Search

This study was designed to investigate the harmful effects of toluene inhalation in the liver of rats and possible protective effects of melatonin on these detrimental effects. For this purpose, 21 adult male Wistar-albino rats were randomly divided into three equal groups. Animals in group I were used as control. The rats in group II were exposed to toluene (3000 ppm/1 hour/day) for 4 weeks, while the rats in group III were treated with melatonin (10 mg/kg/day, intraperitoneally [ip]) plus toluene inhalation. At the end of the experimental period, liver and blood samples were taken from the decapitated animals. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total bilirubin and albumin levels were determined. Liver tissue sections were stained with routine histological methods and examined under the light microscope. In addition, the sections were immunohistochemically stained using avidin-biotin-peroxidase method for determination of apoptosis. The liver tissue activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and malondialdehyde (MDA) levels were also measured. Toluene inhalation significantly increased serum ALT, AST and tissue MDA, and decreased serum albumin, but did not affect serum ALP, total bilirubin levels and tissue SOD, GSH-Px and CAT activity when compared with controls. The increases in tissue MDA and serum ALT and AST levels induced by toluene inhalation were significantly inhibited by melatonin treatment. In light microscopic observations of tissues from toluene-inhaled rats, massive hepatocyte degeneration, ballooning degeneration and mild pericentral fibrosis were observed. Bax immune reactivity was also increased significantly. Melatonin treatment decreased the balloon degeneration, fibrosis and Bax immune reactivity in the liver of toluene-inhaled rats. In view of the present findings, it is suggested that melatonin has hepatoprotective effects against toluene toxicity via primarily antioxidative properties.

Effects of chronic exposure to n-hexane and toluene on some nerve-specific marker proteins in rat central nervous system (CNS) and peripheral nervous system (PNS) were assessed and compared. The rats were exposed to 2000 ppm n-hexane, 12 hr/day, 6 days/week, for 24 weeks, and to 1000 ppm toluene, 8 hr/day, 6 days/week, for 16 weeks. The level of neuron-specific enolase (NSE), creatine kinase-B (CK-B), and beta-S100 protein in cortex, cerebellum, spinal cord, and proximal and distal sciatic nerve was determined by enzyme immunoassay method. In n-hexane-exposed rats, the level of NSE, CK-B, and beta-S100 decreased significantly in the distal segment of the sciatic nerve, while the marker proteins in CNS and proximal sciatic nerve remained unchanged. In contrast, chronic exposure to toluene mostly affected these marker proteins in CNS tissues, displaying the increase of NSE, CK-B, beta-S100 in cerebellum, as well as the increase of beta-S100 in spinal cord. No quantitative changes of the three proteins in distal sciatic nerve were observed after exposure to toluene. n-Hexane-induced peripheral distal neuropathy and toluene-induced brain gliosis appeared to be responsible for this different pattern of biochemical changes. The present study suggests the usefulness of using these nerve-specific marker proteins to assess the solvent-related CNS and PNS neurotoxicity.

Changes in Lys- and Leu-aminopeplidase activities in several brain regions of the rat, after acute toluene administration, are described in this research. Aminopeptidase activity has been suggested as a candidate regulator of the degradation of several neuroactive peptides. Lys-aminopeptidase activity was significantly decreased in the thalamus, amygdala, and medulla oblongata. Leu-aminopeptidase activity was significantly decreased in the thalamus and cerebellum. It is suggested that these aminopeptidase activities could play a part in the mechanism of toluene neurotoxicity.

The in vivo dose-response relationship between toluene and reactive oxygen species (ROS) formation in rat brain, liver, kidney, and lung, and the time-course of these effects has been characterized. The rate of oxygen radical formation was measured using the probe 2',7'-dichlorofluorescin diacetate. In vivo exposure to various doses of toluene (0.5, 1.0, and 1.5 g/kg ip) elicited a dose-dependent elevation of ROS generation within crude mitochondrial fractions obtained from rat lung and kidney, and within crude synaptosomal fractions from cerebellum. ROS formation in crude mitochondrial fractions from liver, and crude synaptosomal fractions from striatum and hippocampus, reached a maximum value at relatively low doses of toluene. Of the brain regions, the hippocampus had the highest induced levels of ROS. In vivo exposure to a single dose of toluene (1.5 g/kg ip), revealed that toluene-induced ROS reached a peak within 2 h, which correlated directly with measured toluene blood levels. This elevated oxidative activity was maintained throughout the next 24 h, even though blood values of toluene decreased to negligible amounts. These results demonstrate that exposure to toluene results in broad systemic elevation in the normal rate of oxygen radical generation, with such effects persisting in the tissues despite a rapid decline in toluene blood levels. Acute exposure to toluene may lead to extended ROS-related changes, and this may account for some of the clinical observations made in chronic toluene abusers.

The effects of subchronic inhalation exposure to toluene (80 ppm, for 4 weeks, 5 days/week, 6 h/day) was studied on spatial learning (postexposure days 3-6) and memory (postexposure day 14) using a water maze, on spontaneous and apomorphine-induced (1 mg/kg, subcutaneously (s.c.)) locomotor activity (postexposure day 17) and on the binding parameters of the dopamine D2 agonist S(-)[N-propyl-3H(N)]propylnorapomorphine ([H]NPA) in membrane preparations of the neostriatum of the rat. Toluene treatment was found to cause a statistically significant impairment in acquisition and retention of the spatial learning task. Furthermore, toluene significantly increased (2-fold) apomorphine-induced locomotion and caused a trend for a 50-60% increase in motility without any significant effect on rearing. Spontaneous locomotion, motility and rearing were not affected by toluene. Toluene treatment produced a significant 30-40% increase in the Bmax values of [3H]NPA and a trend for a 20-30% increase in the KD values. These results indicate that subchronic exposure to toluene in low concentrations causes a slight but persistent deficit in spatial learning and memory, a persistent increase in dopamine-mediated locomotor activity and an increase in the number of dopamine D2 receptors in the rat.

The aim of this study was designed to evaluate the possible protective effects of thymoquinone (TQ) on the neuronal injury in the frontal cortex after chronic toluene exposure in rats. The rats were randomly allotted into one of three experimental groups: A (control), B (toluene treated) and C (toluene treated with TQ); each group contain 10 animals. Control group received 1 ml normal saline solution and toluene treatment was performed by inhalation of 3,000 ppm toluene, in a 8 h/day and 6 day/week order for 12 weeks. The rats in TQ treated group was given TQ (50 mg/kg body weight) once a day orally for 12 weeks starting just after toluene exposure. Tissue samples were obtained for histopathological investigation. To date, no histopathological changes of neurodegeneration in the frontal cortex after chronic toluene exposure in rats by TQ treatment have been reported. In this study, the morphology of neurons in the TQ treatment group was well protected. Chronic toluene exposure caused severe degenerative changes, shrunken cytoplasma, severely dilated cisternae of endoplasmic reticulum, markedly swollen mitochondria with degenerated cristae and nuclear membrane breakdown with chromatin disorganization in neurons of the frontal cortex. We conclude that TQ therapy causes morphologic improvement on neurodegeneration in frontal cortex after chronic toluene exposure in rats. We believe that further preclinical research into the utility of TQ may indicate its usefulness as a potential treatment on neurodegeneration after chronic toluene exposure in rats.

Monocyclic aromatic hydrocarbons (MAHs) such as benzene, toluene and xylene are being extensively used for various industrial and household purposes. Exposure to these hydrocarbons, occupationally or non-occupationally, is harmful to organisms including human. Several studies tested for toxicity of benzene, toluene and xylene, and interestingly, only a few studies looked into the attenuation. We used Drosophila model to test the genotoxic and apoptotic potential of these compounds and subsequently evaluated the efficiency of two phytochemicals, namely, quercetin and curcumin in attenuating test chemical induced toxicity. We exposed third instar larvae of wild type Drosophila melanogaster (Oregon R+) to 1.0-100.0 mM benzene, toluene or xylene, individually, for 12, 24 and 48 h and examined their apoptotic and genotoxic potential. We observed significantly (P

Toluene is an organic solvent that is widely used by industry and is ubiquitous in our environment. As a result, exposure to solvents like toluene in work-related settings (i.e., relatively constant, low-level exposures) or through inhalant abuse (i.e., relatively intermittent, high-level exposures) is increasing for many women of reproductive age. Evidence suggests that the risk for pregnancy problems, as well as developmental delays and neurobehavioral difficulties, is higher for the children of women who have been exposed to high concentrations of organic solvents during pregnancy than for those who have not. These risks appear to be higher in cases of abuse exposure to solvents such as toluene, particularly in comparison to the risk for teratogenic outcomes with occupational solvent exposure. Despite this, the reproductive toxicology and teratology following abuse of toluene and other inhalants remains under-investigated. This brief review describes the current state of our understanding of the reproductive and teratogenic risk of gestational toluene abuse. The data to date suggest that the high levels of toluene exposure typical with inhalant abuse are more detrimental to fetal development than typical occupational exposure, and preclinical paradigms can be beneficial for investigating the processes and risks of prenatal solvent exposure. While substantial research has been done on the reproductive effects of occupational exposures to organic solvents, more research is needed on the outcomes and mechanisms of exposures typical of inhalant abuse.

Volatile organic compounds (VOCs) are reported to cause adverse effects on pulmonary function in occupationally exposed workers. However, evidence is lacking on the effect in the general population. We hypothesised that VOCs impair pulmonary function through enhancing oxidative stress, especially in the elderly population. A longitudinal panel study of 154 elderly people was performed in South Korea. Repeated spirometric tests were performed up to eight times on different days for each subject. We also measured urinary concentrations of metabolites of the VOC and markers of oxidative stress (malondialdehyde and 8-oxo-2'-deoxyguanosine) on the same day of spirometric tests. A mixed linear regression model was used to evaluate the association among the VOC metabolites, oxidative stress markers and spirometric tests. We found that the urinary levels of hippuric acid and methylhippuric acid, which are metabolites of toluene and xylene, respectively, were significantly associated with reduction of forced expiratory volume in 1 s (FEV₁), FEV₁/forced vital capacity (FVC), and forced expiratory flow at 25-75% of FVC. We also found significant associations between the metabolites of VOCs and the markers of oxidative stress. In addition, the oxidative stress markers were associated with pulmonary function parameters. This study suggests that exposure to toluene and xylene exert a harmful effect on pulmonary function by exacerbating oxidative stress in elderly people.

Prompted by reports of sexual impotence among chemical factory workers exposed to amsonic acid (4,4'-diaminostilbene-2,2'-disulfonic acid; CAS 81-11-8) and its synthetic precursors 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNSDSA; CAS 128-42-7), 2-methyl-5-nitrobenzenesulfonic acid (MNBSA; CAS 121-03-09), and 4-nitrotoluene (CAS 99-99-0), the uterine-weight-increasing actions of single intraperitoneal doses of these chemicals were determined at 24 h after treatment in weanling female rats and compared to the results of similar experiments with diethylstilbestrol (DES; CAS 56-53-01), a synthetic estrogen chemically related to amsonic acid and DNSDSA. Doses of 100 mg/kg or less of amsonic acid were either without effects or produced equivocal effects, while uterine weights were increased after doses of 300 and 1000 mg/kg; doses of 3000 mg/kg were clearly toxic. Neither DNSDSA nor MNBSA increased uterine weight after doses that were not overtly toxic. Doses of 10 mg/kg or less of 4-nitrotoluene were without effect, but doses of 30 and 100 mg/kg increased uterine weights without producing overt toxicity; doses of 1000 mg/kg were clearly toxic. While both amsonic acid and 4-nitrotoluene exhibited uterotropic effects, they were both much weaker than DES in this respect. Other experiments indicated that the time course of the effects of approximately equiactive doses of amsonic acid and DES were very similar, and that the responses to oral doses of amsonic acid were not appreciably different from the responses to the same doses given intraperitoneally. Finally, a sample of amsonic acid taken from the workplace of the complaining workers was also found to have uterotropic activity. These experiments suggest that amsonic acid and 4-nitrotoluene have estrogenic activity, and thus provide a possible mechanistic explanation for the complaints of impotency in factory workers exposed to these substances.

The aim of the present study was to investigate the effect of low-level concentrations, under the occupational acceptable limits, of toluene exposure and peptidoglycan (PGN) stimulation on Th1/Th2 immunity in infant mice. Pregnant BALB/c mice and their offspring were exposed to low-level toluene inhalation (0, 5, and 50 ppm) for 4 wk (from the late prenatal stage to early postnatal stage) in a whole-body exposure chamber. Some of the pregnant mice and their offspring were stimulated with PGN during toluene exposure. We measured total immunoglobulins of different subclasses in plasma, and production and expression level of cytokines in the lung and spleen, and transcription factors related to Th1/Th2 immunity in the spleen of infant (3 wk old) mice. Exposure of mice to 5 or 50 ppm toluene resulted in increased immunoglobulin (Ig) G1 and decreased IgG2a and IgE antibodies in the plasma; significantly decreased T-bet, GATA-3, and Foxp3 mRNA in the spleen; and a tendency toward decreased interferon (IFN)-gamma mRNA in spleen. Exposure of mice to low-level toluene together with PGN stimulation resulted in decreased IgG1 as well as IgG2a antibodies in the plasma and Foxp3 mRNA in spleen as compared with control or PGN-treated mice. These findings suggest that low-level toluene exposure and PGN stimulation from the late prenatal to early postnatal stage suppressed the splenic parameter related to Th1/Th2 immunity in infant mice.

Meta- and reanalyses of the available data for the neurobehavioral effects of acute inhalation exposure to toluene were reported by Benignus et al. The present study was designed to test the generality of the toluene results in as many other solvents as possible by further meta- and reanalyses. Sufficient data for meta-analyses were found for only four solvents; toluene, trichloroethylene, perchloroethylene, and 1,1,1-trichloroethane. The results for these solvents showed that rats were less affected by each of the solvents when they were tested in highly motivating situations, for example, rewarded for rapid or correct responding or escape from electrical shock, compared with less motivating circumstances. The four solvents did not differ significantly in potency on any outcome measure when dose was expressed as molar brain concentration. When tested in tasks with low-motivational contingencies, the dose-effect curves of humans (reaction times) and rats (electrophysiological responses to visual stimuli) were not significantly different. However, on an exploratory follow-up analysis, humans were less sensitive than rats. No human data were found to test whether species differed under strong motivation. Dose-equivalence curves were derived for extrapolating to human effects from rat data.

Inhalant abuse in young people is a growing public health concern. We reported previously that acute toluene intoxication in young rats, using a pattern of exposures that approximate abuse patterns of inhalant use in humans, significantly altered neurochemical measures in select brain regions. In this study, adolescent and young adult rats were exposed similarly to an acute (2 x 15 min), high dose (8000-12,000 ppm) of toluene and high-resolution magic angle spinning proton magnetic resonance spectroscopy (HR-MAS 1H-MRS) was used to assess neurochemical profiles of tissue samples from a number of brain regions collected immediately following solvent exposure. The current investigation focused on N-acetyl-aspartate (NAA), choline-containing compounds, creatine, glutamate, GABA, and glutamine. Contrary to our predictions, no significant alterations were found in the levels of NAA, choline, creatine, glutamate, or glutamine in adolescent animals. In contrast to these minimal effects in adolescents, binge toluene exposure altered several neurochemical parameters in young adult rats, including decreased levels of choline and GABA in the frontal cortex and striatum and lowered glutamine and NAA levels in the frontal cortex. One of the more robust findings was a wide-ranging increase in lactate after toluene exposure in adult animals, an effect not observed in adolescents. These age-dependent effects of toluene are distinct from those reported previously in juvenile rats and suggest a developmental difference in vulnerability to the effects of inhalants. Specifically, the results suggest that the neurochemical response to toluene in adolescents is attenuated compared to adults, and imply an association between these neurochemical differences and age-influenced differences in solvent abuse in humans.

Humans can come into contact with thinner by occupational exposure or by intentional inhalation abuse. Numerous studies of workers for genotoxic effects of thinner exposure have yielded conflicting results, perhaps because co-exposure to variable other compounds cannot be avoided in workplace exposure studies. In contrast, there is no data concerning the genotoxic effects of intentional inhalation abuse. The aim of this project was to examine the genotoxic effects of thinner inhalation in an animal model of thinner abuse (rats exposed to 3000 ppm toluene, a high solvent concentration over a very short, 15 min time period, twice a day for 6 weeks). The data presented here provides evidence that thinner inhalation in our experimental conditions is able to induce weight loss, lung abnormalities and oxidative stress. This oxidative stress induces oxidative DNA damage that is not a characteristic feature of genotoxic damage. No significant difference in DNA damage and DNA repair (biomarkers of genotoxicity) in lymphocytes from thinner-treated and control rats was found. Lead treatment was used as a positive control in these assays. Finally, bone marrow was evaluated as a biomarker of cellular alteration associated with thinner inhalation. The observed absence of hemopoietic and genetic toxicity could be explained in part by the absence of benzene, the only carcinogenic component of thinner; however, benzene is no longer a common component of thinner. In conclusion, thinner did not cause genotoxic effects in an experimental model of intentional abuse despite the fact that thinner inhalation induces oxidative stress.

The irreversible CNS effects of six months' exposure to toluene (0, 500, and 1500 p.p.m.) in rats was studied applying a multi-disciplinary approach. After an exposure-free period, neurobehavioural, morphometric, pathological, and biochemical examinations were performed. No neurobehavioural or gross pathological changes were found. Morphometric measurements did not show loss of neurones. At 500 p.p.m. the mean nuclear volume and mean perikaryonal volume and the variation of the values of these parameters was increased in the exposed groups compared to the controls. Noradrenaline (NA), dopamine (DA), and 5-hydroxytryptamine (5-HT) levels were significantly changed in various brain regions. It is concluded that this investigation failed to reveal overt toluene-induced CNS-neurotoxicity, however, certain irreversible effects were found which further add to the accumulating evidence of the chronic CNS-neurotoxicity of toluene.

The chronic abuse of the solvent toluene results in structural and functional impairment of various organs. However, the pathophysiological mechanisms that cause these impairments of function are not clearly understood. This study aims to assess the effect of chronic toluene exposure (15, 30 and 45 days) on the oxidative stress and antioxidant status of different organs in the rat. Also, cyclooxygenase-2 and caspase-3 activities (a marker of apoptosis) are studied. Forty male albino rats were used and divided into four groups: controls (group I) and three other groups receiving a single daily dose of toluene (650 mg/kg) for 15 days (group II), 30 days (group III) and 45 days (group IV). The animals were then sacrificed and the brain cortex, cerebellum, liver, kidney and testis were separated for the determination of thiobarbituric acid reactive substance (TBARS), GSH, glutathione disulphide (GSSG) and glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), superoxide dismutase (SOD), cyclooxygenase-2 (COX-2) and caspase-3 activity. Results showed a significant and time-dependent increase in the levels of TBARS, GSSG and in GST, SOD, COX-2 and caspase-3 activity, while GSH, GR and GPx showed a marked decline in most tissues. The brain (cortex and cerebellum) was the most affected organ, showing the greatest increase in one apoptotic marker (caspase-3), while the testis and kidneys were least affected. In conclusion, oxidative stress and derangement of the GSH:GSSG ratio, induced chronic inflammatory change and apoptosis may play an essential role in toluene toxicity

Introduction Toluene toxicity primarily affects central nervous system white matter, causing a characteristic brain MRI pattern. Case report A toluene addicted man, after an abstinence period and a treatment with neuroleptics, presented with severe worsening of preexisting generalized tremor, opsoclonus, dysarthria, gait inability, jerky tendon reflexes and behaviour disorders. Magnetic resonance imaging showed mild leukoencephalopathy and hypointensities in deep gray matter nuclei. The DaT-scan revealed a decrease in presynaptic dopamine reuptake. Conclusion Clinical and neuroradiological findings and the possible sensitivity to neuroleptics indicate dopaminergic impairment. Our case suggests that chronic toluene abuse causes presynaptic dopaminergic depletion.

Exposure to benzene, toluene and xylene in the human population may pose a health risk. We tested a working hypothesis that these test chemicals cause cellular toxicity to a non-target organism, Drosophila melanogaster. Third instar larvae of D. melanogaster transgenic for hsp70, hsp83 and hsp26 and Oregon R(+) strain were exposed to 1.0-100.0 mM benzene, toluene and xylene for 2-48 h to examine the heat shock proteins (hsps), ROS generation, anti-oxidant stress markers and developmental end points. The test chemicals elicited a concentration- and time-dependent significant (p0.01) induction of the hsps in the exposed organism in the order of hsp70hsp83or=hsp26 as evident by beta-galactosidase activity after 24 h. RT-PCR amplification studies in Oregon R(+) larvae revealed a similar induction pattern of these genes along with hsp60 in the order of hsp70hsp60hsp26or=hsp83. Under similar experimental conditions, a significant induction of ROS generation and oxidative stress markers viz. superoxide dismutase, catalase, glutathione S-transferase, thioredoxin reductase, glutathione, malondialdehyde and protein carbonyl content was observed. Sub-organismal response was propagated towards organismal response i.e., a delay in the emergence of flies and their reproductive performance. While hsp70 was predominantly induced in the organism till 24 h of treatment with the test chemicals, a significant or insignificant regression of Hsp70 after 48 h was concurrent with a significant induction (p0.01) of hsp60hsp83or=hsp26 in comparison to the former. A significant positive correlation was observed between ROS generation and these hsps in the exposed organism till 24 h and a negative correlation between ROS generation and hsp70 in them after 48 h indicating a modulatory role of ROS in the induction of hsps. The study suggests that among the tested hsps, hsp70 may be used as an early bioindicator of cellular toxicity against benzene, toluene and xylene and D. melanogaster as an alternative animal model for screening the risk posed by environmental chemicals.

Effects of toluene on the electroencephalogram (EEG) and its power spectra were measured during a 2-hr exposure in a dynamic inhalational chamber in young rats (30-53 days old) and compared to those in adult rats (63-77 days old). Rats were exposed to one of the three concentrations [low (108-111 ppm), medium (160-163 ppm), and high (407-432 ppm)] of toluene on different days. In tests on sleep-wake cycle, in the young animals the duration of the wake stage (W) was increased with decreases of rapid eye movement (REM) and non-REM (NREM) sleep during hr 1 and hr 2 of exposure to the low concentration. These effects were marked at the medium and the high concentrations. In adult rats, at the low concentration the increase of W and the decrease of REM were observed only at hr 1; however, at medium and high concentrations these changes of W and REM sleep were marked along with a decrease of NREM. Comparison of the changes of duration of different states in rats of two age groups showed that there was a significant difference in the increase of W and the decrease of NREM sleep in young rats at hr 2 of exposure to low concentrations only compared to those in adult rats. Tested on power spectrum in young rats during REM sleep recorded from the visual cortex, the power of delta waves increased at the medium and high concentrations and that of theta wave decreased at the high concentration during hr 2 of exposure compared to the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

An efficient method for the unbiased estimation of the total number of neurons in rat brain cortex is presented. The method is reasonable fast, the counting procedure takes 2-3 h per rat, and gives an estimate of the total neuron number in cortex cerebri with an CE of 0.10. The rat cerebral cortex is found to have a mean volume of 253 mm3 and to contain a mean of 21 million neurons. The method has been used in a neurotoxicologic study, in which rats were given toluene perorally in doses of 200, 400 and 800 mg/kg/day, respectively, for 12 weeks, followed by an exposure-free period of 4 weeks. The total number of neurons in rat brain cortex cerebri showed no significant difference between exposed and non-exposed animals. The applicability of the method is discussed.

While it is possible to establish the chemical composition of air pollutants through conventional air sampling and analytical techniques, such data do not provide direct measures of toxicity and the potential mechanisms that induce adverse effects. The aim of this study was to optimize in vitro methods for toxicity testing of airborne contaminants. An integrated approach was designed in which appropriate exposure techniques were developed. A diversified range of in vitro assays using multiple human cell systems were implemented. Direct exposure of cells to airborne contaminants was developed by culturing cells on porous membranes in conjunction with a horizontal diffusion chamber system. Concentration-response curves were generated allowing the measurement of toxicity endpoints. Regression analysis indicated a significant correlation between in vitro and published in vivo toxicity data for the majority of selected chemical contaminants. Airborne IC50 values were calculated for selected volatile organic compounds (xylene, 5350 +/- 328 ppm > toluene, 10,500 +/- 527 ppm) and gaseous contaminants (NO2, 11 +/- 3.54 ppm > SO2, 48 +/- 2.83 ppm and > NH3, 199 +/- 1.41 ppm). Results of this study indicate the significant potential of in vitro methods as an advanced technology for toxicity assessment of airborne contaminants.

Aims Inhalant abuse during pregnancy lowers birth weight and impedes early development. These studies explored the effects of brief, repeated, prenatal toluene exposures in pregnant female rats on body weight, metabolic rate, body composition, and food intake in their offspring. Method Rats were exposed to 0, 8000, 12,000, or 16,000 ppm of toluene twice daily for 15 min from gestational days 8 to 20. The effects of such exposures on post-weaning litter weights, oxygen consumption, carbon dioxide output, and body fat content were determined in 2 cohorts ( n = 23, n = 24) of offspring. Food intakes and weight changes in response to 3 different diets (regular chow, purified diet, purified high fat diet) were examined in another cohort ( n = 24) from postnatal days 72 to116. Results Litter weights showed a significant linear decrease as a function of toluene dose. Offspring exposed to the 16,000 ppm toluene dose displayed statistically lower energy expenditures than control rats. Male rats exposed to 8000 or 16,000 ppm toluene had significantly greater percentage of body fat as well as total body fat than the other groups. Toluene also significantly suppressed weight gain over the time chow was consumed compared to the 0 ppm control group. Finally there were trends for a main effect of toluene dose on food intake during chow and during high fat diet consumption, with rats in the 12,000 ppm group consuming more than the 0 ppm group on both diets. Discussion These data suggest that, in addition to other previously documented abnormalities in neurological development and behavior, the physiological regulation of metabolism and body composition in males as well as food intake and weight gain in both sexes may be altered by prenatal exposure to toluene.

Exposure to aromatic organic solvents may induce hearing loss in rats, the cochlea being the primary target. The aim of this study which was carried out in rat, was to evaluate the impact of the hepatic metabolism of toluene on its ototoxic potency. To this end, the solvent hepatic metabolism was shifted by treating the rats with 50 mg/kg/d of phenobarbital (PhB), a potent inducer of the microsomal cytochromes P450 system, alcohol and aldehyde dehydrogenases, and glutathione-S-transferases. The two main urinary metabolites of the oxidative and conjugate pathways [hippuric (HA) and benzyl mercapturic acids (BMA) respectively] confirmed the efficacy of the PhB treatment. For the PhB-induced rats, the amount of excreted HA increased by 43% and the amount of BMA by 35%. Auditory function impairments were assessed using auditory-evoked potentials. On completion of the auditory tests, the organs of Corti were dissected to evaluate hair cell losses. The permanent auditory threshold shifts were approximately 15 dB greater in the toluene-exposed rats than in the PhB-induced rats. Both the functional and morphological data confirmed that PhB treatment can decrease the ototoxic potency of toluene.

Ethylbenzene + toluene are known individually to have ototoxic potential at high exposure levels and with prolonged exposure times generally of 4-16 weeks. Both ethylbenzene + toluene are minor constituents of JP-8 jet fuel; this fuel has recently been determined to promote susceptibility to noise-induced hearing loss. Therefore, the current study evaluates the ototoxic potential of combined exposure to ethylbenzene + toluene exposure in a ratio calculated from the average found in three laboratories. Rats received ethylbenzene + toluene by inhalation and half of them were subjected simultaneously to an octave band of noise (OBN) of 93-95 dB. Another group received only the noise exposure which was designed to produce a small, but permanent auditory impairment while an unexposed control group was also included. In two separate experiments, exposures occurred either repeatedly on 5 successive days for 1 week or for 5 days on 2 successive weeks to 4000 mg/m(3) total hydrocarbons for 6 h based upon initial pilot studies. The concentration of toluene was 400 ppm and the concentration of ethylbenzene was 660 ppm. Impairments in auditory function were assessed using distortion product otoacoustic emissions and compound action potential testing. Following completion of these tests, the organs of Corti were dissected to permit evaluation of hair cell loss. The uptake and elimination of the solvents was assessed by harvesting key organs at two time points following ethylbenzene + toluene exposure from additional rats not used for auditory testing. Similarly, glutathione (GSH) levels were measured in light of suggestions that oxidative stress might result from solvent-noise exposures. Ethylbenzene + toluene exposure by itself at 4000 mg/m(3) for 6 h did not impair cochlear function or yield a loss of hair cells. However, when combined with a 93-dB OBN exposure combined solvent + noise did yield a loss in auditory function and a clear potentiation of outer hair cell death that exceeded the loss produced by noise alone. No evidence was found for a loss in total GSH in lung, liver, or brain as a consequence of ethylbenzene + toluene exposure.

Acute exposure to toluene and other volatile organic solvents results in neurotoxicity characterized by nervous system depression, cognitive and motor impairment, and alterations in visual function. In vitro, toluene disrupts the function of N-methyl-D-aspartate (NMDA)-glutamate receptors, indicating that effects on NMDA receptor function may contribute to toluene neurotoxicity. NMDA-glutamate receptors are widely present in the visual system and contribute to pattern-elicited visual-evoked potentials (VEPs) in rodents, a measure that is altered by toluene exposure. The present study tested the hypothesis that effects on NMDA receptors contribute to toluene-induced alterations in pattern-elicited VEPs. Prior to examining the effects of NMDA receptor agonists and antagonists on toluene-exposed animals, a dose-range study was conducted to determine the optimal dose for NMDA (agonist) and MK801 (antagonist). Dose levels of 2.5 mg/kg NMDA and 0.1 mg/kg MK801 were selected from these initial studies. In the second study, Long-Evans rats were exposed to toluene by inhalation, and VEPs were measured during toluene exposure in the presence or absence of NMDA or MK801. Pattern-elicited VEPs were collected by exposing rats to a sinusoidal pattern modulated at a temporal frequency of 4.55 Hz. Following collection of baseline VEPs, rats were injected with either saline, NMDA (2.5 mg/kg, ip), or MK801 (0.1 mg/kg, ip) and 10 min later were exposed to air or toluene (2000 ppm). VEP amplitudes were calculated for 1x (F1) and 2x stimulus frequency (F2). The F2 amplitude was reduced by approximately 60, 60, and 50% in the toluene-exposed groups (TOL): SALINE/TOL (n = 11), NMDA/TOL (2.5 mg/kg; n = 13), and NMDA/TOL (10 mg/kg, n = 11), respectively. Thus, NMDA (2.5 and 10 mg/kg) did not significantly affect toluene-mediated F2 amplitude effects. Administration of 0.1 mg/kg MK801 prior to toluene exposure blocked the F2 amplitude decreases caused by toluene (n = 9). However, when 0.1 mg/kg MK801 was administered 20 min after the onset of toluene exposure, toluene-mediated F2 amplitude decreases persisted despite the challenge by MK801. These data support the hypothesis that acute actions of toluene on pattern-elicited VEPs involve NMDA receptors.

Human and animal studies have shown that toluene can cause hearing loss. In the rat, the outer hair cells are first disrupted by the ototoxicant. Because of their particular sensitivity to toluene, the cochlear microphonic potential (CMP) was used for monitoring the cochlea activity of anesthetized rats exposed to both noise (band noise centered at 4 kHz) and toluene. In the present experiment, the conditions were specifically designed to study the toluene effects on CMP and not those of its metabolites. To this end, 100-microL injections of a vehicle containing different concentrations of solvent were made into the carotid artery connected to the tested cochlea. Interestingly, an injection of 116.2-mM toluene dramatically increased in the CMP amplitude (approximately 4 dB) in response to an 85-dB SPL noise. Moreover, the rise in CMP magnitude was intensity dependent at this concentration suggesting that toluene could inhibit the auditory efferent system involved in the inner-ear or/and middle-ear acoustic reflexes. Because acetylcholine is the neurotransmitter mediated by the auditory efferent bundles, injections of antagonists of cholinergic receptors (AchRs) such as atropine, 4-diphenylacetoxy-N-methylpiperidine-methiodide (mAchR antagonist) and dihydro-beta-erythroidine (nAchR antagonist) were also tested in this investigation. They all provoked rises in CMP having amplitudes as large as those obtained with toluene. The results showed for the first time in an in vivo study that toluene mimics the effects of AchR antagonists. It is likely that toluene might modify the response of protective acoustic reflexes.

Toluene is a commonly abused inhalant. Its neurobiological effects are, at least in part, mediated by gamma-aminobutyric acid (GABA(A)) receptors. Since GABA(A) receptor function is critical during brain development, the long-term effects of toluene exposure during brain growth spurt were investigated. Spargue-Dawley male rats were administered with toluene (500 mg/kg, i.p.) on postnatal day (PN) 4-9. Behavioral and electrophysiological measures and the levels of messenger RNA (mRNA) expression of GABA(A) receptor subunits were examined on PN 28-32. The seizure sensitivity induced by bicuculline (a GABA(A) receptor antagonist), methyl beta-carboline-3-carboxylate (inverse agonists of the GABA(A)/benzodiazepine receptor) but not 3-mercaptopropionic acid (a glutamate decarboxylase inhibitor) was enhanced by toluene exposure. Toluene exposure had no effect on the performance in the elevated plus-maze and rotarod test but reduced the responses to diazepam in these two tests. In vitro intracellular electrophysiological recordings employing brain slices from rats treated with toluene demonstrated a significant decrease in GABA(A) receptor-mediated inhibitory postsynaptic currents in CA1 neurons but an increased response to GABA perfusion. The relative abundance of the mRNAs encoding various subunits of GABA(A) receptor (alpha1, alpha2, alpha4, alpha5, alpha6, beta2, beta3, gamma2S, gamma2L) was examined in four brain regions (hippocampus, striatum, cortex, and cerebellum) by semiquantitative reverse transcription-PCR. These results demonstrated that subunit- and brain area-selective alterations in GABA(A) receptors after toluene exposure during brain growth spurt. The alterations in GABA(A) receptors might be associated with the neurobehavioral disturbance in offspring of toluene-abusing women.

The purpose of this study was to investigate whether the metabolic suppression of hippuric acid (HA) occurs in field workers coexposed to toluene, xylene and ethyl benzene. Eleven male spray painters were recruited into this study and monitored for 2 weeks using a repeated-measures study design. The sampling was conducted for 3 consecutive working days each week. Toluene, ethyl benzene, and xylene in the air were collected using 3M 3500 organic vapor monitors. Urine samples were collected before and after work shift, and urinary HA, methyl hippuric acid, mandelic acid, and phenylgloxylic acid concentrations were determined. In the first week, toluene concentrations were 2.66 +/- 0.95 (mean +/- SE) ppm, whereas ethyl benzene and xylene concentrations were 27.84 +/- 3.61 and 72.63 +/- 13.37 ppm, respectively, for all subjects. Pre-work shift HA concentrations were 230.23 +/- 37.31 mg/g creatinine, whereas pre-work shift HA concentrations were 137.81 +/- 14.15 mg/g creatinine. Mean urinary HA concentration was significantly greater in the pre-work shift samples than in the pre-work shift samples (p = 0.043). In the second week, toluene concentrations were much lower (0.28 ppm), whereas ethyl benzene and xylene were 47.12 +/- 8.98 and 23.88 +/- 4.09 ppm, respectively, for all subjects. Pre-work shift HA concentrations were 351.98 +/- 116.23 mg/g creatinine, whereas pre-work shift HA concentrations were 951.82 +/- 116.23 mg/g creatinine. Mean urinary HA concentration was significantly greater in the pre-work shift samples than in the pre-work shift samples (p

Two expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors, R1 and R2, were operated at 15 degrees C for the treatment of toluene-contaminated volatile fatty acid-based wastewater. The seed inoculum and the R1 reactor were unexposed to toluene, prior to and during the trial, respectively. Both reactors were operated at a hydraulic retention time of 24h at applied organic loading rates of 0.71-1.43kg chemical oxygen demand (COD)m(-3)d(-1). Toluene was supplemented to the R2 influent at concentrations of 5-104 mg toluenel(-1) (solubilised in ethanol). Bioreactor performance was evaluated by COD and toluene removal efficiency, and the methane content of biogas (%). Specific methanogenic activity and toxicity assays were employed to investigate the activity and toluene toxicity thresholds of key trophic groups, respectively, within the seed and reactor biomass samples. COD and toluene removal efficiencies of 70-90% and 55-99%, respectively, were achieved during the 630-d trial. Metabolic assays suggested that a psychrotolerant H(2)/CO(2)-utilizing methanogenic community developed in the toluene-degrading biomass. The results indicate the viability of low-temperature anaerobic digestion for the treatment of wastewater containing toluene.

The influence of toluene concentration on the specific growth rate, cellular yield, specific CO(2), and metabolite production by Pseudomonas putida F1 (PpF1) was investigated. Both cellular yield and specific CO(2) production remained constant at 1.0 +/- 0.1 g biomass dry weight (DW) g(-1) toluene and 1.91 +/- 0.31 g CO(2) g(-1) biomass, respectively, under the tested range of concentrations (2-250 mg toluene l(-1)). The specific growth rate increased up to 70 mg toluene l(-1). Further increases in toluene concentration inhibited PpF1 growth, although inhibitory concentrations were far from the application range of biological treatment processes. The specific ATP content increased with toluene concentration up to toluene concentrations of 170 mg l(-1). 3-Methyl catechol (3-MC) was never detected in the cultivation medium despite being an intermediary in the TOD pathway. This suggested that the transformation from toluene to 3-MC was the limiting step in the biodegradation process. On the other hand, benzyl alcohol (BA) was produced from toluene in a side chain reaction. This is, to the best of our knowledge, the first reported case of methyl monoxygenation of toluene by PpF1 not harboring the pWW0 TOL plasmid. In addition, the influence of 3-MC, BA, and o-cresol on toluene degradation was investigated respirometrically, showing that toluene-associated respiration was not significantly inhibited in the presence of 10-100 mg l(-1) of the above-mentioned compounds.

The effects of 375 mgm(-3) (100 ppm) toluene in air inhalation were evaluated on pigmented rats during either repeated exposures over five consecutive days 3h a day or during a single 4-h exposure. At the end of the inhalation period, the animals were returned to fresh air to evaluate their ability to recover optokinetic performance. The optokinetic responses were analyzed using a magnetic search coil technique previously described. After repeated toluene exposure, the eye position at rest of all the rats was unsteady. In response to visual stimulation, the eye velocity was slower and more irregular than in the control state. At the end of the stimulation, the environment of the animals became stationary, but the eye did not immediately return to a fixed stable position. A similar effect was observed after a single exposure. An increase of the optokinetic deficit was observed after single or repeated 375 mgm(-3) toluene exposures. No recovery was observed even after a single exposure. In view of the fact that toluene is a widely used solvent, these results show that inhalation of low concentrations, even for short single exposures, must be taken into account, because gaze destabilization could cause vertigo symptoms.

Exposure to vapours of volatile chemicals is a major occupational and environmental health concern. Toxicity testing of volatile organic compounds (VOCs) has always faced significant technological problems due to their high volatility and/or low solubility. The aim of this study was to develop a practical and reproducible in vitro exposure technique for toxicity testing of VOCs. Standard test atmospheres of xylene and toluene were generated in glass chambers using a static method. Human cells including: A549-lung derived cell lines, HepG2-liver derived cell lines and skin fibroblasts, were grown in porous membranes and exposed to various airborne concentrations of selected VOCs directly at the air/liquid interface for 1 h at 37 degrees C. Cytotoxicity of test chemicals was investigated using the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) and NRU (neutral red uptake) assays following 24 h incubation. Airborne IC(50) (50% inhibitory concentration) values were determined using dose response curves for xylene (IC(50)=5350+/- 328 ppm, NRU; IC(50)=5750+/- 433 ppm, MTS in skin fibroblast) and toluene (IC(50)=0 500+/- 527 ppm, NRU; IC(50)=11,200 +/- 1,044 ppm, MTS in skin fibroblast). Our findings suggest that static direct exposure at the air/liquid interface is a practical and reproducible technique for toxicity testing of VOCs. Further, this technique can be used for inhalational and dermal toxicity studies of volatile chemicals in vitro as the exposure pattern in vivo is closely simulated by this method.

WOS: 000220395700004, PubMed ID: 15119846, As toluene is an organic solvent, its cytotoxic effect on the cell is known. Similarly, it has been demonstrated that many of the chemical agents that enter the body through smoking have cytotoxic and genotoxic effects on the cells. In this study, the effects of these two toxic agents,both separately and in combination, on leukocyte counts, lymphocyte counts and mitotic index values are investigated. The study was carried out on blood samples of 100 males, divided into four groups: 25 non-smokers and 25 smokers, 25 toluene-exposed non-smokers and 26 no toluene-exposed smokers. The blood cell values of the blood samples were determine automatically on the hemogram apparatus. In addition slides of the blood samples were prepared according to the chromosome analysis procedure and the mitotic index values were determined through microscopy. The possible effects of smoking and toluene on lymphocyte life span was considered by correlating mitotic index values with lymphocyte counts in the same way for each of the subgroups. Results revealed that leukocyte counts and mitotic index values were higher in the smokers than the non-smokers whether or not they had been exposed to toluene. In addition the results indicate that lymphocyte life span may be shortened due to cigarette smoking and toluene exposure.

Rats were exposed to toluene (1,500 ppm for 4 hr per day) for 7 days. The body weight of the rats was significantly lower and the weight of the adrenal gland was significantly higher in the toluene inhalation group compared to the controls. Microscopically, there was no obvious change in the medulla, but hypertrophy of the cortex was observed in the toluene inhalation group. And, the size of adrenocortical cells in treated-rats was also significantly enlarged than the control. Immunohistochemical staining did not show a clear difference in localization of aldosterone-positive cells between the control and inhalation groups. Expansion of the corticosterone-positive area consistent with the cortical hypertrophy was recognized in the inhalation group. Enhancement of 72 kD-heat-shock protein (HSP70)-expression in the toluene inhalation group was not observed. Neither stress nor damage to cortical cells due directly to toluene exposure was observed in the cortex. Also, there was no obvious difference in the anti-proliferating cell nucleus antigen (PCNA)-immunostaining between control and inhalation groups. Thus, it is suspected that cortical hypertrophy was the result of cell enlargement due to the stimulation of the cortical cells. Corticotropin-releasing factor (CRF) immunoreactivity in the paraventricular nucleus (PVN) was increased in the inhalation group. Concentration of plasma ACTH was elevated significantly by toluene exposure. The amounts of mRNA of adrenocortical steroid metabolism gene, cytochrome side-chain cleavage (P450scc), was also increased by toluene inhalation. Toluene exposure might induce adrenocortical hypertrophy via the hypothalamus-pituitary-adrenal gland (HPA) axis.