Pathologic and biochemical effects of azaserine in inbred Wistar/Lewis rats and noninbred CD-1 mice.

Inbred W/LEW rats and noninbred CD-1 mice were compared for responsiveness to induction of pancreatic adenocarcinomas by azaserine. At 1 year following the first of 15 weekly ip injections of 10 mg azaserine/kg body weight, the rats had a pancreatic adenoma incidence of 71% (12/17) and a pancreatic adenocarcinoma incidence of 35% (6/17), with 1 invasive adenocarcinoma. The mice showed none of these advanced lesions, although numerous pancreatic atypical acinar cell nodules (AACN) were present. An examination of the number and size of the AACN showed the rats to hve more and larger AACN thatn did the mice. The concentration of [14C]azaserine and/or its metabolites was greater in rat pancreas than in mouse pancreas. Alkaline sucrose gradients were used to compare azaserine-induced pancrewtic and liver DNA damage in W/LEW and F344 rats, the CD-1 mouse, the Syrian golden hamster, and the strain 13 guinea pig. DNA damage was detected 1 hour following azaserine administration in both pancreata and livers of all animals tested and persisted for at least 1 week in the pancreata of all animals except the CD-1 mouse; however, neither the degree nor persistence of DNA damage accurately reflected the differing responsiveness of these species to induction of pancreatic AACN or neoplasms by azaserine.

Neoplastic response of F344 rats and B6C3F1 mice to the polymer and dyestuff intermediates 4,4'-methylenebis(N,N-dimethyl)-benzenamine, 4,4'-oxydianiline, and 4,4'-methylenedianiline.

Feeding 4,4'-methylenebis(N,N-dimethyl)benzenamine [CAS: 101-61-1; 4,4'-methylenebis(N,N-dimethylaniline)] to inbred F344 rats increased the incidence of thyroid lesions (hyperplasia, adenomas, and carcinomas) in both sexes, especially in the female rats. 4,4'- Oxydianiline (CAS: 101-80-4) in the diet increased adenomas and carcinomas in the thyroid gland and neoplastic nodules and carcinomas in the liver of male and female F344 rats. In addition to increasing thyroid adenomas in females and hepatocellular adenomas or carcinomas in male and female B6C3F1 mice, 4,4'- oxydianiline increased adenomas of the harderian gland in male and female mice. 4,4'- Methylenedianiline (CAS: 101-77-9) in the drinking water increased neoplasms of the thyroid gland and liver in F344 rats and B6C3F1 mice.

Effect of age on nodule induction by azaserine and DNA synthesis in rat pancreas.

The efficacy of various azaserine treatment durations was evaluated with respect to induction of atypical acinar cell nodules in Wistar rat pancreas and was related to animal age and rate of pancreatic DNA synthesis during growth. The sensitivity to nodule induction was maximal in postnatal rats when the rate of pancreatic DNA synthesis was high, whereas treatment of weanlings was less effective and treatment of mature rats was least effective. When weaned growing rats were given 1, 3, or 5 weekly injections of 30 mg azaserine/kg, the number of nodules induced was proportional to the number of injections. A single dose at this level did not induce detectable pancreatic necrosis or inflammation; therefore, DNA synthesis due to regeneration was probably not a major factor in the initiation of nodules. We concluded that multiple daily injections of [3H]thymidine during the first or second postnatal week provided DNA of sufficiently high specific activity for use in DNA repair and biochemical toxicity studies.

Bromodichloromethane, a trihalomethane that produces neoplasms in rodents.

Bromodichloromethane, a trihalomethane found in water supplies after chlorination, was administered by gavage in corn oil to male and female F344/N rats and B6C3F1 mice for up to 2 years at dose levels of 0, 50, or 100 mg/kg to rats, 0, 25, or 50 mg/kg to male mice, and 0, 75, or 150 mg/kg to female mice. Survival at 2 years in rats and in male mice was comparable among groups and was greater than 50% at the termination of the experiment. Survival in female mice was greater than 50% in all groups until week 84 but was reduced toward the end of the study because of ovarian abscesses in some female mice. There was clear evidence of carcinogenicity in males and females of both species as shown by increased incidences of tubular cell adenomas and adenocarcinomas in the kidney and adenocarcinomas and adenomatous polyps in the large intestine in male and female rats, increased incidences of tubular cell adenomas and adenocarcinomas in the kidney of male mice, and increased incidences of hepatocellular adenomas and carcinomas in female mice. Of the three trihalomethanes studied to date in the National Cancer Institute/National Toxicology Program (chloroform, chlorodibromomethane, or bromodichloromethane) bromodichloromethane caused the widest spectrum of neoplasms in rodents.

Transplantation of azaserine-induced carcinomas of pancreas in rats.

Two pancreatic adenocarcinomas which had been induced in Wistar/Lewis rats by azaserine treatment were transplanted into rats of the same strain by subcutaneous and intraperitoneal injection of minced tumor. Subsequently, we have serially transplanted into non-radiated recipients. Transplanted tumors have maintained evidence of acinar cell differentiation including the presence of zymogen granules in tumors studied by electron microscopy, and of lipase, amylase and trypsin activity in the supernatant of tumor homogenates. Histologically, the tumors vary from poorly differentiated solid carcinomas to well differentiated variants which form acini. Transplanted tumors are locally invasive and have metastasized to lung and liver in some recipients.

Response of the Syrian golden hamster to a nitrosourea amino acid carcinogen.

Syrian golden hamsters were treated with N delta-(N-methyl-N-nitrosocarbamoyl)-L-ornithine (MNCO), a nitrosourea amino acid, which has induced a high incidence of breast, kidney and skin neoplasms and a low incidence of pancreatic carcinoma in rats. MNCO induced a few breast and skin carcinomas, and a high incidence of foci of atypical acinar cells and of focal ductular abnormalities in the exocrine pancreas. The latter were similar to lesions observed in rats treated with MNCO. MNCO was less toxic and less effective as a carcinogen in hamster than in the rat.

Studies of DNA damage in rat pancreas and liver by 6-diazo-5-oxo-L-norleucine, ethyl diazoacetate and azaserine.

One hour following intraperitoneal injection of the pancreatic and liver carcinogen azaserine, 10 mg/kg (0.06 mmol/kg), DNA damage is present in both pancreas and liver of Wistar/Lewis rats as determined with alkaline sucrose gradients. Single injections (0.06 mmol/kg) of either of 2 structural analogues of azaserine, 6-diazo-5-oxo-L-norleucine (DON) and ethyl diazoacetate (EDA), do not damage pancreatic or liver DNA. EDA administered at 0.5 mmol/kg damages liver DNA, but not pancreatic DNA. Total radioactivity in pancreas and liver of Wistar rats 1 h after intravenous injection of [14C]azaserine, (10 microCi/kg), is 2.8 and 1.3 times respectively, the level of 14C-activity in pancreas and liver following injection [14C]EDA. Three to four times as much [14C]EDA localizes in the liver of Wistar rats as in the pancreas. Azaserine (0.06 mmol/kg weekly for 6 weeks) induces atypical acinar cell nodules (AACN) in pancreas of Wistar/Lewis rats. DON (0.06 mmol/kg weekly for 6 weeks) induces an elevated incidence, but low number of AACN in pancreas. EDA (0.10 mmol/kg weekly for 6 weeks) does not induce pancreatic AACN.

Comparative toxicity of ethylene dichloride in F344/N, Sprague-Dawley and Osborne-Mendel rats.

Studies were conducted to compare the toxicity of ethylene dichloride (EDC) in F344/N rats, Sprague-Dawley rats, and Osborne-Mendel rats. Ten rats/sex/group were exposed to EDC in drinking-water at 0, 500, 1000, 2000, 4000 and 8000 ppm for 13 wk. The highest concentration was limited by the maximum solubility of EDC in water (about 9000 ppm). In addition, F344/N rats (10/sex/group) were administered EDC in corn oil by gavage to compare toxicity resulting from bolus administration with that of continuous exposure in drinking-water. Gavage doses of EDC were within the range of total daily doses (in mg/kg body weight/day) resulting from exposure in drinking-water. EDC administered by gavage resulted in greater toxicity to F344/N rats than did administration of similar doses in drinking-water. All males receiving 240 and 480 mg/kg body weight and 9/10 females receiving 300 mg/kg body weight by gavage died before the end of the study. Necrosis of the cerebellum was observed in the brains of 3 males receiving 240 mg/kg body weight and 3 females receiving 300 mg/kg body weight. Hyperplasia and inflammation of the forestomach mucosa were observed in 8 male and 3 female rats that died or were killed in moribund condition. EDC caused minimal toxicity to F344/N, Sprague-Dawley and Osborne-Mendel rats at the drinking-water concentrations used in these studies; only female F344/N rats had EDC-related renal lesions. Based on mortality and EDC-related lesions, the no-effect levels for EDC administered by gavage to F344/N rats were 120 mg/kg body weight for males and 150 mg/kg body weight for females.

Chronic effects of agar, guar gum, gum arabic, locust-bean gum, or tara gum in F344 rats and B6C3F1 mice.

Diets containing 25,000 (2.5%) or 50,000 ppm (5.0%) agar, guar gum, gum arabic, locust-bean gum or tara gum were fed to groups of 50 male and 50 female F344 rats and B6C3F1 mice for 103 wk. Separate groups of 50 rats and 50 mice of each sex served as controls for each study. There were no significant differences in survival between any of the dosed groups of rats or mice and their respective control groups. Depressions in body-weight gain greater than 10% for dosed groups relative to their respective control groups were observed for male (low dose only) and female mice fed diets containing agar, female mice fed diets containing guar gum (high dose only), male mice fed diets containing locust-bean gum (high dose only) and male and female mice fed diets containing tara gum (high dose only). Depressions in body-weight gain greater than 5% were observed for female rats fed diets containing agar, guar gum or gum arabic. There were no histopathological effects associated with the administration of the test materials. Under the conditions of these bioassays, none of the five polysaccharides was carcinogenic for F344 rats or B6C3F1 mice of either sex.

Pancreatic carcinoma in azaserine-treated rats: induction, classification and dietary modulation of incidence.

Pancreatic carcinomas have been induced in Wistar and W/LEW rats by administration of total azaserine doses of 150-520 mg/kg by injection or oral routes over periods of 5-52 weeks. The latent period for development of invasive carcinomas was 1-2 years, but focal abnormalities in acinar cells appear earlier. The incidence of carcinomas varied with total dose, route, and schedule of azaserine administration. The spectrum of histologic patterns of the carcinomas included well and poorly differentiated acinar cell, ductlike, and undifferentiated carcinomas. Rats fed a purified diet developed more pancreatic neoplasms than rats fed a commercial laboratory chow. Selective feeding of these diets during the administration of carcinogen and following completion of carcinogen treatment indicated that the inhibitory effect of chow on pancreatic carcinogenesis was exerted during the postinitiation phas. Supplementation of diet with 0.025% retinyl acetate during the postinitiation phase also inhibited the progression of azaserine-induced lesions in the pancreas.

Thirteen-week toxicology studies of 1-amino-2,4-dibromoanthraquinone in Fischer 344/N rats and B6C3F1 mice.

1-Amino-2,4-dibromoanthraquinone (ADBAQ), an intermediate in the production of commercial dyes for wool, silk, and synthetic fibers, was selected for toxicology and carcinogenesis studies in two rodent species. In advance of the 2-year studies, 13-week studies were conducted in male and female F344/N rats and B6C3F1 mice which were fed a diet containing ADBAQ at concentrations of 0, 0.25, 0.50, 1.00, 2.50, and 5.00%. ADBAQ stained the skin and fur red at all doses in rats and at 1.00% and higher concentrations in mice. Lethargy and emaciation were noted at the 2.50% and higher doses in rats of both sexes. In general, the absolute weight of the liver and the liver/organ weight ratios increased in both sexes and species at all doses. Treated rats developed a chronic toxic hepatitis characterized by hepatocytomegaly, centrilobular vacuolar degeneration and necrosis, regenerative nodules, acute necrotizing cholangitis, bile duct hyperplasia, chronic active inflammation in periportal areas, and focal pigmentation. The hepatopathy occurred at all doses in males and at 0.50% and higher in females and correlated with elevations of serum glutamic-pyruvic and glutamic-oxaloacetic transaminases, leukocytosis, and neutrophilia. Hyaline droplet degeneration in the proximal convoluted tubules of the kidneys occurred in male rats, and uterine atrophy was observed in female rats at 1.00% and higher. Anemia occurred in both sexes of rats at all doses and thymic atrophy was observed in both sexes of high-dose rats. In male mice minimal dose-related lesions in the liver included centrilobular glycogen depletion at 1.00% and higher and pigmentation at all doses. At comparable doses, ADBAQ was considered to be markedly toxic in rats and of minimal nonlife-threatening toxicity in mice.

Toxicity and carcinogenicity of chlorodibromomethane in Fischer 344/N rats and B6C3F1 mice.

Chlorodibromomethane, a trihalomethane found in water supplies after chlorination, was administered by gavage in corn oil to male and female Fischer 344/N rats and B6C3F1 mice in toxicity studies of 13 weeks and 2 years duration. Doses used in the 13-week study were 0, 15, 30, 60, 125, and 250 mg/kg in rats and mice. At 250 mg/kg, hepatic and renal toxicity was produced in male and female rats and male mice, and mortality was increased in male and female rats. In the chronic study, male and female rats were administered the chemical at 0, 40, and 80 mg/kg. No adverse effects on survival in treated rats were observed. Male rats receiving 80 mg/kg had reduced body weight gains relative to controls. Fatty change and cytoplasmic changes were seen in the liver of treated male and female rats. The male and female mice in the chronic study received doses of 0, 50, and 100 mg/kg of chemical. A dosing accident rendered the number of low-dose male mice inadequate for statistical analysis. High-dose male mice had reduced survival relative to controls. Survival was similar in dosed and control female mice. Dosed male and high-dose female mice had reduced body weight relative to controls. Non-neoplastic hepatic lesions were seen in treated male mice (necrosis and hepatocytomegaly) and in treated female mice (calcification and fatty change); nephrosis was seen in treated male mice. The incidence of hepatocellular adenoma and carcinoma (combined) was increased in treated female mice, but only marginally so in treated male mice. Chlorodibromomethane, like chloroform, is toxic to liver and kidneys, and like chloroform induces hepatocellular tumors in mice.

Carcinogenicity in rats of the nitrosourea amino acid N delta-(N-methyl-N-nitrosocarbamoyl)-L-ornithine.

The carcinogenicity of the nitrosourea amino acid, N delta-(N-methyl-N-nitrosocarbamoyl)-L-ornithine (MNCO), and its acute cytotoxicity were studied in Wistar rats. MNCO treatment induced a high incidence of neoplasms in breast, kidney, and skin and a lower incidence of tumors in the exocrine pancreas and ear duct. The duration of these studies was limited by toxicity and carcinogenicity to six months in a high dose group which received 1 mmole MNCO/kg IP weekly for 6 months and to 1 year in a group which received 0.33 mmole/kg. In the latter group the incidence of neoplasms was breast, 40%; skin, 52%; kidney, 81%; pancreas, 19%; and ear duct, 4%. All pancreases in this group also contained foci of fibrosis and cyst formation, and atypical acinar cell nodules. Acute cytotoxic effects were noted in pancreas, kidney and skin after a single IP injection of 3 mmoles/kg although this dose caused no deaths acutely.

Detection of mutagenic activity in the urine of rodents treated with p-rosaniline.

p-Rosaniline was fed to male and female Fischer 344 rats and B6C3F1 mice at doses of 1,000 and 2,000 ppm for male rats and 500 and 1,000 ppm for female rats and mice of both sexes. Urine was collected overnight at 1-wk intervals over a 4-wk treatment period and frozen until its use in the mutagenicity assay. The neat urine was tested in triplicate without S-9 on Salmonella tester strains TA98, TA100, TA1535, and TA1537 at 0.75, 0.5, 0.2, and 0.05 ml per plate. When sufficient urine was available, samples were tested on TA100 in the presence of S-9. Either urine samples were pretreated for 18 hr at 37 degrees C with beta-glucuronidase, or the deconjugating enzyme was added to the top agar at the time of plating in the mutagenicity assay (non-pretreatment). Direct-acting mutagenic activity was detected on TA98 in the urine from male mice, but only when using the non-pretreatment deconjugation method. No direct-acting mutagenic activity was detected in the urine of male and female rats and female mice; however, in the presence of S-9, mutagenic activity was observed in the urine of male rats and in the urine of male and female mice regardless of the deconjugation method used. The non-pretreatment method was superior for detecting direct acting mutagenic activity, and the pretreatment method was superior for detecting mutagenic activity requiring metabolic activation by S-9.

No evidence of toxicity or carcinogenicity of pentaerythritol tetranitrate given in the diet to F344 rats and B6C3F1 mice for up to two years.

Toxicology and carcinogenesis studies of pentaerythritol tetranitrate (PETN), an organic nitrate used in explosives and as a therapeutic agent for angina pectoris, were conducted by administering diets containing PETN,NF (National Formulary Grade, a 1:4 mixture of PETN and lactose) to both sexes of F344 rats and B6C3F1 mice in 14-day, 13-week and 2-year studies. PETN was found to be essentially non-toxic in 14-day and 13-week studies at dietary concentrations as high as 10,000 ppm; the weight gain of female rats was lower than that of controls at 5000 and 10,000 ppm in the 13-week study. In the 13-week studies, one in ten high-dose female rats had an adenoma of the Zymbal gland and one in ten high-dose female mice had a hepatocellular adenoma. Dietary concentrations chosen for the 2-year studies were 5000 and 10,000 ppm for male rats and male and female mice, and 1240 and 2500 ppm for female rats. In the 2-year studies, there were no adverse effects on survival or body weight gains in either sex of rats or mice. No neoplastic or non-neoplastic lesions were considered to be related clearly to PETN administration. Neoplasms of the Zymbal gland occurred at low incidences in PETN-exposed groups of both sexes of rats in the 2-year study.