Lack of subchronic toxicity of an aqueous extract of Agaricus blazei Murrill in F344 rats.

Agaricus blazei Murrill, an edible mushroom, is widely used as a functional food due to its possible medicinal effects. Aqueous extracts are also used as food additive to provide an agreeable bitter taste. As a part of its safety assessment, the present 90-day subchronic toxicity study was performed in F344 rats. To establish a no-observed-adverse-effect level (NOAEL), rats were fed powder diet containing A. blazei Murrill aqueous extract at dose levels of 0 (basal diet), 0.63, 1.25, 2.5 and 5% (maximum) for 90 days. During the experiment, there were no remarkable changes in general appearance and no deaths occurred in any experimental group. Although serum blood urea nitrogen was slightly but significantly increased in males of the 2.5 and 5% groups, no related histopathological changes were observed in the kidney, and serum creatinine levels were rather reduced, suggesting the increase of blood urea nitrogen to be of little toxicological significance. Hematology, organ weight measurement and histopathological observation revealed no test compound-related toxicological changes. In conclusion, A. blazei Murrill extract even at 5% in the diet (2654 mg/kgb.w./day for male rats and 2965 mg/kgb.w./day for female rats) did not cause remarkable adverse effects in F344 rats. Thus, the NOAEL was concluded to be 5% in the diet.     

A 13-week subchronic toxicity study of paprika color in F344 rats.

The fruit of the paprika (Capsicum annuum) has been widely used in various countries as a spice and food-coloring additive. As a part of the safety assessment of paprika color (Paprika oleoresin), a 13-week subchronic toxicity study was performed in F344 rats. To establish a no-observed-adverse-effect level (NOAEL) for application in subsequent long-term studies, rats were fed powder diet containing paprika color at dose levels of 0 (basal diet), 0.62, 1.25, 2.5 and 5% (maximum) for 13 weeks. During the experiment, there were no remarkable changes in general appearance and no deaths occurred in any experimental group. Although serum total cholesterol was dose-dependently increased in both sexes, no related histopathological changes were observed in the liver. Slight inflammatory cell infiltration in the myocardium and vacuolation of hepatocytes were noted in both control and paprika color-treated animals, but there were no clear differences between groups. In conclusion, paprika color even at 5% in the diet (0.67 g/rat/day or 2948.4 mg/kg bw/day for male rats and 0.43 g/rat/day or 3197.4 mg/kg bw/day for female rats) did not cause remarkable adverse effects in F344 rats. Thus, the NOAEL and the maximum dose level for carcinogenicity testing of paprika color were concluded to be 5% in the diet.     

Toxicology and carcinogenesis studies of goldenseal root powder (Hydrastis Canadensis) in F344/N rats and B6C3F1 mice (feed studies)

Goldenseal root powder is used in folk medicine for the treatment of gastrointestinal disturbances, urinary disorders, hemorrhage, skin, mouth, and eye infections, and inflammation. The major alkaloids in goldenseal are berberine, hydrastine, and canadine. Goldenseal root powder was nominated for study by the National Institute of Environmental Health Sciences based on the potential for human exposure and the lack of carcinogenicity data, and because it is one of the most widely used herbs in the United States. Male and female F344/N rats and B6C3F1 mice were exposed to ground goldenseal root powder in feed for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were fed diets containing 0, 1,560, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 155, 315, 630, 1,190, 2,465, and 4,815 mg goldenseal root powder/kg body weight for males and 150, 290, 640, 1,240, 2,370, and 4,870 mg/kg for females) for 15 days. All rats survived to the end of the study. Mean body weights and feed consumption of all exposed groups of males and females were similar to those of the control groups throughout the study. Liver weights of males exposed to 6,250 ppm or greater and females exposed to 12,500 ppm or greater were significantly greater than those of the controls. Minimal to moderate hepatocellular hypertrophy occurred in three males and all females exposed to 25,000 ppm and in all 50,000 ppm males and females. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were fed diets containing 0, 1,560, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 380, 840, 1,760, 3,435, 6,700, and 15,170 mg/kg body weight for males and 330, 670, 1,240, 2,375, 4,760, and 8,475 mg/kg for females) for 15 days. All mice survived to the end of the study. Mean body weights and feed consumption of all exposed groups of males and females were similar to those of the control groups throughout the study. Significant increases in liver weights occurred in males exposed to 25,000 and 50,000 ppm and in females exposed to 50,000 ppm. Absolute and relative thymus weights of 12,500 and 50,000 ppm males were significantly decreased. Minimal hypertrophy of centrilobular hepatocytes occurred in all males and females exposed to 50,000 ppm. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 255, 500, 1,000, 2,020, and 4,060 mg/kg for males and 260, 500, 1,030, 2,070, and 4,100 mg/kg for females) for 14 weeks. Additional groups of 10 male and 10 female clinical pathology study rats were given the same concentrations for 23 days. All rats survived to the end of the study. None of the body weights or mean body weight gains were significantly different from those of the controls. Feed consumption by exposed groups was generally similar to that by controls throughout the study. Liver weights were significantly increased in males exposed to 6,250 ppm or greater and in all exposed groups of females. The incidences of hepatocyte hypertrophy were significantly increased in the liver of males and females exposed to 12,500 ppm or greater; cytoplasmic vacuolization of hepatocytes occurred in all exposed males. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were fed diets containing 0, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 680, 1,360, 2,260, 5,370, and 10,550 mg/kg for males and 590, 1,250, 2,345, 4,790, and 10,740 mg/kg for females) for 14 weeks. All mice survived to the end of the study. Mean body weights of males exposed to 50,000 ppm and females exposed to 25,000 or 50,000 ppm were significantly less than those of the controls. Feed consumption by 3,121, 6,250, 12,500, 25,000, and 50,000 ppm males was similar to that by controls. Liver weights were significantly increased in males exposed to 12,500 ppm or greater and in females exposed to 25,000 or 50,000 ppm. The left epidydimal weight in male mice was significantly decreased relative to controls. The incidences of hepatocyte hypertrophy were significantly increased in males and females exposed to 12,500 ppm or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 3,000, 9,000, or 25,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 135, 400, and 1,175 mg/kg for males and 150, 470, and 1,340 mg/kg for females) for 105 to 106 weeks. Survival of 9,000 ppm females was significantly greater than that of the controls. Mean body weights of females exposed to 9,000 ppm were 6% less than those of the controls after week 37, and those of 25,000 ppm females were 6% less than those of the controls after week 8. Feed consumption by exposed groups of males and females was generally similar to that by the controls throughout the study. The incidences of hepatocellular adenoma were significantly increased in males and females exposed to 25,000 ppm, and the incidence of hepatocellular adenoma or carcinoma (combined) was significantly increased in 25,000 ppm males. All exposed groups of males and females had significantly increased incidences of hepatocyte hypertrophy. The incidences of hepatocyte degeneration were significantly increased in all exposed groups of males and in 9,000 and 25,000 ppm females. The incidences of eosinophilic focus were significantly increased in 9,000 and 25,000 ppm males and all exposed groups of females. The incidences of cardiomyopathy were significantly decreased in all exposed groups of males and in 25,000 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 3,000, 9,000, or 25,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 375, 1,120, and 3,275 mg/kg for males and 330, 1,000, and 2,875 mg/kg for females) for 105 to 106 weeks. Survival of 9,000 ppm females was significantly less than that of the controls. Mean body weights of females exposed to 25,000 ppm were 3% to 9% less than those of the controls after week 13, 6% less for weeks 14 to 52, and 5% less for weeks 53 to 101. Feed consumption by exposed groups of males and females was generally similar to that of the controls throughout the study. The incidences of hepatocellular adenoma occurred with a positive trend in males, and the incidences of multiple hepatocellular adenoma were significantly increased in 9,000 and 25,000 ppm males. The incidences of hepatoblastoma occurred with a positive trend in males with a marginal increase in the 25,000 ppm group. Significantly increased incidences of eosinophilic focus or mixed cell focus occurred in all exposed groups of males. GENETIC TOXICOLOGY: Goldenseal root powder was not mutagenic in Salmonella typhimurium or Escherichia coli tester strains, with or without liver S9 metabolic activation enzymes. In addition, no increases in the frequencies of micronucleated erythrocytes were observed in peripheral blood samples from mice exposed to goldenseal root powder in feed for 3 months. Berberine chloride was also tested for mutagenicity in standard screening assays. No mutagenicity was observed in several tester strains of Salmonella typhimurium, with or without rat or hamster liver S9 metabolic activation enzymes. In an acute exposure assay, no increase in the frequency of micronucleated polychromatic erythrocytes was seen in bone marrow of male mice administered three intraperitoneal injections of berberine chloride at 24-hour intervals. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was clear evidence of carcinogenic activity of goldenseal root powder in male F344/N rats based on the increased incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined). There was clear evidence of carcinogenic activity of goldenseal root powder in female F344/N rats based on the increased incidence of hepatocellular adenoma. There was some evidence of carcinogenic activity of goldenseal root powder in male B6C3F1 mice based on the increased incidences of hepatoblastoma and multiple hepatocellular adenoma. There was no evidence of carcinogenic activity of goldenseal root powder in female B6C3F1 mice exposed to 3,000, 9,000, or 25,000 ppm goldenseal root powder in feed for 2 years. Administration of goldenseal root powder resulted in increased incidences of nonneoplastic lesions in the liver of male and female rats and male mice.     

No evidence of carcinogenicity for L-ascorbic acid (vitamin C) in rodents

Carcinogenesis studies of L-ascorbic acid were conducted by offering diets containing 0, 25,000 or 50,000 ppm L-ascorbic acid to groups of 50 F344/N rats and 50 B6C3F1 mice of each sex for 103 wk. Survival of dosed and control female rats and of dosed and control female mice were comparable. Survival of high-dose male rats was slightly greater than that of the controls, whereas survival of high-dose male mice was significantly greater than that of the controls. There was no observed differences in neoplasms between treated and control groups that were considered related to L-ascorbic acid. In female rats, several lesions usually seen in aged animals showed a dose-related decline. Under the conditions of these studies, L-ascorbic acid given at 2.5% or 5.0% in the diet for 103 wk was not toxic or carcinogenic for male and female F344/N rats or for male and female B6C3F1 mice.     

A 90-day toxicity study of l-asparagine, a food additive, in F344 rats

L-asparagine is an amino acid listed as an existing food additive in Japan. The present 90-day toxicity study in F344/DuCrlCrj rats was conducted for safety assessment and to determine a no observed adverse effect level (NOAEL) of L-asparagine. Groups of 10 males and 10 females were given the material at dose levels of 0%, 1.25%, 2.5% or 5% in diet for 90 days. During the experiment, there were no remarkable changes in general conditions and no deaths occurred in any group. Final body weights of male 5% and 1.25% groups were significantly decreased. There were also significant increases in relative organ weights of the brain, kidney and testis in 5% males. On serological examination, GLU, PL, K and ALT were increased significantly in 5% females, and GLU was increased significantly and CRN was decreased significantly in the female 1.25% group. However, histopathological examination did not reveal any significant variation in development of lesions among the groups. Changes in body and organ weights, as well as other parameters, were concluded to be due to treatment with 5% L-asparagine. The NOAEL was determined to be 2.5% in the diet (males, 1.65 g/kg body weight/day; females, 1.73 g/kg body weight/day).     

Thirteen-week oral toxicity of 1,4-dioxane in rats and mice

Subchronic oral toxicity of 1,4-dioxane was examined by administering 1,4-dioxane in drinking water at 6 different concentrations of 0 (control), 640, 1,600, 4,000, 10,000 or 25,000 ppm (wt/wt) to F344 rats and BDF(1)mice of both sexes for 13 weeks. Food and water consumption and terminal body weight were decreased dose-dependently in rats and mice. A dose-dependent increase in the relative weights of kidney and lung was noted in rats and mice, while the relative liver weight was increased only in rats. Increases in plasma levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and a decrease in plasma glucose were noted primarily in the rats and mice dosed 25,000 ppm. Histopathological examination revealed that 1,4-dioxane affected the upper and lower respiratory tracts, liver, kidneys and brain in rats, while only the former two organs were affected in mice. Nuclear enlargement occurred in the respiratory, olfactory, tracheal and bronchial epithelia of the 1,4-dioxane-dosed rats and mice. The 1,4-dioxane-induced hepatic lesions were characterized by centrilobular swelling and necrosis in rats and mice and by glutathione S-transferase placental form (GST-P)-positive altered hepatocellular foci in rats, which are known as preneoplastic lesions. A no-observed-adverse-effect-level (NOAEL) was determined at 640 ppm for both rats and mice, since the nuclear enlargement in the nasal respiratory epithelium and the centrilobular swelling of hepatocytes in rats and the nuclear enlargement in the bronchial epithelium in mice were observed at 1,600 ppm. The NOAEL value corresponded to the estimated 1,4-dioxane intake of 52 mg/kg/day in rats and 170 mg/kg/day in mice.     

Lack of chronic toxicity or carcinogenicity of dietary N-acetylglucosamine in F344 rats

Chronic toxicity and carcinogenicity of N-acetylglucosamine (GlcNAc) were examined in male and female F344 rats. GlcNAc was given in the diet at levels of 0%, 1.25%, 2.5% or 5% to groups of 10 rats of each sex for 52 weeks in the chronic toxicity study and 0%, 2.5% or 5% to groups of 50 rats of each sex for 104 weeks in the carcinogenicity study. GlcNAc exerted no toxic effects with regard to clinical signs, mortality, hematology, serum biochemistry and histopathological assessment. Slight suppression of body weight gain was observed at more than 2.5%, but this appeared to be due to slight reduction of caloric intake with the high concentration of test compound, rather than any toxicity. Thus, it was concluded that GlcNAc has neither toxic nor carcinogenic effects in F344 rats, the no observed adverse effect levels (NOAEL) estimated from the chronic toxicity study being 5% in both sexes, equivalent to 2323 and 2545 mg/kg/day in males and females, respectively.     

Subchronic urinary bladder toxicity evaluation of N‐Nitrosodiphenylamine in Fischer 344 rats

Female Fischer 344 (F344) rats were exposed to N‐nitrosodiphenylamine (NDPA) by dietary feed at concentrations of 0, 250, 1000, 2000, 3000 or 4000 ppm for 5 days, 2, 4 and 13 weeks duration. Endpoints evaluated included clinical observations, body weights, urinary bladder weights, blood NDPA, gross pathology and urinary bladder histopathology. There were no NDPA exposure‐related clinical signs of toxicity. The mean body weight decreased 3% to 5% compared with the control in the 4000 ppm group during study weeks 2 through to 13. Statistically significant increases in urinary bladder weight were observed as early as after 5 days exposure and were concentration dependent at ≥ 3000 ppm. NDPA‐related urinary bladder microscopic alterations consisted of mixed cell infiltrates, increased mitosis, increased necrosis of epithelial cells, diffuse and/or nodular transitional epithelial hyperplasia and squamous metaplasia of transitional epithelium. These changes affected only rats exposed to NDPA concentrations ≥ 2000 ppm. Blood NDPA concentrations were negligible in animals exposed to ≤ 1000 ppm and ranged from 0.12 to 0.19 µg ml^–1 in rats of the ≥ 2000 ppm groups at the 5 days and 2 weeks time points. A no observable adverse effect level (NOAEL) of 1000 ppm NDPA (60 mg kg^–1 day^–1) was selected based on the absence of urinary bladder histopathology. Copyright © 2012 John Wiley & Sons, Ltd.     

Subchronic (13-Week) Toxicity Studies of Oral Phenolphthalein in Fischer 344 Rats and B6C3F1 Mice

Phenolphthalein is a cathartic agent that is widely used inover-the-counter laxatives. Thirteen-week toxicity studies ofphenolphthalein were performed using F344/N rats and B₆C₃F₁mice. Rats and mice were fed ad libitum with a NIH 07 diet containing0; 3000; 6000; 12,000; 25,000; or 50,000 ppm phenolphthalein.On a milligram per kilogram body weight basis, rats and micefed 50,000 ppm phenolphthalein ingested more drug than wouldbe expected during human laxative abuse. Phenolphthalein producedlittle evidence of toxicity in rats. There was slightly lowerweight gain among the 25,000 and 50,000 ppm groups. Treatedrats showed elevated relative kidney weights (males only) andelevated absolute and relative liver weights at 12,000–50,000ppm phenolphthalein. Rat serum bile acids were depressed early(Days 5 and 6) by phenolphthalein treatment. Several treatment-relatedtoxic effects, however, were identified in mice who receivedmore phenolphthalein per unit body weight than rats. Althoughthere were no effects on body weight gain, elevated liver weightswere noted in female mice receiving 6000–50,000 ppm phenolphthalein.The primary treatment-related findings that occurred duringthe mouse studies involved the reproductive and hematopoieticsystems. Reproductive changes including depressed testis andright epididymal weights and sperm density, an elevated productionof abnormal sperm, and morphologic alterations in seminiferoustubules occurred at all levels of exposure (3000–50,000ppm). Hematopoietic changes included bone marrow hypoplasia(12,000–50,000 ppm), increased splenic hematopoiesis (malesonly, 25,000 and 50,000 ppm), and an elevated incidence of micronucleatederythrocytes (6000–50,000 ppm).     

Toxicology and carcinogenesis studies of milk thistle extract (CAS No. 84604-20-6) in F344/N rats and B6C3F1 mice (Feed Studies)

Milk thistle extracts have been used as medicinal herbs in the treatment of liver cirrhosis, chronic hepatitis (liver inflammation), and gallbladder disorders. Treatment claims also include lowering cholesterol levels; reducing insulin resistance; reducing the growth of cancer cells in breast, cervical, and prostate gland cancers; and antiviral activity. Other reported uses of milk thistle in folk medicine include as a treatment for malarial fever, bronchitis, gallstones, jaundice, peritonitis, uterine congestion, varicose veins, and as a milk production stimulant for nursing mothers. The roots soaked in water overnight are used in food, and the despined leaves are added to salads. Roasted milk thistle fruit has been used as a coffee substitute. Milk thistle extract was nominated for study by the National Institute of Environmental Health Sciences because it is one of the most widely used herbs in the United States. Male and female F344/N rats and B6C3F1 mice were exposed to an ethanol/water extract of milk thistle fruit (milk thistle extract) containing approximately 65% silymarin in feed for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 3,125, 6,250, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 260, 525, 1,050, 2,180, or 4,500 mg milk thistle extract/kilogram body weight to males and 260, 510, 1,050, 2,150, or 4,550 mg/kg to females) for 14 weeks. All rats survived to the end of the study. Mean body weights of exposed groups were within 10% of those of the controls. Feed consumption by exposed and control groups was similar. The sperm motility in 12,500, 25,000, and 50,000 ppm males was decreased by 5%, 11%, and 9%, respectively, relative to that of the controls; the total number of spermatid heads per testis decreased by 11%, 21%, and 9% in 12,500, 25,000, and 50,000 ppm males. No significant differences in estrous cyclicity were observed between exposed and control groups of female rats. No exposure-related histopathologic lesions were observed. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were fed diets containing 0, 3,125, 6,250, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 640, 1,340, 2,500, 5,280, or 11,620 mg/kg to males and 580, 1,180, 2,335, 4,800, or 9,680 mg/kg to females) for 14 weeks. All mice survived to the end of the study. Mean body weights and feed consumption of all exposed groups were similar to those of the controls. Absolute and relative thymus weights were significantly decreased in 25,000 and 50,000 ppm males. No significant differences were observed between exposed and control groups, for sperm parameters of male mice, for estrous cyclicity of female mice, or for reproductive organ weights of male or female mice, when mice were administered milk thistle extract in feed at 12,500, 25,000, or 50,000 ppm. No exposure-related histopathologic lesions were observed. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 570, 1,180, or 2,520 mg/kg to males and 630, 1,300, or 2,750 mg/kg to females) for 105 to 106 weeks. Exposure to milk thistle extract had no effect on survival of male or female rats. Mean body weights of all exposed groups were similar to those of the controls throughout the study. Feed consumption by exposed groups of males and females was generally similar to that by the controls throughout the study. Significantly decreased incidences of mammary gland fibroadenoma, adenoma, or carcinoma (combined) occurred in females exposed to 25,000 or 50,000 ppm. Significantly increased incidences of clear cell and mixed cell focus of the liver occurred in 25,000 and 50,000 ppm females. The incidences of bile duct hyperplasia were significantly decreased in 50,000 ppm males and in all exposed groups of females, and the incidence of mixed inflammatory cell infiltration was significantly decreased in 50,000 ppm males. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 1,610, 3,530, or 7,770 mg/kg to males and 1,500, 3,175, or 7,180 mg/kg to females) for 105 to 106 weeks. Exposure to milk thistle extract had no effect on survival of male or female mice. The mean body weights of the 25,000 ppm groups were less than those of controls after week 25; mean body weights of 50,000 ppm groups were less than those of controls after week 12. Feed consumption by exposed groups of males and females was generally similar to that by the controls throughout the study. Significantly decreased incidences of hepatocellular adenoma and hepatocellular carcinoma occurred in 50,000 ppm males, and decreased incidences of hepatocellular adenoma or carcinoma (combined) occurred in 25,000 and 50,000 ppm males. GENETIC TOXICOLOGY: Five milk thistle extracts were tested independently in bacterial mutagenicity studies using a variety of S. typhimurium tester strains and one E. coli strain. Results were negative in three of the five studies, with and without exogenous metabolic activation. In two studies, milk thistle extract was mutagenic in S. typhimurium strain TA98 in the presence of exogenous metabolic activation enzymes. Silymarin, a major constituent of milk thistle extract, was positive in S. typhimurium strains TA98 and TA100, when testing occurred in the presence of exogenous metabolic activation enzymes. Silybin, another component of milk thistle extract, was negative in a S. typhimurium gene mutation assay, with and without liver S9 activation enzymes. Administration of milk thistle extract in feed for 3 months did not increase the frequencies of micronucleated normochromatic erythrocytes, an indication of chromosomal abnormalities, in the peripheral blood of male or female B6C3F1 mice. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of milk thistle extract in male or female F344/N rats or B6C3F1 mice exposed to 12,500, 25,000, or 50,000 ppm. Exposure to milk thistle extract resulted in increased incidences of clear cell and mixed cell foci in the liver of female rats and decreases in body weights of exposed groups of male and female mice. Decreased incidences of mammary gland neoplasms occurred in exposed groups of female rats, and decreased incidences of hepatocellular neoplasms occurred in exposed groups of male mice.     

Chronic toxicity tests of pyrilamine maleate and methapyrilene hydrochloride in F344 rats

Methapyrilene hydrochloride was administered at levels of 125 or 250 ppm in the diet to groups of male and female F344 rats. The closely analogous antihistaminic drug pyrilamine, as the maleate, was given at 2000 ppm in the diet or at 2 g/litre drinking-water to groups of male and female F344 rats. Almost all of the rats given the higher dose of methapyrilene had either carcinomas or neoplastic nodules of the liver, whereas at 125 ppm 40% of the rats had neoplastic nodules in the liver. Among the 20 male and 20 female rats treated with pyrilamine maleate mixed into the diet, two males and two females had hepatocellular carcinomas and, in addition, five males and eight females had neoplastic nodules in the liver. The incidence of liver neoplasms in the rats given pyrilamine in the drinking-water did not differ from that in the untreated controls, of which five males and three females had neoplastic nodules in the liver.     

Effects of Propylene Oxide on Nasal Epithelial Cell Proliferation in F344 Rats

In chronic inhalation studies, propylene oxide (PO), widelyused in the chemical and food industries, induced nasal tumorsin F344 rats. Nonneoplastic findings of the chronic studiessuggest a strong cytotoxic and proliferative component in themechanism of PO carcinogenicity. A 4-week cell proliferationstudy was conducted to establish a no-observed-adverse-effectlevel (NOAEL) for non neoplastic changes in the nasal epitheliumof rats. Male F344 rats were exposed to 0, 10, 20, 50, 150,or 525 ppm PO vapor for up to 4 weeks with up to 4 weeks ofrecovery. Histopathology showed that the incidence and severityof respiratory epithelial hyperplasia increased with exposuretime and regressed after termination of exposure with completerecovery after 4 weeks. Similarly, cell pro liferation, as determinedby bromodeoxyuridine incorporation into replicating cells, waselevated following 1 and 4 weeks of exposure, but decreasedto control values after 1 week of recovery. Degenera tion ofthe olfactory epithelium was found after 4 weeks of expo surewith a decrease in incidence and severity after terminationof exposure. Cell proliferation at this site was elevated duringthe 4-week exposure period and 1 week postexposure with returnto control values after 4 weeks of recovery. Based on the cytotoxlcand proliferative findings, the NOAEL for PO in nasal epitheliumis 50 ppm     

Toxicology and carcinogenesis studies of p,p'-dichlorodiphenyl sulfone in rats and mice.

p,p'-Dichlorodiphenyl sulfone (DDS) is used as a starting material in the production of polysulfones and polyethersufones, a family of thermoplastics. DDS was studied because of its high production volume and use. In toxicology studies, 10 Fischer 344 rats and 10 B6C3F1 mice/sex/group were fed diets containing 0, 30, 100, 300, 1,000 or 3,000 ppm DDS for 14 weeks. All animals survived until the end of the studies. Mean body weights of groups exposed to 300 ppm or greater were significantly decreased. Liver and kidney in rats and liver in mice were the major target organs of DDS toxicity. Dose-related increases in liver weights and incidences of centrilobular hepatocyte hypertrophy were observed in DDS-exposed groups. Nephropathy was seen in male and female rats only at and above 300 ppm. Neurotoxicity evaluations were negative in DDS-treated animals. Clinical chemistry and hematology parameters were minimally affected. In the 2-year toxicity and carcinogenicity studies, 50 rats and 50 mice/sex/group were fed diets containing 0, 10 (male rats), 30, 100, or 300 ppm DDS for 104 to 105 weeks. Survival of exposed groups was not affected. There were no clinical signs of toxicity related to DDS exposure. Final mean body weights were 2-17% lower in DDS-treated groups. Liver was the only target organ of DDS-induced toxicity. The incidence of centrilobular hepatocyte hypertrophy in mice and rats, and the incidence of bile duct hyperplasia and centrilobular degeneration in female rats was significantly greater than in controls. A no-observed-adverse-effect level (NOAEL) of 30 ppm DDS in the diet (1.5 mg/kg body weight) was established for rats. DDS was not carcinogenic in these studies.     

Toxicity of di(2-ethylhexyl)phthalate (DEHP) and di(2-ethylhexyl)adipate (DEHA) under conditions of renal dysfunction induced with folic acid in rats: enhancement of male reproductive toxicity of DEHP is associated with an increase of the mono-derivative

F344 male rats were given five consecutive weekly subcutaneous injections of folic acid for induction of chronic renal dysfunction and then di(2-ethylhexyl)phthalate (DEHP) or di(2-ethylhexyl)adipate (DEHA) in the diet at a concentration of 0, 6000 or 25,000 ppm for 4 weeks in order to investigate whether male reproductive toxicity of the two chemicals might be enhanced under conditions of renal disease. Control animals also received DEHP or DEHA in the same manner but without folic acid pretreatment. Decreased testicular weights, seminiferous atrophy with vacuolization of sertoli cells and diminished sperm counts were more prominent in rats given folic acid and then 25,000 ppm DEHP as compared to those exposed to DEHP alone. No such reproductive toxicity was evident in rats given 6000 ppm DEHP or either dose of DEHA. An increased concentration of the mono-derivative of DEHP (mono(2-ethylhexyl)phthalate, MEHP) in the blood, testis and urine was considered relevant to the enhanced reproductive toxicity observed with DEHP.     

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.     

Long-term feeding study of N,N'-diphenyl-p-phenylenediamine in F344 rats

Groups of 50 F344 rats of each sex were fed a diet containing 0.5 or 2% of N,N'-diphenyl-p-phenylenediamine (DPPD) for 104 weeks and were killed 8 weeks after the cessation of DPPD administration. DPPD-treated rats of both sexes showed a dose-dependent reduction in body weight gain, but no lower survival rate, when compared with untreated control rats. Blood and urine analysis showed no remarkable changes due to the treatment. Calcium deposition in the kidney of males was the only significant histological change relating to the treatment. Tumors were found in many organs of all groups, but a significant increase of tumor induction in DPPD-treated groups was not observed.     

Nasal epithelial lesions in F344 rats following a 90-day inhalation exposure to naphthalene

Naphthalene (NA) was shown to be carcinogenic, causing respiratory epithelial adenoma in the nasal cavity of male F344 rats and olfactory epithelial neuroblastoma in female F344 rats at exposure concentrations of 10-60?ppm in a 2-year inhalation study conducted by the National Toxicology Program. To explore the exposure-response relationship and threshold for nasal epithelial effects in F344 rats, a 90-day (6?h/d, 5?d/wk) inhalation study was conducted at 0, 0.1, 1, 10 and 30?ppm NA vapor. Group size for nasal cavity histopathology was 10/sex with an additional 10/sex evaluated 4?wk post-exposure. NA exposure concentrations were measured by GC/MS, and aerosol testing verified that solid NA particles were not present. There were no NA exposure-related clinical observations and mild decreases in body weight (<10%) and food/water consumption were observed primarily in the 30?ppm rats. Rat heads were cross-sectioned at six levels for microscopic examination. There were no nasal cavity lesions related to NA exposure in rats of the 0.1?ppm group. Minimal hyperplasia was observed in the transitional/respiratory epithelium of rats exposed to 1?ppm. Mild hyperplasia and minimal squamous metaplasia were observed in the respiratory epithelium of rats exposed to 10 or 30?ppm. Lesions in the olfactory epithelium were observed only in rats of the 10 or 30?ppm groups and consisted of degeneration, necrosis, areas of re-epithelialization and basal cell hyperplasia. There was remarkable recovery of effects after 4 weeks, but residual olfactory epithelial degeneration and basal cell hyperplasia were still evident.     

Dose-threshold for thyroid tumor-promoting effects of xylazine in rats

To clarify the threshold dose of thyroid tumor-promoting effects of xylazine hydrochloride (XZ), male F344 rats received pulverized basal diet containing 0, 250, 500, or 1000 ppm XZ for 26 weeks with or without initiation of 2400 mg/kg N-bis(2-hydroxypropyl)nitrosamine (DHPN). Thyroid weights significantly increased in the groups with or without DHPN initiation that were given 500 ppm XZ or more. The serum thyroxine (T4) and triiodothyronine (T3) levels decreased significantly in the XZ 250 and XZ 1000 ppm groups, respectively, although there were no remarkable changes in the serum thyroid-stimulating hormone (TSH) levels. Histopathologically, follicular cell hyperplasias and adenomas were induced in the DHPN-alone and DHPN+XZ groups, and the incidences and multiplicities of these lesions in the DHPN groups treated with 500 ppm XZ or more were significantly higher than those in the DHPN alone group. These results suggest that the threshold dose of rat thyroid tumor-promoting effects of XZ is between 250 and 500 ppm under the present experimental condition.     

Influence of dietary zinc on di(2-ethylhexyl)phthalate-induced testicular atrophy and zinc depletion in adult rats

Groups of 48 adult male F344 rats were maintained on synthetic diets containing 20 ppm (normal), 2 ppm (low), or 200 ppm (high) zinc. After 1 week of acclimation to the various diets, groups of 12 rats from each dietary regimen were gavaged for 13 consecutive days with 0.0 (vehicle), 0.33, 1.0, or 3.0 g/kg di(2-ethylhexyl)phthalate (DEHP). These were selected as relatively nontoxic, mildly toxic, and moderately toxic doses for producing testicular injury in adult male rats. At termination on the 14th day, body weight gain was reduced by 3.0 g/kg DEHP dose in the normal and low-zinc diet groups but not in the high-zinc diet group. The low-zinc diet alone reduced body weight gain, independent of DEHP treatment. DEHP had no perceptible effects on the weights of testis, seminal vesicle, prostate, or epididymis from rats maintained on normal- or high-zinc diets, but reduced the weights of all of these organs from animals on the low-zinc diet in a dose-dependent manner. Lactate dehydrogenase activity, total and free sulfhydryl contents, and zinc concentrations in testes were also reduced, and testicular degeneration was induced by DEHP in the low-zinc diet groups. In contrast, dose-dependent liver enlargement and hypolipidemia (reduction of serum cholesterol and triglyceride concentrations) were produced by equivalent doses of DEHP in all of the three zinc groups. The selectively enhanced susceptibility of adult male F344 rats on a zinc deficient diet to the gonadotoxic effects of DEHP supports the hypothesis that testicular zinc depletion is causally related to the ensuing testicular and accessory sex organ atrophies. Other biological effects of DEHP (e.g., hypolipidemia, hepatomegaly) appear to occur independent of zinc homeostasis.     

Two-generation reproductive toxicity study of aluminium sulfate in rats

In a two-generation reproductive toxicity study, male and female rats were given aluminium sulfate (AS) in drinking water at 0, 120, 600 or 3000 ppm. AS reduced water consumption in all treatment groups, and body weight was transiently decreased in the 3000 ppm group. In the F1 and F2 pups, preweaning body weight gain was inhibited at 3000 ppm, and the liver and spleen weight was decreased at weaning. At this dose, vaginal opening was slightly delayed. There were no compound-related changes in other reproductive/developmental parameters, including developmental neurobehavioral endpoints. The data indicated that the NOAEL of AS in this two-generation study is 600 ppm for parental systemic toxicity and reproductive/developmental toxicity. The total ingested dose of aluminium from drinking water and food (standard rat diet, containing 25-29 ppm of aluminium) combined for this 600 ppm group was calculated to be 8.06 mg Al/kg bw/day.