Evaluation of subchronic inhalation toxicity of methylcyclopentane in rats

The aim of this study was to verify subchronic inhalation toxicity of methylcyclopentane (CAS No. 96-37-7) in Sprague-Dawley rats. Four groups of 10 rats of each gender were exposed to methylcyclopentane vapor by whole-body inhalation at concentrations of 0, 290, 1300, or 5870 ppm for 6 h per day, 5 days/week over a 13-week period. During the study period, clinical signs, mortality, body weight, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross pathology, organ weights, and histopathology were examined. Exposure-related clinical signs (salivation and rubbing) were observed in both genders of the 5870 ppm group. There was an increase in liver weight for both genders but the kidney weight was only higher in females than controls. However, no toxicologically significant changes were observed in body weight, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, necropsy findings, or histopathology in any of the treatment groups. Under the present experimental conditions, the target organs were determined to be kidney and liver in rats. The no-observed-adverse-effect concentration was considered to be 1300 ppm/6 h/day in rats.     

Prechronic Inhalation Toxicity Studies of Isobutyl Nitrite

Isobutyl nitrite (IBN) is a volatile liquid that has becomeincreasingly popular as an inhaled recreational drug. To investigateshort-term toxic effects and establish exposure parameters forchronic inhalation studies, F344/N rats and B6C3F1 mice wereexposed to IBN vapors on a 6 hr/day + t90, 5 days/week schedule.Twelve exposures were administered at concentrations of 0, 100,200, 400, 600, and 800 ppm IBN. This exposure series resultedmortality in rats exposed to 600 ppm and mice exposed to 800ppm. Animals exposed at the lower concentrations developed hyperplasiaof the bronchiolar and nasal turbinate epithelium (rats andmice) and lymphocytic atrophy in the spleen and thymus (mice).Longer term, 13-week, subchronic exposures were conducted atconcentrations of 0, 10, 25, 75, 150, and 300 ppm IBN. Exposureto 300 ppm IBN reduced the body weight gains in both sexes ofrats and in female mice. IBN-related clinical pathology changesincluded reduced RBC counts accompanied by moderate increasesin mean corpuscular volume and reticulocyte counts, increasedWBC counts, and mildly increased methemoglobin concentration.Bone marrow hyperplasia was observed in all groups of IBN-exposedrats, while in mice only females at l50 ppm IBN displayed thischange. Excessive splenic pulp hematopoiesis was noted in miceat all IBN exposure levels. Respiratory system changes includedincreased lung weights in rats and female mice at 300 ppm, hyperplasiaof the nasal mucosa (male rats at 75 ppm and female rats at150 ppm), and hyperplasia of the lung epithelium (male miceat 150 ppm and female mice at 75 ppm). The results suggestedthat a concentration of 150 ppm could be used as the highestexposure level for subsequent chronic inhalation tests.     

Evaluation of propargyl alcohol toxicity and carcinogenicity in F344/N rats and B6C3F1/N mice following whole-body inhalation exposure

Propargyl alcohol (PA) is a high production volume chemical used in synthesis of many industrial chemicals and agricultural products. Despite the potential for prolonged or accidental exposure to PA in industrial settings, the toxicity potential of PA was not well characterized. To address the knowledge gaps relevant to the toxicity profile of PA, the National Toxicology Program (NTP) conducted 2-week, 14-week and 2-year studies in male and female F344/N rats and B6C3F1/N mice. For the 2-week inhalation study, the rats and mice were exposed to 0, 31.3, 62.5, 125, 250 or 500 ppm. Significant mortality was observed in both rats and mice exposed to ≥125 ppm of PA. The major target organ of toxicity in both mice and rats was the liver with exposure-related histopathological changes (250 and 500 ppm). Based on the decreased survival in the 2-week study, the rats and mice were exposed to 0, 4, 8, 16, 32 or 64 ppm of PA in the 14-week study. No treatment-related mortality was observed. Mean body weights of male (≥8 ppm) and female mice (32 and 64 ppm) were significantly decreased (7–16%). Histopathological changes were noted in the nasal cavity, and included suppurative inflammation, squamous metaplasia, hyaline droplet accumulation, olfactory epithelium atrophy, and necrosis. In the 2-year inhalation studies, the rats were exposed to 0, 16, 32 and 64 ppm of PA and the mice were exposed to 0, 8, 16 and 32 ppm of PA. Survival of male rats was significantly reduced (32 and 64 ppm). Mean body weights of 64 ppm male rats were significantly decreased relative to the controls. Both mice and rats showed a spectrum of non-neoplastic changes in the nose. Increased neoplastic incidences of nasal respiratory/transitional epithelial adenoma were observed in both rats and mice. The incidence of mononuclear cell leukemia was significantly increased in male rats and was considered to be treatment-related. In conclusion, the key findings from this study indicated that the nose was the primary target organ of toxicity for PA. Long term inhalation exposure to PA led to nonneoplastic changes in the nose, and increased incidences of respiratory/transitional epithelial adenomas in both mice and rats. Increased incidences of harderian gland adenoma may also have been related to exposure to PA in male mice.     

Assessment of the genotoxic and carcinogenic risks of p-nitrophenol when it is present as an impurity in a drug product

According to the 2008 US FDA (draft) and 2006 EMEA guidance documents for genotoxic impurities, an impurity that is positive in an in vitro genotoxicity study, in the absence of in vivo genotoxicity or carcinogenicity data, should be treated as genotoxic and typically controlled to 1.5 μg/day for chronic use. For p-nitrophenol (PNP), existing study results (i.e., positive in vitro clastogenicity in mammalian cells, no information on its in vivo genotoxicity, and negative with respect to carcinogenicity in a dermal mouse study with no confirmation of systemic exposure) indicated that it should be considered genotoxic and exposure as a drug impurity limited. Therefore, to more completely characterize the genotoxic potential of PNP (consistent with the guidance documents), in vivo mouse micronucleus and dermal pharmacokinetic bridging studies were conducted. In the micronucleus study, PNP was negative, demonstrating that the reported in vitro clastogenicity is not present in vivo. In the pharmacokinetic study, PNP was well absorbed dermally, validating the negative dermal carcinogenicity assessment. These results indicate that PNP should be considered a non-genotoxic impurity and, as a drug impurity, a threshold limit of 4 mg/day would be set (per ICH Q3C). This threshold limit is higher than the EPA reference dose (listed in the 2006 Edition of the Drinking Water Standards and Health Advisories), so if present at such levels, the specification limits for PNP should be determined on a case-by-case basis, based on risk-benefit.     

The relationship between smoking machine derived tar yields and biomarkers of exposure in adult cigarette smokers in the US

Comprehensive data on human exposure to smoke constituents from different machine-measured tar yield cigarettes is limited. Methods: This study used a stratified, cross-sectional, multi-center design to estimate biomarkers of exposure (BOE) from nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), pyrene, CO, acrolein, and 1,3-butadiene and their relationship to tar yield categories of cigarette in adult smokers in the U.S. 3625 adults smokers were enrolled into four tar categories 2.9 mg (T1), 3.0–6.9 mg (T2), 7.0–12.9 mg (T3), and 13.0 mg (T4). Biomarkers were measured in blood (carboxyhemoglobin, 4-aminobiphenyl-hemoglobin (4-ABP-Hb)-adducts, serum cotinine) and 24 h urine (nicotine and five metabolites, calculated as nicotine equivalents (NE), NNAL, 1-OH-pyrene, 3-HPMA, MHBMA and DHBMA). Data were analyzed using analysis of covariance (ANCOVA). Results: Tar was a significant factor for most biomarkers in the ANCOVA models. The largest least square mean differences between tar categories was 35% for NE per day, 28% for NE per cigarette, 36% for serum cotinine, 42% for NNAL per day, 29% for NNAL per cigarette, 26% for 1-OHP, 24% for COHb, 14% for 3-HPMA and 40% for 4-ABP-Hb. Variability in BOE ranged from 41% to 154% CV. Conclusions: There was a statistically significant effect of machine-measured tar yield on most BOE, which were generally lower with lower tar yield.     

Effects of chronic n-hexane exposure on nervous system-specific and muscle-specific proteins

Two kinds of nervous system-specific and muscle-specific proteins, enolase and S-100 protein, were quantitatively determined in peripheral nerves and skeletal muscles of rats chronically exposed to a neurotoxic solvent — n-hexane. Three groups of animals were exposed to n-hexane vapor at three different solvent concentrations (500 ppm, 1200 ppm, 3000 ppm) for 12 h/day, 7 days/ week for 16 weeks. The body weight gain and motor nerve conduction velocity (MCV) in exposure groups show progressively concentration-dependent decreases compared to control values. Histopathological examination also demonstrates the degeneration of peripheral nerves in 3000 ppm- and 1200 ppm-exposed rats. The significant decrease in the amount of S-100 protein in peripheral nerves was observed not only in the high level exposure groups (3000 ppm and 1200 ppm), but also in the lowest level group (500 ppm), although the MCV and morphological examination remained unchanged at this level. In addition, the muscle-specific S-100 protein in 3000 ppm exposed rats' soleus also displayed a significant reduction. In contrast to this, however, enolase isozymes were not significantly changed by either dosage level in both nervous tissue and skeletal muscle. The experiment suggests that -and -S-100 proteins which are specifically localized in nervous system and muscles, respectively, are more vulnerable than enolase isozymes under treatment with n-hexane, and may possibly serve as a specific indicator to evaluate the neurotoxic effects. Further research would be worthwhile to elucidate the role of the specific S-100 protein in evaluating the neurologic damage induced by various industrial chemicals.     

Subchronic,reproductive, and maternal toxicity studies with tertiary butyl acetate (TBAC)

Tertiary-butyl acetate (TBAC) was tested for subchronic toxicity in rats and mice and reproductive toxicity in rats at inhalation concentrations of 0, 100, 400 or 1600 ppm. An oral maternal toxicity study was conducted in rats at dose levels of 0, 400, 800, 1000 and 1600 mg kg⁻¹ d⁻¹. In the inhalation studies, hematology, clinical chemistry, urinalysis, gross pathology and the majority of body weight and feed consumption values were unaffected. Exposure to TBAC at concentrations of 400 ppm and higher caused transient hyperactivity in mice and some evidence of increased motor activity counts in male rats at the 1600 ppm exposure level. TBAC caused α₂u-globulin accumulation in male rat kidneys from all exposure groups and increased liver weights in 1600 ppm rats and mice. Levels of thyroxin were decreased in male mice exposed to 1600 ppm TBAC for 4 weeks but otherwise thyroid endpoints were unaffected in rats and mice at either the 4 or 13 weeks time points. There was no evidence or immunotoxicity or reproductive toxicity in rats. Pregnant rats receiving 1000 mg kg⁻¹ d⁻¹ TBAC exhibited severe signs of acute neurotoxicity and decreased feed consumption and body weight gain. Fetal viability and growth were unaffected.     

Inhalation Toxicity of Sulfuryl Fluoride in Rats and Rabbits

Inhalation Toxicity of Sulfuryl fluoride in Rats and Rabbits.EISENBRANDT, D. L., AND NITSCHKE, K. D. (1989). Fundam Appl.Toxicol 12, 540–557. The inhalation toxicity of the structuralfumigant sulfuryl fluoride (SO₂F₂) was evaluated in rats andrabbits. Exposures for a preliminary 2-week study were 6 hr/day,5 days/week, to 0, 100, 300, or 600 ppm SO₂F₂ Nine often ratsat 600 ppm died or were moribund between the second and sixthexposures. Extensive kidney lesions were present in all ratsexposed to 600 ppm, whereas only minimal renal changes werenoted in rats at 300 ppm. Upper and lower respiratory tissueswere inflamed in the single rat that survived the 2-week exposureto 600 ppm. Rabbits exposed to 600 ppm SO₂F₂ were hyperactiveand one animal had a convulsion. Exposure to 300 or 600 ppmfor 2 weeks resulted in vacuolation and/or malacia in the cerebrumof all rabbits and most of these rabbits also had moderate inflammationof nasal tissues; a few rabbits at 600 ppm had inflammationof the trachea or bronchi. A subsequent 13-week study evaluatedrats and rabbits exposed to 0, 30, 100, or 300 ppm SO₂F₂ (337ppm TWA for rabbits). Rabbits initially were exposed to a highconcentration of 600 ppm; however, convulsions were noted intwo animals after nine exposures and the concentration subsequentlywas reduced to 300 ppm. Vacuolation and/or malacia were observedin the cerebrum of all rabbits at the highest concentration;one rabbit exposed to 100 ppm also had cerebral vacuolation.Rabbits at the highest concentration, as well as one rabbitexposed to 100 ppm, had inflammation of the nasal tissues. Ratsexposed to 300 ppm SO₂F₂ for 13 weeks had mottled incisor teeth,minimal renal effects, pulmonary histiocytosis, inflamma tionof nasal tissues, and cerebral vacuolation. Also, rats exposedto 100 ppm SO₂F₂ for 13 weeks had mottled teeth. fluoride toxicitywas suggested by mottled teeth in rats as well as elevationof serum fluoride levels in rats and rabbits exposed to SO₂F₂for 13 weeks. Although repeated exposure of rats and rabbitsto 100–600 ppm SO₂F₂ resulted in toxicity ofthe kidneys(rats only), brain, and respiratory system, no effects weredetected in animals exposed to 30 ppm for 13 weeks.     

Evaluation of subchronic toxicity of n-butyl acetate vapor.

The subchronic toxicity of n-butyl acetate (nBA), a common industrial solvent, was tested in rats in a 13-week inhalation study. Male and female Sprague-Dawley (SD) rats were exposed to concentrations of 0, 500, 1500 or 3000 ppm nBA for 6 h per day, 5 days per week for 13 consecutive weeks. Transient signs of sedation were observed only during exposure to the 1500 and 3000 ppm concentrations. Body weights for the 1500 and 3000 ppm groups were significantly reduced. Feed consumption values for the 1500 and 3000 ppm groups were significantly lower than the control group. Weights of the liver, kidneys and spleen were significantly lower for the 3000 ppm male group; testes and adrenal gland weights for the 1500 and 3000 ppm groups and the lung weight for the 3000 ppm male group were significantly higher than for the control group. Signs of irritation of the glandular stomach and necrosis in the non-glandular stomach were observed in 3000 ppm female rats. Degeneration of the olfactory epithelium along the dorsal medial meatus and ethmoturbinates of the nasal passages of some 1500 and all 3000 ppm rats was also seen. The severity was mild to moderate for the 3000 ppm group and minimal to mild for the 1500 ppm group. No effects were observed in the lungs of any group. The no-observed-effect level (NOEL) for this study is considered to be 500 ppm. The data presented here are relevant to the toxicity risk assessment of n-butanol due to the rapid hydrolysis of nBA in vivo.     

Early signs of oral and inhalative cadmium uptake in rats

Female wistar rats, 170–190 g, were exposed for 90 days to cadmium oxide aerosols containing 25 and 50 g Cd/m³ and for 63 days to 100 g Cd/m³. Simultaneously female wistar rats, 170–190 g, were fed 25, 50, and 100 ppm cadmium in drinking water for 90 days. After inhalation and ingestion of the metal, there were comparable kidney cadmium levels, but higher liver and blood levels after oral uptake. Coincident with the higher blood cadmium concentrations, proteinuria was observed only after oral administration. Likewise, there was a significant decrease of serum iron after ingestion and no lowering of the serum iron after inhalation of the metal. The inhalation led to a marked dose dependent weight increase of the lungs, which was followed by an impairment of gas exchange. Obviously, after inhalative cadmium uptake of 90 days pulmonary changes precede renal damage.     

Acute, Subchronic, and Developmental Toxicity and Genotoxicity of 1,1,1-Trifluoroethane (HFC-143a)

The toxicity potential of 1,1,1-trifluoroethane (HFC-143a),a CFC alternative, was evaluated in several acute, subchronic,and developmental toxicity studies by the inhalation route andin genotoxicity studies. HFC-143a has a very low acute inhalationtoxicity potential as shown by a 4-hr LC50 of >540,000 ppmin rats. HFC-143a has a low potential to induce cardiac sensitizationin experimental screening studies in dogs; only the highestconcentration tested—300,000 ppm—elicited a cardiacsensitization response. In an initial 4-week nose-only inhalationstudy, male and female rats were exposed 6 hr/day, 5 days/weekat concentrations of 0, 2000, 10,000, or 40,000 ppm. Femalesshowed no evidence of toxicity at any exposure level; male ratsdid exhibit degenerative changes only in the testes at all exposurelevels. However, because of exposure system irregularities,which resulted in excessive temperature conditions and stressin the HFC-143a-exposed groups, the study was repeated in malerats exposed by whole-body inhalation. In this repeat studyno toxicity was observed at 40,000 ppm. Moreover, a subsequent90-day whole-body inhalation study in rats exposed 6 hr/day,5 days/week at 0, 2000, 10,000, or 40,000 ppm resulted in noevidence of toxicity at any exposure concentration. The resultsof the second 4-week and the 90-day studies using whole-bodyexposures indicate that the findings from the first 4-week studywere related to the stress induced by excessive temperaturesand nose-only restraint. Therefore, the no-observed-effect level(NOEL) for rats repeatedly exposed up to 90 days was consideredto be 40,000 ppm. In developmental toxicity studies with ratsand rabbits, an increase in visceral variations or skeletalmalformations was observed, respectively, at HFC-143a concentrationsof 2000, 10,000, or 40,000 ppm (rat) or at the low and highconcentrations (rabbit). Because of the unusually low controlincidence of variations (1.6% per litter in the control versus6.8–16.8% for historical control values), the lack ofa clear dose-response relationship, and the lack of other developmentaleffects, these findings were not considered related to HFC-143aexposure. In adition, results from genotoxicity studies (Ames,chromosomal aberration with human lymphocytes, mouse micronucleus)demonstrated that HFC-143a Was not mutagenic.     

A 13-week subchronic oral toxicity study of l-serine in rats

A subchronic oral toxicity study was conducted to evaluate the safety of l-serine in Sprague–Dawley rats. The test article was administered once daily by gavage in male and female rats at dose levels of 0, 500, 1500, and 3000 mg/kg body weight/day for 13 weeks. Daily clinical signs, body weight, and food consumption were not affected by ingestion of the test article. There were no treatment-related adverse effects on urinalysis, hematology, serum biochemistry, organ weights, gross and histopathological examination. It was concluded that the no-observed-effect level (NOEL) for l-serine was 3000 mg/kg bw/day for both genders.     

Evaluation of subchronic inhalation toxicity of dimethyl disulfide in rats

This study was carried out to investigate the potential subchronic inhalation toxicity of dimethyl disulfide (DMDS) via whole-body exposure in F344 rats. Groups of 10 rats of each sex were exposed to DMDS vapor by whole-body exposure at concentrations of 0, 5, 25, or 125 ppm for 6 h/day, 5 days/wk for 13 wk. All the rats were sacrificed at the end of treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were examined. At 25 ppm, a decrease in the body weight gain, food intake, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and blood urea nitrogen (BUN) was observed in the males, but not in the females. However, at 125 ppm, a decrease in the body weight gain, food intake, and thymus weight and an increase in the weights of adrenal glands were observed in both genders. Serum biochemical investigations revealed a decrease in the AST, ALT, BUN, creatine phosphokinase (CPK), and triglyceride levels and an increase in the glucose level. In contrast, no treatment-related effects were observed in the 5 ppm group. The toxic potency of DMDS was slightly higher in males than that in females. In these experimental conditions, the target organ was not determined in rats. The no-observed-adverse-effect concentration (NOAEC) was found to be 5 ppm, 6 h/day for male rats and 25 ppm, 6 h/day for female rats.     

Evaluation of Subchronic Inhalation Toxicity of Dimethyl Disulfide in Rats

This study was carried out to investigate the potential subchronic inhalation toxicity of dimethyl disulfide (DMDS) via whole-body exposure in F344 rats. Groups of 10 rats of each sex were exposed to DMDS vapor by whole-body exposure at concentrations of 0, 5, 25, or 125 ppm for 6 h/day, 5 days/wk for 13 wk. All the rats were sacrificed at the end of treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were examined. At 25 ppm, a decrease in the body weight gain, food intake, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and blood urea nitrogen (BUN) was observed in the males, but not in the females. However, at 125 ppm, a decrease in the body weight gain, food intake, and thymus weight and an increase in the weights of adrenal glands were observed in both genders. Serum biochemical investigations revealed a decrease in the AST, ALT, BUN, creatine phosphokinase (CPK), and triglyceride levels and an increase in the glucose level. In contrast, no treatment-related effects were observed in the 5 ppm group. The toxic potency of DMDS was slightly higher in males than that in females. In these experimental conditions, the target organ was not determined in rats. The no-observed-adverse-effect concentration (NOAEC) was found to be 5 ppm, 6 h/day for male rats and 25 ppm, 6 h/day for female rats.     

Inhalation Toxicity of Butylene Oxide

Inhalation Toxicity of Butylene Oxide. Miller, R.R., Quast,J.R., Ayres, J.A. and McKenna, M.J. (1981). Fundam. Appl. Toxicol.1:319–324. Exposure of male and female Fischer 344 ratsand B6C3F1 mice to 0,400,800 or 1600 ppm butylene oxide vapors6 hours per day, 5 days per week, for a total of 9 days duringa 2-week interval revealed a definite species difference insensitivity to these high concentrations of the test material.All mice in the 1600 ppm group were dead prior to the 3rd dayof exposure while all rats exposed to 1600 ppm survived untilscheduled sacrifice with no obvious signs of distress exceptfor a pronounced retardation of growth. Inflammatory and degenerativechanges in the nasal mucosa were detected histopath-ologicallyin rats in the 1600 ppm group. Myeloid hyperpla-sia in the bonemarrow, and elevated mean white blood cell counts for male andfemale rats in the 1600 ppm group may possibly have been relatedto the inflammatory nasal lesions or to generalized stress.A subchronic inhalation toxicity study in which Fischer 344rats and B6C3F1 mice were exposed to 0,75,150 or 600 ppm for13-weeks resulted in no treatment-related mortalities. Slightgrowth retardation, particularly for female rats and mice, wasapparent for animals in the 600 ppm group. Histopathologic examinationsrevealed treatment-related lesions of the nasal mucosa in bothrats and mice in the 600 ppm group. There were no histopathologicobservations in rats or mice in the 75 or 150 ppm groups whichwere considered to be related to exposure to the test material.     

Two-year inhalation study of carcinogenicity and chronic toxicity of 1,4-dioxane in male rats

Carcinogenicity and chronic toxicity of 1,4-dioxane were examined by inhalation exposure of 50 male F344 rats to 1,4-dioxane vapor at 0 (clean air), 50, 250, or 1250 ppm (v/v) for 6 h/day, 5 days/wk, and 104 wk. Survival rates of 250 and 1250 ppm-exposed groups were decreased near the end of the 2-yr exposure period, due probably to the occurrence of malignant tumors. A statistically significant but marginal decrement of terminal body weight (<10%) was found in the 1250 ppm-exposed group, suggesting slight systemic toxicity. Significant changes in plasma levels of AST, ALT, ALP, and γ-GTP and relative weight of the liver occurred in the 1250 ppm-exposed group. Dose-dependent and statistically significant increases in incidences of nasal squamous cell carcinomas, hepatocellular adenomas, and peritoneal mesotheliomas were found primarily in the 1250 ppm-exposed group. The incidences of renal cell carcinomas, fibroadenomas in the mammary gland, and adenomas in the Zymbal gland were also increased dose-dependently. Preneoplastic lesions occurred in the nasal cavity and liver of the 1,4-dioxane-exposed groups. As nonneoplastic lesions, the significantly increased incidences of nuclear enlargement, atrophy, and respiratory metaplasia in the nasal cavity were noted at 50 ppm and above. A LOAEL (lowest observed adverse effect level) was determined at 50 ppm for the nasal endpoint of general chronic toxicity. This study provides clear evidence of carcinogenicity for 1,4-dioxane in male rats. A cytotoxic-proliferative and in vivo genotoxic mode of action is suggested to operate in 1,4-dioxane-induced carcinogenesis.     

The protective potential of <Emphasis Type="Italic">Yucca schidigera</Emphasis> (Sarsaponin 30<Superscript>®</Superscript>) against nitrite-induced oxidative stress in rats

The present study was designed to determine the protective effects of Yucca schidigera (Ys) against oxidative damage induced by acute nitrite intoxication as well as the histopathological evaluation of Ys in rats. The rats were divided into three groups each containing 12 rats: control (C); nitrite intoxication (N); Ys + nitrite intoxication (NY). C and N groups were fed standard rat feed (SRF). The NY group was fed SRF + 100 ppm Ys powder for 4 weeks. Acute nitrite intoxication was induced by subcutaneous (s.c.) administration of sodium nitrite (60 mg/kg) 1 day after the feeding period. Fifty minutes after sodium nitrite administration, blood samples and tissues including lung, liver, and kidney were collected for clinical biochemistry and histopathological investigations. Ys treatment was found to decrease methemoglobin, blood and tissue malondialdehyde, and tissue nitric oxide concentrations, and to increase the glutathione in blood and various tissues. However, plasma nitric oxide, total antioxidant activity, β-carotene, and vitamin A did not differ between N and NY groups. While the N group rats showed distinct pathology in various tissues (compared with controls), the NY group had similar lung and liver pathology to the control. Only moderate or mild hemorrhage and hyperemia were seen in kidneys of NY group rats. Consequently, the natural compounds found in Ys, such as polyphenols, steroidal saponins, and other phytonutrients, could be used to substantially protect the organism from nitrite-induced oxidative damage and its complications.     

Subchronic toxicity study of water pepper extract in F344 rats.

A subchronic toxicity study of water pepper extract (WPE) from Polygonum hydropiper L. was conducted in groups of 10 male and 10 female F344 rats fed powdered diets containing 0, 62.5, 250, 1000 or 4000 ppm concentrations for 13 weeks. Suppression of body weight gain due to decreased food consumption was observed in both sexes at 4000 ppm, and at autopsy, increase of relative weights was observed for the brain, liver, spleen, kidneys, and testes in these animals, suggestive of the reflection of the reduced body weights. At this dose, slight increases of blood urea nitrogen in both sexes and serum alanine aminotransferase, Na and Cl in females, were observed, suggestive of weak hepatic and renal toxicity, at least in females. The same females also exhibited slight decrease of red blood cells and haematocrit, slight increase of mean corpuscular volume and mean corpuscular haemoglobin, and minimal increase of splenic haemosiderin deposition, providing evidence of slight haemolytic anemia. On the other hand, enhanced accumulation of mast cells was observed in the mesenteric lymph nodes at 4000 ppm in males and 1000 and 4000 ppm in females. Considering the anti-anaphylactic properties of polygodial, a major constituent of WPE, the mast cell accumulation was concluded to be an adaptive change in response to the subchronic oral administration of WPE. Based on the present toxicity data, 1000 ppm was determined to be the no-observed-adverse-effect level, translating into 57.4 and 62.9 mg/kg/day for male and female rats, respectively.     

Short-term inhalation toxicity studies with peroxyacetyl nitrate in rats

The inhalation toxicity of peroxyacetyl nitrate (PAN) was examined in acute (single exposure), sub-acute (4-week repeated exposure) and subchronic (13-week repeated exposure) studies in rats. The 4-h LC₅₀ was found to be 95 ppm.In the 4-week study rats were exposed to 0, 0.9, 4.1 or 11.8 ppm PAN vapour for 6 h/day, 5 days/week. Exposure to 11.8 ppm caused abnormal behaviour, growth retardation, mortality, elevated haemoglobin contents, haematocrit values and erythrocyte counts, increased lung weights and severe inflammatory changes and epithelial hyper- and metaplasia in the respiratory tract. At 4.1 ppm minimal behavioral disturbance, transient growth depression, slightly increased lung weights and mild histopathological changes in the respiratory tract were found. At 0.9 ppm no treatment-related alterations were detected.In the 13-week study rats were exposed to 0, 0.2, 1.0 or 4.6 ppm PAN vapour for 6.5 h/day, 5 days.week. Exposure to 4.6 ppm resulted in changes similar to those found at 11.8 ppm in the 4-week experiment, but no mortality occurred. At 1.0 ppm minimal irritation of the mucous membranes in the nasal cavity was the only PAN-related effect observed. No treatment- related changes were seen at 0.2 ppm. It was concluded that the no-toxic- effect level is between 0.2 and 1.0 ppm, and very probably close to the upper value.     

Metabolomics as read-across tool: A case study with phenoxy herbicides

New technologies, such as metabolomics, can address chemical grouping and read across from a biological perspective. In a virtual case study, we selected MCPP as target substance and MCPA and 2,4-DP as source substances with the goal to waive a 90-day study with MCPP. In order to develop a convincing case to show how biological data can substantiate read across, we used metabolomics on blood samples from the 28-day studies to show the qualitative and quantitative similarity of the substances. The 28-day metabolome evaluation of source substances and the target substance indicate liver and kidneys as target organs. 2,4-DP was identified as the best source substance. Using the information of the 90-day 2,4-DP study, we predicted MCPP's toxicity profile at 2500 ppm: reduced food consumption and body weight gain, liver and kidney weight increases with clinical-pathology changes and a moderate red blood cell parameter reduction. NOEL prediction for MCPP was below that of 2,4-DP (<500 ppm), and similar to that of MCPA (≥150 ppm). Qualitatively, these predictions are comparable to the results of the real MCPP 90-day study in rats (reduced food consumption and body weight gain, weight increases and clinical-pathology changes in liver and kidneys, reduced red blood cells values). Quantitatively, the predicted NOAEL (150 ppm) is similar to the actual study (NOEL = 75 ppm, NOAEL ≤ 500 ppm). Thus, the 90-day rat toxicity study of MCPP could have been waived and substituted by the 90-day results of 2,4-DP by using metabolome data of 28 day studies.