and mouse neuroblastoma NB41A3 cells. At the same endotoxin to cell ratio, hepatocytes bound more toxin than did neuroblastoma cells. At a dose of 12 micrograms/mg dry wt, a bound mobile fraction of between 60 and 75% of FITC-LPS was found on hepatocytes at 25 degrees C with a lateral diffusion coefficient (D) of 4.0 X 10(-9) cm2/s. In neuroblastoma cells, the mobile fraction was larger (85-90%), with D 1.0 X 10(-8) cm2/s. D was temperature-dependent between 10 and 37 degrees C and increased from 1.8 X 10(-9) to 1.0 X 10(-8) cm2/s in hepatocytes and from 9.4 X 10(-9) to 1.9 X 10(-8) cm2/s in neuroblastoma cells. In both types of cell, nonviable (cells which did not exclude Trypan blue) as compared to viable cells showed different recovery patterns and 100% of the probe molecules were mobile. These results suggest that: (1) endotoxin binding to mammalian cells consists of two subpopulations with different mobilities; (2) binding of the immobile fraction is dependent on cellular integrity; and (3) the differences in binding, lateral mobility, and size of the immobile fraction in hepatocytes and neuroblastoma cells may be due to variations in membrane composition and/or number of binding sites.

Four-week toxicity study of phenyl isothiocyanate in rats

In a subacute toxicity study, phenyl isothiocyanate (PIT) was administered to male rats on 5 days/wk by gastric intubation at dose levels of 0, 2.5, 10 and 40 mg/kg body weight/day for 4 wk. Body-weight gain was recorded weekly and a complete haematological examination and determinations of alanine aminotransferase, aspartate aminotransferase and thyroxine in serum were performed. The heart, liver, spleen, kidneys, thyroid, adrenals and mesenteric lymph nodes were weighed and examined microscopically. In the highest dose group, slightly decreased growth and a statistically significant increase in mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration were noted. Relative heart, liver, kidney and adrenal weights also showed a statistically significant increase in the highest dose group. Total serum thyroxine and free thyroxine were decreased in the groups given 10 or 40 mg PIT/kg. Microscopic examinations revealed no abnormalities. The measurement of the serum thyroxine concentration appeared to be the most sensitive indicator of an effect in this experiment.

[Safety of animal husbandry products produced by using allyl isothiocyanate-preserved feeds]

To examine the safety of foods (meat and milk) obtained from animals whose feeds were preserved with allyl isothiocyanate (AITC), the authors investigated the status and development of animals, some aspects of protein, lipid and carbohydrate metabolism, some enzymes, hemopoiesis and reproduction function of Wistar rats fed diets containing the above products (55 g dry milk or 50 g boiled meat per 100 g diet). To measure the residual quantity of allylamine (AA), the main metabolite of AITC, a chromato-fluorometric method with the use of dansyl chloride was devised, permitting the detection of 2 ng AA in the spot. The relative standard deviation was 0.14-17. The degree of AA extraction amounted to 96%. The method made it possible to detect the residual quantity of AA in the kidneys (up to 12.2 +/- 2.0 micrograms/kg) and in the liver (up to 83.1 +/- 12.4 micrograms/kg). The data obtained evidence that AA cannot be used as conservant for manufacturing feeds for agricultural animals.

Effect of thiocyanate levels in milk on thyroid function in iodine deficient subjects

To utilize the antibacterial effect of the lactoperoxidase system to prevent bacterial spoilage of raw milk it is necessary to increase the thiocyanate concentration of the milk. Thiocyanate has, however, a potent antithyroid effect which is enhanced by iodine deficiency. In this study the thyroid function has been studied, before and after 4 weeks daily administration of 250 ml of such treated milk, in 55 goitrous subjects living in an endemic goiter region of western Sudan. The iodine content was 0.1 mg/l and the thiocyanate content was either 3.6 mg/l (n 19) or 19 mg/l (n 36) in the milk. At the start of the experiment all subjects were iodine deficient with a urinary excretion of 40-50 micrograms/g creatinine. After 4 weeks daily intake of 4.75 mg of thiocyanate by way of milk the serum thiocyanate level increased by approximately 1.7 mg/l. Both at the beginning and at the end of the experimental period the serum levels of thyroxine, triiodothyronine and TSH were in the normal range for all subjects. After 4 weeks the TSH levels had decreased significantly, (from 2.6 +/- 0.2 to 2.1 +/- 0.2 mU/l, p less than 0.001) probably as an effect of the supplementary intake of iodine. The thyroid hormone levels remained unchanged during the experimental period. In conclusion, the intake of milk with an iodine concentration of 0.1 mg/l and a thiocyanate concentration of 19 mg/l does not have a negative effect on the thyroid function in iodine deficient subjects.

Allyl isothiocyanate is mutagenic in Salmonella typhimurium

Allyl isothiocyanate, a naturally occurring compound, component of oil of mustard and human food plants such as cabbage, cauliflower and horseradish, has up to now been regarded as nonmutagenic in bacterial mutagenicity testing systems. Recently, however, it was found to cause transitional-cell papillomas in the urinary bladder of male F344 rats. Contrary to earlier reports, in this study allyl isothiocyanate showed clear mutagenicity for Salmonella typhimurium TA100 in the preincubation assay after longer, non-standard preincubation times (greater than 20 min). The mutagenicity is expressed only in the presence of a rat-liver homogenate metabolising system, i.e. it is indirect. However, high concentrations of rat-liver homogenate suppress the mutagenicity of allyl isothiocyanate. SKF525, inhibitor of microsomal oxygenase, reduces the mutagenic potential which on the other hand is increased in the presence of 1,1,1-trichloropropene-2-oxide, inhibitor of epoxide hydrolase. This indicates the occurrence of an epoxide intermediate in allyl isothiocyanate metabolism. Another metabolic pathway, namely hydrolysis to allyl alcohol and oxidation to acrolein, a known mutagen, also seems possible as cyanamide, inhibitor of aldehyde dehydrogenase, can slightly increase the mutagenic potential. The reason(s) for allyl isothiocyanate's requirement for long preincubation times to express mutagenicity still requires elucidation, and the question arises: is allyl isothiocyanate a single, exceptional case or not?

Allyl isothiocyanate: comparative disposition in rats and mice

Allyl isothiocyanate (AITC), the major component of volatile oil of mustard, was recently reported to induce transitional-cell papillomas in the urinary bladder of male Fischer 344 rats, but not in the bladders of female rats or B6C3F1 mice. The present investigation of comparative disposition in both sexes of each species was designed to detect sex or species differences in disposition which might explain susceptibility to AITC toxicity. AITC was readily cleared from all rat and mouse tissues so that within 24 hr after administration less than 5% of the total dose was retained in tissues. The highest concentration of AITC-derived radioactivity was observed in male rat bladder. Clearance of AITC-derived radioactivity by each species was primarily in urine (70 to 80%) and in exhaled air (13 to 15%) with lesser amounts in feces (3 to 5%). Rats excreted one major and four minor metabolites in urine. The major metabolite from rat urine was identified by NMR spectroscopy to be the mercapturic acid N-acetyl-S-(N-allylthiocarbamoyl)-L-cysteine. Mice excreted in urine the same major metabolite identified in rat urine as well as three other major and two minor metabolites. Sex-related variations were observed in the relative amounts of these metabolites. Both species excreted a single metabolite in feces. Metabolism of AITC by male and female rats was similar, but female rats excreted over twice the urine volume of male rats. Results of the present study indicate that excretion of a more concentrated solution of AITC metabolite(s) in urine may account for the toxic effects of AITC on the bladder of male rats.