Toxicology of 1,1,2-trichloroethane in the mouse

1,1,2-Trichloroethane (TCE) was administered to male and female CD-1 mice to evaluate its effect on standard toxicological parameters. Following determination of the acute LD50 (378 mg/kg in males and 491 mg/kg in females), and a 14-day range-finding study, a 90-day drinking water study was performed in which the doses consumed were 4.4, 46, and 305 mg/kg for males and 3.9, 44, and 384 mg/kg for females. The liver was a target of TCE toxicity in both sexes as demonstrated by dose-dependent alterations in hepatic microsomal enzyme activities and serum enzyme levels. The erythroid element of the female mice was also affected, as indicated by significantly decreased hematocrit and hemoglobin levels.     

Humoral and Cell-Mediated Immune Status of Mice Exposed to Trans-1,2-Dichloroethylene

ABSTRACT

This study assessed possible adverse immunological effects of trans-1,2-dichloroethylene (DCE) on random-bred CD-I mice following 14 and 90 days of exposure. A 14-day range-finding study was performed on male mice by gavage at doses 1/10 and 1/100 the LD50 (210 and 21 mg/kg). No alterations in either humoral or cell-mediated immunity were observed following this exposure. A 90-day study was conducted in which DCE was administered in the drinking water of male and female mice. The levels of DCE in the drinking water were calculated to deliver levels equivalent to, and higher than, those delivered for 14 days (17, 175, and 387 mg/kg for males and 23, 224, and 452 mg/kg for females). No changes were observed in the cell-mediated immune status of either sex or in the humoral immune status of females. However, a marked suppression in humoral immune status was observed in male mice exposed to all three levels of DCE, as indicated by a decreased ability of spleen cells to produce antibody against sheep erythrocytes (sRBC). Macrophage function was depressed only in females, as indicated by the decreased ability of thioglycollate-recruited peritoneal exudate cells (PEC) to phagocytize sRBC.     

Humoral and Cell-Mediated Immune Status of Mice Exposed to 1,1,2-Trichloroethane

ABSTRACT

The purpose of this study was to assess the immunological effects of 1,1,2-trichloroethane (TCE) on random-bred CD-I mice following 14 and 90 days of oral exposure. A toxicological evaluation conducted at the same time revealed the target organs to be the liver of both sexes and the erythroid elements of the females. The 14-day immunological range-finding study in males exposed to doses 1/10 and 1/100 the LD50 (38 and 3.8 mg/kg) revealed no alterations in either humoral or cell-mediated immune status. Following 90 days of exposure in the drinking water (4.4., 46, and 305 mg/kg for males and 3.9, 44, and 384 mg/kg for females), a more detailed series of immunological parameters was assessed. Cell-mediated immunity was unaltered in both sexes, while humoral immune status was depressed in both sexes, particularly when determined by hemagglutination titers. Macrophage function was depressed only in the males as indicated by the ability of thioglycolate-recruited peritoneal exudate cells (PEC) to phagocytize sheep erythrocytes (sRBC).     

Toxicity Studies of 1,3-Dichlorobenzene in Sprague-Dawley Rats

ABSTRACT

Male and female Sprague-Dawley rats received 1,3-dichlorobenzene daily by corn oil gavage for 10 or 90 consecutive days. The 10-day study doses were 0, 37, 147, 368 and 735 mg/kg; the 90-day study doses were 0, 9, 37, 147 and 588 mg/kg. In the 10-day study, there was a significant depression of body weight in both sexes at 735 mg/kg. Liver weights were significantly increased in both sexes at 368 and 735 mg/kg. Serum cholesterol levels were significantly elevated in both sexes at 368 and 735 mg/kg. Histopathological evaluation revealed centrolobular hepatocellular degeneration at 368 mg/kg in males and 735 mg/kg in females.

In the 90-day study, body weights were significantly depressed in both sexes at 588 mg/kg. Normalization of food and water consumption by final body weight indicated that at 588 mg/kg both sexes had increased food and water consumption relative to controls. Absolute and relative liver weights were significantly increased in both sexes at 147 and 588 mg/kg. Relative kidney weights were significantly higher in both sexes at 588 mg/kg and in males at 147 mg/kg. Serum cholesterol and calcium levels were significantly elevated over controls in females at 37,147, and 588 mg/kg, and in males at all dose levels. Histopathological evaluation at 147 and/or 588 mg/kg demonstrated liver and thyroid lesions in both sexes, and pituitary and kidney lesions in males. A NOAEL was not firmly established.     

A comparison of the pulmonary toxicity produced by metal-free and copper-complexed analogs of bleomycin and phleomycin

The purpose of this study was to evaluate the acute and subchronic toxicology of trichloroethylene (TCE) in the mouse. The oral LD50 in female mice was 2443 mg/kg (95% confidence limits of 1839–3779 mg/kg) and in male mice was 2402 mg/kg (95% confidence limits of 2065–2771 mg/kg). After determination of the LD50 by the oral route, a 14-day study was done in male CD-1 mice in which TCE was administered daily by gavage at 24 and 240 mg/kg. A subchronic drinking water study was designed based on these data, in which TCE at concentrations of 0.1, 1.0, 2.5, and 5.0 mg/ml was used, and mice of both sexes were exposed for 4 or 6 months. There was a decreased body weight gain at the highest dose, which could be attributed to a decrease in fluid consumption. The most significant effects attributable to TCE were an increase in liver weight in both sexes accompanied by increased nonprotein sulfhydryl levels in the males, and an increase in kidney weight in both sexes accompanied by increases in protein and ketones in the urine. TCE failed to elicit any other adverse effects.     

Differing hepatotoxicity and lethality after subacute trichloroethylene exposure in aqueous or corn oil gavage vehicles in B6C3F1 mice

Subacute toxicity of trichloroethylene (TCE) was evaluated in male and female B6C3F1 mice using corn oil or aqueous gavage vehicles. Mice received oral doses of TCE five times a week for 4 weeks at 600, 1200 and 2400 mg/kg/day for males and 450, 900 and 1800 mg/kg/day for females. Vehicle control mice were dosed with either corn oil or a 20% aqueous solution of Emulphor. A dose-related increase in lethality occurred in male and female mice receiving TCE in Emulphor but not corn oil during the first week of treatment. Lethality was consistent with central nervous system depressant effects of TCE. After 4 weeks of exposure, body weights were not altered by TCE but liver/body weight ratios were uniformly increased by TCE administered in either vehicle in both sexes. Only male mice treated with TCE in corn oil, however, sustained elevations in serum enzyme levels, accompanied by liver histopathology. TCE in corn oil produced inflammation-associated focal necrosis in 30-40% of the male mice, with increasing severity from low to high dose. Lipid accumulation, as indicated by Oil-Red O staining, was most prevalent in male mice treated with TCE in corn oil but also occurred to a lesser degree in animals receiving either gavage vehicle alone. This study indicates that the type of oral gavage vehicle is an important factor in determining the nature of TCE toxicity.     

Humoral and cell-mediated immune status in mice exposed to trichloroethylene in the drinking water

A 14-day study using male CD-1 mice exposed to trichloroethylene (TCE) by daily po gavage suggested inhibition of cell-mediated immunity. Therefore, an evaluation of the immune status was undertaken after exposure of male and female mice to TCE in the drinking water for either 4 or 6 months. The immunological parameters assessed were humoral immunity, cell-mediated immunity, lymphocyte responsiveness, bone marrow function, and macrophage function. Females were more affected than males by TCE, particularly after a 4-month exposure. In the female, humoral immunity was inhibited only at the highest concentrations of TCE (2.5 and 5 mg/ml), whereas cell-mediated immunity and bone marrow stem cell colonization were inhibited at all four concentrations of TCE (0.1, 1.0, 2,5, and 5 mg/ml). The males were relatively unaffected after both 4 and 6 months compared to effects observed in the 14-day study.     

Humoral and cell-mediated immune status of mice exposed to 1,1,2-trichloroethane

The purpose of this study was to assess the immunological effects of 1,1,2-trichloroethane (TCE) on random-bred CD-1 mice following 14 and 90 days of oral exposure. A toxicological evaluation conducted at the same time revealed the target organs to be the liver of both sexes and the erythroid elements of the females. The 14-day immunological range-finding study in males exposed to doses 1/10 and 1/100 the LD50 (38 and 3.8 mg/kg) revealed no alterations in either humoral or cell-mediated immune status. Following 90 days of exposure in the drinking water (4.4., 46, and 305 mg/kg for males and 3.9, 44, and 384 mg/kg for females), a more detailed series of immunological parameters was assessed. Cell-mediated immunity was unaltered in both sexes, while humoral immune status was depressed in both sexes, particularly when determined by hemagglutination titers. Macrophage function was depressed only in the males as indicated by the ability of thioglycolate-recruited peritoneal exudate cells (PEC) to phagocytize sheep erythrocytes (sRBC).     

Humoral and cell-mediated immune status of mice exposed to trans-1,2-dichloroethylene

This study assessed possible adverse immunological effects of trans-1,2-dichloroethylene (DCE) on random-bred CD-1 mice following 14 and 90 days of exposure. A 14-day range-finding study was performed on male mice by gavage at doses 1/10 and 1/100 the LD50 (210 and 21 mg/kg). No alterations in either humoral or cell-mediated immunity were observed following this exposure. A 90-day study was conducted in which DCE was administered in the drinking water of male and female mice. The levels of DCE in the drinking water were calculated to deliver levels equivalent to, and higher than, those delivered for 14 days (17, 175, and 387 mg/kg for males and 23, 224, and 452 mg/kg for females). No changes were observed in the cell-mediated immune status of either sex or in the humoral immune status of females. However, a marked suppression in humoral immune status was observed in male mice exposed to all three levels of DCE, as indicated by a decreased ability of spleen cells to produce antibody against sheep erythrocytes (sRBC). Macrophage function was depressed only in females, as indicated by the decreased ability of thioglycollate-recruited peritoneal exudate cells (PEC) to phagocytize sRBC.     

Lifetime toxicity/carcinogenicity study of FD & C Red No. 3 (erythrosine) in mice

Charles River CD-1 mice were fed FD & C Red No. 3 in the diet at levels of 0.3, 1.0 and 3.0% in a long-term toxicity/carcinogenicity study. Each group consisted of 60 males and 60 females. Two concurrent control groups each of 60 males and 60 females received the basal diet. Maximum exposure was 24 months. The no-adverse-effect levels established in this study were 3.0% (an average intake of 4759 mg/kg/day) for male mice and 1.0% (1834 mg/kg/day) for female mice.     

Subchronic Toxicology of Diethystilbestrol in the Mouse

ABSTRACT

This study evaluated the subchronic (14-day) toxicity of selected (0.2, 1.0, and 4.0 mg/kg) daily subcutaneous injections of diethylstilbestrol (DES) in female (C₅₇Bl/6 × C₃H)F₁ mice. Parameters observed included body and organ weights, gross organ morphology, histopathology, clinical chemistry, and hepatic microsomal enzyme activities. The liver, bone marrow, and thymus are major target organs for DES. Liver enlargement, with associated histopathological changes consistent with mild hepatitis, centrolobular necrosis, and sinusoidal changes were observed. Supporting the histological changes were alterations in serum enzyme levels and microsomal enzyme activity. Bone marrow changes included decreases in the number of cells as well as the number of colony forming units per gram stem cells. Toxicity to the thymus was evidenced by decreased thymic weights and lymphocyte depletion. The hepatic and thymic effects were observed at the lowest (0.2 mg/kg) dose. Although all parameters were not assessed for recovery, those that were evaluated returned to control levels by thirty days after treatment.     

A chronic toxicity/carcinogenicity study of FD & C Yellow No. 5 (tartrazine) in mice

Charles River CD-1 mice were fed FD & C Yellow No. 5 in the diet at levels of 0.0, 0.0, 0.5, 1.5 or 5.0% in a long-term toxicity/carcinogenicity study. Each group consisted of 60 males and 60 females. Maximum exposure was 104 wk for both males and females. No consistent, significant compound-related adverse effects were noted. The no-observed-adverse effect level established in this study was 5.0% (8103 mg/kg/day and 9735 mg/kg/day for male and female mice, respectively.)     

Subacute and subchronic toxicity of ethylene glycol administered in drinking water to Sprague-Dawley rats

Subacute (10-day) and subchronic (90-day) toxicity studies of ethylene glycol (EG) were conducted in male and female Sprague-Dawley rats to provide the U.S. Environmental Protection Agency's (EPA) Office of Drinking Water with toxicity data for final preparation of a Health Advisory for the chemical. Ethylene glycol was administered in drinking water at concentrations of 0.5, 1.0, 2.0, and 4.0% for both sexes in the 10-day study. Based on a projected consumption rate of 100 ml/kg/day, the respective doses on a mg/kg/day basis would be 554, 1108, 2216, and 4432. These dose levels were also used in the 90-day study for females, but dose levels for the males in the 90-day study were 0.25, 0.5, 1.0, and 2.0% (227, 554, 1108, and 2216 mg/kg/day). At time of sacrifice necropsies were performed and tissues were prepared for histological evaluation. Blood samples were taken for hematology and clinical chemistry determinations. Body weights were measured weekly. Water and food consumption were determined three times weekly. No mortality occurred in the 10-day study. In the 90-day study 8/10 females and 2/10 males in the high dose group died prior to sacrifice. Body weights were suppressed in a dose response fashion for males and females. Hemoglobin, hematocrit, erythrocytes, and leukocytes were all significantly decreased in female rats receiving 4% EG for 10 days. The most significant histopathological findings, seen predominantly in males, were kidney lesions which included calcium oxalate crystals in tubules and pelvic epithelium; tubular dilation and degeneration; intratubular proteinaceous material; and inflammation in tubules and pelvic epithelium. At the same dose of ethylene glycol, males had more kidney lesions and much higher incidence and severity of lesions than the females.     

Male olfactory cues affect mothers’ behavior in mice: effects of benzodiazepines

Rationale: Threatening social stimuli were used in this study as aversive conditions to test anxiety in lactating female mice. The odors of potential infanticidal males or the ”stress odor” left by restrained mice represented two aversive conditions that have been suggested to modulate the time spent by the mothers to reach their pups after 30 min of separation. Objectives: The effects of drugs acting at the benzodiazepine receptors were evaluated on the behavior of mothers exposed to different threatening social cues. Methods: Lactating mice of the NMRI outbred strain with 8-day old pups were treated with (1) chlordiazepoxide (CDP) 2.5, 5.0 and 10 mg/kg i.p.; (2) flumazenil 10 mg/kg i.p. and (3) methyl β-carboline-3-carboxylate (β-CCM) 3.0 mg/kg i.p. Results: The odors left by stressed females changed the mothers’ exploratory behavior, but not the latency to reach pups. The latency was higher in the presence of cues from potentially infanticidal males. CDP (5.0 mg/kg) reduced the time spent to contact pups, whereas the other CDP doses did not modify the dam’s behavior. Flumazenil, given in combination with CDP (5.0 mg/kg) antagonized the latter anxiolytic effect. In addition, in the presence of cues from potentially infanticidal males β-CCM had anxiogenic activity, increasing latency to reach pups. The same CDP and β-CCM doses were ineffective in the presence of cues from stressed females and in the absence of olfactory cues from conspecifics. Conclusions: This study provides behavioral and pharmacological validation of a new model of anxiety specifically designed for lactating females. Received: 21 January 1999 / Final version: 22 April 1999     

Toxicology and carcinogenesis studies of pulegone (CAS No. 89-82-7) in F344/N rats and B6C3F1 mice (gavage studies)

Several essential oils contain pulegone and are used for flavoring foods, drinks, and dental products, as fragrance agents, and in herbal medicines. Pulegone was nominated for study by the National Institute of Environmental Health Sciences based on the potential for human exposure and the absence of carcinogenicity data. Male and female F344/N rats and B6C3F1 mice received pulegone (approximately 96% pure) by gavage for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were administered 0, 37.5, 75, 150, 300, or 600 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 16 days. All male rats and nearly all female rats in the 300 and 600 mg/kg groups died prior to the end of the study. All moribund sacrifices and early deaths were attributed to liver toxicity. Mean body weight gains of males administered 37.5 or 150 mg/kg were significantly less than that of the vehicle controls. Clinical findings in 300 and 600 mg/kg rats included nasal/eye discharge, thinness, lethargy, and ruffled fur. Liver and kidney weights of dosed groups of females were generally significantly greater than those of the vehicle control group. The incidences of necrosis and cytoplasmic vacuolization of the liver in 300 and 600 mg/kg males and females were significantly greater than those in the vehicle control groups. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were administered 0, 18.75, 37.5, 75, 150, or 300 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 16 days. Four females and one male in the 300 mg/kg groups died by study day 5. All early deaths were attributed to liver toxicity. Mean body weights of the dosed groups were similar to those of the vehicle controls. Clinical findings were observed only in 300 mg/kg mice and included thinness, lethargy, and ruffled fur. Liver weights of 300 mg/kg males were significantly greater than those of the vehicle controls. The incidences of cytoplasmic vacuolization and diffuse fatty change in 300 mg/kg females and necrosis in 300 mg/kg males were significantly greater than those in the vehicle controls. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered 0, 9.375, 18.75, 37.5, 75, or 150 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. All rats survived until the end of the study except for one female in the 150 mg/kg group that died on day 9. Mean body weights of 75 and 150 mg/kg males and 150 mg/kg females were significantly less than those of the vehicle controls. At the end of the study, there was a small dose-related decrease in the erythron, evidenced by decreases in the hematocrit and hemoglobin values and the erythrocyte counts. An apparent erythroid response to the decreased erythron was evidenced by increased reticulocyte counts. Reduced and oxidized glutathione levels were generally increased in 75 and 150 mg/kg males and in 37.5 mg/kg or greater females. Absolute and relative liver weights of 75 and 150 mg/kg females and relative liver weights of males administered 18.75 mg/kg or greater were significantly greater than those of the vehicle controls. The absolute kidney weight of 150 mg/kg females and the relative kidney weights of all dosed groups, except 9.375 mg/kg males, were significantly greater than those of the vehicle controls. Absolute and relative thymus weights of 150 mg/kg males and females and the absolute thymus weight of 75 mg/kg males were significantly less than those of the vehicle controls. In the kidney, there was hyaline glomerulopathy in 75 mg/kg males and 150 mg/kg males and females. The incidence of renal tubule protein casts was significantly increased in the 150 mg/kg females. In the liver, incidences of bile duct hyperplasia and hepatocyte hypertrophy in 75 and 150 mg/kg males and 150 mg/kg females, hepatocyte focal necrosis in 150 mg/kg males, and oval cell hyperplasia and periportal fibrosis in 150 mg/kg males and females were increased. Incidences of bone marrow hyperplasia in 37.5 mg/kg males and 75 and 150 mg/kg males and females, heart mineralization in 150 mg/kg males, glandular stomach mineralization in 75 and 150 mg/kg females, and cellular histiocytic infiltration in the lung and ovarian cyst in 150 mg/kg females were significantly increased. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered 0, 9.375, 18.75, 37.5, 75, or 150 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of dosed mice were similar to those of the vehicle controls. Reduced and oxidized glutathione levels were generally greater than vehicle control levels in 150 mg/kg males and in 75 and 150 mg/kg females. Liver weights of 150 mg/kg males and 75 and 150 mg/kg females were significantly greater than those of the vehicle controls. No histopathologic lesions were observed that could be attributed to the administration of pulegone. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0, 18.75 (males only), 37.5, 75, or 150 (females only) mg pulegone/kg body weight in corn oil by gavage, 5 days per week for up to 104 weeks. Due to excessive morbidity and mortality, 75 mg/kg males and 150 mg/kg females were not administered pulegone after week 60 (stop-exposure); these groups were administered the corn oil vehicle until the end of the study. Survival of 37.5 mg/kg males was significantly less than that of the vehicle controls; only two 75 mg/kg stop-exposure males survived, and no 150 mg/kg stop-exposure females survived to the end of the study. Compared to those of the vehicle controls, mean body weights were less in 75 mg/kg stop-exposure males after week 13 and in 75 mg/kg and 150 mg/kg stop-exposure females after weeks 21 and 9, respectively. Clinical findings included thinness, lethargy, and ruffled fur in the 75 mg/kg stop-exposure males and 150 mg/kg stop-exposure females. The incidences of urinary bladder papilloma and of papilloma or carcinoma (combined) were significantly increased in 150 mg/kg stop-exposure females. In the kidney, incidences of hyaline glomerulopathy were significantly increased in 37.5 mg/kg and 75 mg/kg stop-exposure males and in all dosed groups of females. The severity of chronic progressive nephropathy was increased in 37.5 mg/kg and 75 mg/kg stop-exposure males and in 75 mg/kg and 150 mg/kg stop-exposure females; the incidences of nephropathy were significantly increased in 75 mg/kg and 150 mg/kg stop-exposure females. The incidence of renal cyst was significantly increased in 75 mg/kg stop-exposure males. In the liver, incidences of diffuse hepatocyte cellular alteration were significantly increased in 37.5 mg/kg and 75 mg/kg stop-exposure males and 75 mg/kg and 150 mg/kg stop-exposure females. There were significant increases in the incidences of other liver lesions including fatty change, bile duct cyst, hepatocyte necrosis, oval cell hyperplasia, bile duct hyperplasia, and portal fibrosis. In the nose, 37.5 mg/kg and 75 mg/kg stop-exposure males and all dosed groups of females had significantly increased incidences of olfactory epithelium degeneration. All dosed groups of females had significantly increased incidences of respiratory metaplasia of the olfactory epithelium and nasal inflammation. In the forestomach, incidences of inflammation and ulcer were significantly increased in 37.5 mg/kg and 75 mg/kg stop-exposure males, and incidences of epithelial hyperplasia and perforation were increased in 75 mg/kg stop-exposure males. In the glandular stomach, the incidence of inflammation was significantly increased in 75 mg/kg stop-exposure males. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 0, 37.5, 75, or 150 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 105 weeks. Survival of all dosed groups was similar to that of the vehicle controls. Mean body weights of 150 mg/kg males and females were less than those of the vehicle controls after weeks 25 and 33, respectively. The incidences of multiple hepatocellular adenoma were significantly increased in all dosed groups of males, and the incidences of hepatocellular adenoma (includes multiple) and hepatoblastoma (includes multiple) were significantly increased in the 75 mg/kg males. The combined incidences of hepatocellular adenoma, hepatocellular carcinoma, or hepatoblastoma occurred with positive trends and were significantly increased in 75 mg/kg males and 150 mg/kg females. The incidence of hepatocellular adenoma was significantly increased in 150 mg/kg females. The incidences of several nonneoplastic liver lesions were significantly increased, primarily in the 75 and 150 mg/kg groups. These nonneoplastic lesions included clear cell, eosinophilic, and mixed cell foci; focal fatty change; centrilobular hepatocyte hypertrophy; intravascular hepatocyte; necrosis; pigmentation; bile duct cyst and hyperplasia; and oval cell hyperplasia. In the kidney, incidences of hyaline glomerulopathy were significantly increased in all dosed groups of males and 75 and 150 mg/kg females. The incidence of mineralization was significantly increased in 150 mg/kg females, and the incidence of nephropathy in 150 mg/kg females and severity of nephropathy in 150 mg/kg males were increased. Incidences of congestion of the glomerulus were increased in 150 mg/kg males and females. The incidence of osteoma or osteosarcoma (combined) in all organs of 75 mg/kg females exceeded the historical control ranges. One 150 mg/kg male and one 75 mg/kg female had nasal osteoma; no nasal osteomas have been observed in historical control mice. (ABSTRACT TRUNCATED)     

Lifetime toxicity/carcinogenicity studies of FD & C Blue No. 1 (brilliant blue FCF) in rats and mice

FD & C Blue No. 1 was fed to Charles River CD rats and CD-1 mice as a dietary admixture in lifetime toxicity/carcinogenicity studies. The rat study was conducted with an in utero phase in which the compound was administered to the F0 generation rats (60/sex/group) at dietary concentrations of 0.0%, 0.0%, 0.1%, 1.0% or 2.0%. After randomly selecting the F1 animals, the lifetime phase was initiated at the same levels with 70 rats/sex/group, including two control groups. The maximum exposure times were 116 and 111 wk for males and females, respectively. The no-observed-adverse-effect levels are dietary concentrations of 2.0% for males (1072 mg/kg body weight/day), and 1.0% for females (631 mg/kg/day) based on a 15.0% decrease in terminal body weight and decreased survival in the high-dose females compared with the combined control groups. Charles River CD-1 mice (60/sex/group) were fed FD & C Blue No. 1 as a dietary admixture at levels of 0.0%, 0.0%, 0.5%, 1.5% or 5.0% in a lifetime toxicity/carcinogenicity study. The maximum exposure time was 104 wk for both males and females. No consistent, significant compound-related adverse effects were noted. The no-observed-adverse-effect level established in this study is a dietary concentration of 5.0% (7354 mg/kg/day and 8966 mg/kg/day for male and female mice, respectively.     

Differential toxicity of aflatoxin B1 in male and female rats: relationship with hepatic drug-metabolizing enzymes

It is well known that distinct differences in the metabolism of xenobiotics exist between males and females of the same species. Male and female rats were treated with a single intraperitoneal dose of aflatoxin B₁ (AFB₁): 1 or 3 mg/kg for males, 3 or 6 mg/kg for females. Comparative changes in hepatic drug metabolizing and plasma enzymes had been studied. The obtained results show that, at the common dose of 3 mg/kg, AFB₁ induced an 18% mortality in males and none in females. In the plasma, total bilirubin concentration as well as the activity of transaminases and alkaline phosphatase (ALP), utilized as indicators of liver damage, were highly increased in both males and females due to the treatment with 3 or 6 mg AFB₁/kg. In the female, the plasma features rapidly declined. In contrast, in the male, the effect of AFB₁ was prolonged. Hepatic determinations revealed a pattern difference of drug metabolizing enzymes and cytochrome P-450 between males and females. The results also show that in the male, most of the drug metabolizing enzyme activities were decreased until the ninth day with the 3 mg/kg treatment. So, we observed a decrease in the activities of UDP-glucuronosyltransferase (UDPGT) with p-nitrophenol as substrate (PNP) and GSH S-transferase, 40 and 53% respectively; while the activity of epoxide hydrolase was increased up to 170%. In the meantime, the concentration of cytochrome P-450 decreased by 69%. By contrast, in the case of the female, these decreases were only 14, 43 and 23% for the UDPGT, GSH S-transferase and cytochrome P-450, respectively. Moreover, these decreases occurred only during the first three days after treatment. Thereafter, these enzyme activities significantly increased above the control values. This study suggests that the induction of detoxicating enzymes, more important in the female (72% increase in the activity of UDPGT, 480% in that of epoxide hydrolase and 42% for GSH S-transferase, may have a protective role against AFB₁ metabolites and could explain, partly, the lower sensitivity of the female to the toxic effects of AFB₁.     

Tumor induction in mouse liver: di-isononyl phthalate acts via peroxisome proliferation

Recently several chronic toxicity/carcinogenicity studies of di-isononyl phthalate (DINP) have been reported. These studies defined effect levels for liver tumors in male and female F344 rats at dietary levels exceeding 700 mg/kg/day; the no effect levels were 359 mg/kg/day in males and 442 mg/kg/day in females. Similar results were found in male B6C3F1 mice, but in female mice a significant increase in liver tumors was found at 336 mg/kg/day, making 112 mg/kg/day the NOAEL for liver tumors in that sex and species. DINP induces peroxisomal proliferation, and that, along with evidence that DINP is not mutagenic, is presumptive evidence for peroxisomal proliferation as the underlying mode of action for liver tumor development. To further explore the relationship between peroxisome proliferation and tumor induction in male and female mice, indicators of peroxisomal proliferation including liver weight, peroxisomal volume density, induction of peroxisomal enzyme activity, enhanced replicative DNA synthesis, and rates of apoptosis were measured at all of the dietary levels used in the chronic study in mice (500, 1500, 4000, and 8000 ppm, or approximately 100, 300, 800, and 1600 mg/kg/day). Liver weights, peroxisomal volume, and peroxisomal enzyme activity were significantly elevated in both male and female mice at the tumorigenic levels. Cell proliferation was also elevated in male and female mice, although the increases at levels below 4000 ppm in female mice were not significantly different from control values. Apoptosis was elevated at the 4000 and 8000 ppm levels, paralleling the increases in liver weight. These data along with previous results satisfy the criteria of the International Agency for Research on Cancer (IARC) and demonstrate that peroxisomal proliferation was indeed the mode of action for DINP-induced liver tumor induction in mice.