Effects of six months' white spirit inhalation exposure in adult and old rats

Assessment of the potential human health risks from exposure to complex substances in accordance with REACH requirements. "White spirit" as a case study

The European chemical control regulation (REACH) requires that data on physical/chemical, toxicological and environmental hazards be compiled. Additionally, REACH requires formal assessments to ensure that substances can be safely used for their intended purposes. For health hazard assessments, reference values (Derived No Effect levels, DNELs) are calculated from toxicology data and compared to estimated exposure levels. If the ratio of the predicted exposure level to the DNEL, i.e. the Risk Characterization Ratio (RCR), is less than 1, the risk is considered controlled; otherwise, additional Risk Management Measures (RMM) must be applied. These requirements pose particular challenges for complex substances. Herein, "white spirit", a complex hydrocarbon solvent, is used as an example to illustrate how these procedures were applied. Hydrocarbon solvents were divided into categories of similar substances. Representative substances were identified for DNEL determinations. Adjustment factors were applied to the no effect levels to calculate the DNELs. Exposure assessments utilized a standardized set of generic exposure scenarios (GES) which incorporated exposure predictions for solvent handling activities. Computer-based tools were developed to automate RCR calculations and identify appropriate RMMs, allowing consistent communications to users via safety data sheets.

The sub-chronic toxicity of regular White Spirit in rats

Hydrocarbon solvents are mostly complex substances (UVCB) with carbon numbers in the range of approximately C5-C20. One of the most common types is a C9-C14 aliphatic solvent containing approximately 20% aromatics and commonly known as White Spirit in Europe and mineral spirits in the US. In previous repeated inhalation toxicity studies, White Spirit was reported to cause minimal systemic effects in most animal species with few effects other than male rat-specific kidney changes at levels up to approximately 2000mg/m(3). In the present study male and female rats were exposed to White Spirit vapors, 6h/day, 5days/week for 13weeks at levels of approximately 2000, 4000, or 8000mg/m(3) to assess the potential for effects at higher exposure levels. All of the rats survived the treatment period. In life observations were largely restricted to acute central nervous system (CNS) effects in the high exposure group. Terminal body weights of high exposure groups animals were significantly below control values. Statistically significant differences in the clinical and hematological observations were small and within normal physiological limits. Weights of some organs including liver, spleen and kidneys were elevated, but microscopic examination indicated that the only pathological effects were changes in the kidneys of the male rats, consistent with an α2u-globulin-mediated process, which is gender and species-specific and not relevant to humans. The overall no observed adverse effect level (NOAEC) was 4000mg/m(3).

Chemical Burns and Multiorgan Failure following Acute Ingestion of White Spirit: A Case Report and Review of the Literature

Organic solvents are chemically different compounds with one common feature: they dissolve fats, oils and resins, which makes them widely used in industry. Organic solvents are used in paint and lacquer industries, in the production of pesticides, plastics, explosives and in the pharmaceutical industry. The most common household solvent is white spirit, used as a paint remover. We report a case of acute white spirit ingestion causing multiorgan failure and a prolonged intensive care unit admission. Such a case has not been documented previously and highlights a number of diagnostic and therapeutic considerations. The patient also represents the first reported case of chemical burns from erosive diarrhoea secondary to white spirit ingestion.

Development of α2u-Globulin Nephropathy and Adrenal Medullary Pheochromocytomas in Male Rats Following Exposure to Stoddard Solvent IIC

Stoddard solvent IIC is widely used as a solvent in paints and varnishes, and for dry cleaning and other grease removal applications. Because concern exists regarding the long-term effects of occupational exposure in industrial settings, the toxicity and carcinogenicity of Stoddard solvent IIC were evaluated in male and female F344/N rats and B6C3F1 mice. Rats and mice were exposed to 0, 138, 275, 550, 1100, or 2200 mg/m3 Stoddard solvent IIC by whole-body inhalation for 3 mo, and to 0, 138 (male rats), 550, 1100, or 2200 (female rats and male and female mice) mg/m3 for 2 yr. The kidney, liver, and adrenal medulla were targets of Stoddard solvent IIC toxicity in rats. After 3 mo of exposure, male rats developed lesions characteristic of alpha2u-globulin nephropathy. Male and female rats displayed increased liver weights and/or clinical pathology changes suggestive of hepatic injury, although no accompanying histopathologic changes were observed. After 2 yr, increased incidences of adrenal medullary pheochromocytomas provided some evidence of carcinogenicity in male rats. Renal tubule adenomas were slightly increased in male rats after 2 yr, and may have been related to exposure. In mice, there was no chemical-related toxicity after 3 mo, with the exception of increased liver weights in male mice exposed to 2200 mg/m3. After 2 yr, the incidences of hepatocellular adenomas were increased in female mice exposed to 2200 mg/m3; however, these increases were marginal and associated with increases in body weight. There was no evidence of Stoddard solvent IIC carcinogenicity in female rats or male mice. In summary, inhalation exposures of Stoddard solvent IIC resulted in renal toxicity and adrenal medullary pheochromocytomas in male rats. The liver also appeared to be a site of toxicity in male and female rats and mice.

Review of the Toxicology of Mineral Spirits

This review of the toxicology of mineral spirits covers studies of the major classes of mineral spirits and several toxicologically important mineral spirit constituents. This review cites data from numerous previously unpublished animal toxicology studies conducted on mineral spirits during the past 30 years, expanding the existing database on the toxicology of this group of hydrocarbon solvents. The data can be used to better evaluate the potential effects associated with exposure to these materials, including health and environmental reviews such as the U.S. Environmental Protection Agency High Production Volume (HPV) chemical program and the Organization for Economic Cooperation and Development (OECD) HPV Screening Information Data Set (SIDS) program. The majority of animal toxicology studies in the available literature were conducted on mineral spirits categorized as ASTM D235 Type I Class A (149°C to 213°C boiling range; 8% to 22% aromatics) and demonstrate that Type I Class A mineral spirits have a low order of acute toxicity and do not produce significant systemic effects. Some additional studies conducted with ASTM D235 Type II Class C mineral spirits (177°C to 213°C boiling range; <2% aromatics) suggest that Type II Class C mineral spirits have similar toxicity to Type I Class A mineral spirits, though there is some evidence that Type II, Class C mineral spirits have a lesser degree of central nervous system (CNS) effects than the higher aromatic containing Type I Class A materials. In addition, toxicity data on selected chemical constituents of mineral spirits (e.g., n-nonane, n-decane, n-undecane) indicate that these chemicals have similar toxicological properties to mineral spirits. Overall, the data showed that mineral spirits have a low order of acute toxicity and do not appear to produce toxicologically relevant systemic effects. Ongoing studies are evaluating the concerns associated with chronic low-level exposure and central nervous system effects.

Model studies for evaluating the neurobehavioral effects of complex hydrocarbon solvents

To evaluate the neurobehavioral effects of hydrocarbon solvents and to establish a working model for extrapolating animal test data to humans, studies were conducted which involved inhalation exposure of rats and humans to white spirit (WS). The specific objectives of these studies were to evaluate the behavioral effects of exposure to WS in rats and humans and to determine relationships between internal levels of exposure and behavioral effects. In both animals and volunteers, methods for assessment of similar functional effects were used to enable interspecies comparisons. A battery of tests including standardized observational measures, spontaneous motor activity assessments and learned visual discrimination performance was utilized in rat studies to evaluate acute central nervous system (CNS) depression. Groups of rats were exposed to WS at target concentrations of 0, 600, 2400 or 4800mg/m(3), 8h/day for 3 consecutive days. Blood and brain concentrations of two WS constituents; 1,2,4-trimethylbenzene (TMB) and n-decane (NDEC), were used as biomarkers of internal exposure. In a volunteer study, 12 healthy male subjects were exposed for 4h to either 57 or 570mg/m(3) WS in two test sessions spaced 7 days apart, and neurobehavioral effects were measured using a computerized neurobehavioral test battery. Blood samples were taken at the end of the exposure period to measure internal concentrations of TMB and NDEC. Results of the behavioral tests in rats indicated WS-induced changes particularly in performance and learned behavior. In humans, some subtle performance deficits were observed, particularly in attention. The behavioral effects were related to concentrations of the WS components in the central nervous system. These studies demonstrated a qualitative similarity in response between rats and humans, adding support to the view that the rodent tests can be used to predict levels of response in humans and to assist in setting occupational exposure levels for hydrocarbon solvents.

Neurotoxic effect of maneb in rats as studied by neurochemical and immunohistochemical parameters

Epidemiological investigations document that workers in agriculture, horticulture and people living near areas with frequent use of pesticides have increased risk of developing symptoms of Parkinson's disease. This study investigated the neurotoxic effect of the fungicide maneb by morphological, immunohistochemical and neurochemical methods applying young Sprague-Dawley male rat as the model. Intraperitoneal dosing (7.5, 15 or 30mg maneb/kg bodyweight/week for 12 weeks) demonstrated dose-related increased manganese concentration in corpus striatum. The striatal concentration of 5-hydroxytryptamine (5-HT) increased in a dose-related manner, as did the 5-HT concentrations in the rest of the brain indicating early sign of neurotoxicity. Striatal acetylcholinesterase activity was not affected. The concentrations of noradrenaline, dopamine, neurotransmitter amino acids and the levels of the proteins α-synuclein and synaptophysin in corpus striatum and the rest of the brain were not changed. No histological parameter was affected when studied in corpus striatum and substantia nigra.

Neurological Effects of White Spirit: Contribution of Animal Studies during a 30-Year Period*

Numerous studies have suggested that long-term occupational exposure to white spirit may cause chronic toxic encephalopathy (WHO 1996). This review summarizes the chronic nervous system effects of white spirit in animal studies during a 30-year period. First, routine histopathology was consistently unable to reveal adverse peripheral or central nervous system effects after inhalation of white spirit. Second, neurobehavioural studies in animals showed no adverse effect after inhalation of white spirit with a high content of aromatics in contrast to what was found with products with a low content. Third, white spirit with a high content of aromatics induced adverse neurochemical changes at inhalation of 400 ppm and possibly already at 100 ppm. In the studied parameters, white spirit with a low content of aromatics showed no clear adverse neurochemical effects at inhalation of 400 ppm, but the neurophysiological tests showed adverse effects at this level. Fourth, neurophysiological methods may be more sensitive than histopathological, neurobehavioural and neurochemical methods. Overall, white spirit with a high and a low content of aromatics showed no overt difference in long-term effects in animals, taking all studied end-points into account. The differences in sensitivity of the test methods should be taken into consideration if new toxicological studies are conducted on this type of solvents.

A search for residual behavioral effects of trichloroethylene (TCE) in rats exposed as young adults

Trichloroethylene (TCE) is an organic solvent with robust acute effects on the nervous system, but poorly documented long-term effects. This study employed a signal detection task (SDT) to assess the persistence of effects of repeated daily inhalation of TCE on sustained attention in rats. Adult male Long-Evans rats inhaled TCE at 0, 1600, or 2400 ppm, 6 h/day for 20 days (n=8/group) and began learning the SDT 3 weeks later. Rats earned food by pressing one retractable response lever in a signal trial and a second lever in a blank (no signal) trial. TCE did not affect acquisition of the response rule or performance of the SDT after the intertrial interval (ITI) was changed from a constant value to a variable one. Increasing the trial presentation rate reduced accuracy equivalently in all groups. Injections of ethanol (0, 0.5, 1.0, 1.5 g/kg ip) and d-amphetamine (0, 0.1, 0.3, 1.0 mg/kg sc) systematically impaired performance as functions of drug dose. d-Amphetamine (1.0 mg/kg) reduced P(hit) more in the 2400-ppm TCE group than in the other groups. All rats required remedial training to learn a reversal of the response contingencies, which TCE did not interfere with. Thus, a history of exposure to TCE did not significantly alter learning or sustained attention in the absence of drugs. Although ethanol did not differentially affect the TCE groups, the effect of d-amphetamine is consistent with solvent-induced changes in dopaminergic functions in the CNS. Calculations indicated power values of 0.5 to 0.8 to detect main effects of TCE for the three primary endpoints.

Effects of white spirits on rat brain 5-HT receptor functions and synaptic remodeling

Previously, inhalation exposure to different types of white spirit (i.e. complex mixtures of aliphatic, aromatic, alkyl aromatic, and naphthenic hydrocarbons) has been shown to induce neurochemical effects in rat brains. Especially, the serotonergic system was involved at the global, regional, and subcellular levels. This study investigates the effects of two types of white spirit on 5-hydroxytryptamine (5-HT) transporters (5-HTT), 5-HT(2A) and 5-HT(4) receptor expression in forebrain, and on neural cell adhesion molecule (NCAM) and 25-kDa synaptosomal associated protein (SNAP-25) concentrations when applied as indices for synaptic remodeling in forebrain, hippocampus, and entorhinal cortex. Male Wistar rats were exposed to 0, 400, or 800 ppm of aromatic (20 vol.% aromatic hydrocarbons) or dearomatized white spirit (catalytically hydrogenated white spirit) in the inhaled air for 6 h/day, 7 days/week for 3 weeks. The 5-HTT B(max) and K(d) were not affected. Both types of white spirit at 800 ppm decreased B(max) for the 5-HT(2A) receptor. The aromatic type decreased the K(d) of the 5-HT(2A) and 5-HT(4) receptors at 800 ppm. Aromatic white spirit did not affect NCAM or SNAP-25 concentrations or NCAM/SNAP-25 ratio in forebrain, whereas NCAM increased in hippocampus and the NCAM/SNAP-25 ratio decreased in entorhinal cortex. Dearomatized white spirit did not affect NCAM, SNAP-25, or NCAM/SNAP-25 ratio in any brain region. The affected 5-HT receptor expression and synaptic plasticity marker proteins indicate that inhalation exposure to high concentrations of white spirit may be neurotoxic to rats, especially the aromatic white spirit type.

The effect of aliphatic, naphthenic, and aromatic hydrocarbons on production of reactive oxygen species and reactive nitrogen species in rat brain synaptosome fraction: the involvement of calcium, nitric oxide synthase, mitochondria, and phospholipase A11Abbreviations: BIM, bisindolylmaleimide; [Ca2+]i, concentration of intracellular calcium; ChAT, cholin acetyltransferase; CSA, cyclosporin A; DCF, 2′,7′-dichlorofluorescein; H2DCF-DA, 2′,7′-dichlorodihydrofluorescin diacetate; DEDA, dimethyleicosadienoic acid; ERK, extracellular signal-regulated kinases; Fura-2 AM, 5-oxazolecarboxylic acid, 2-(6-(bis(2-((acetyloxy)methoxy)-2-oxoethyl)amino)-5-(2-(bis(2-((acetyloxy)methoxy)-2oxoethyl)amino)-5-methylphenoxy)ethoxy)-2-benzofuranyl)-, (acetyloxy) methyl ester; GABA-T, gamma-aminobutyric acid transaminase; HBSS, Hanks’ balanced salt solution; La3+, lanthanum; MAPK, mitogen-activated protein kinase; MeHg, methyl mercury; MEK, extracellular signal-regulated protein kinase; MeOH, methanol; MTP, mitochondrial permeability transition pore; L-NAME, Nω-nitro-l-arginine methyl ester; NO·, nitrogen oxide; NOS, NO· synthase; O2·−, superoxide; PLA2, phospholipase A2; PKC, protein kinase C; RNS, reactive nitrogen species; ROS, reactive oxygen species; SOD, superoxide dismutase; TMB, 1,2,4-trimethylbenzene; TMCH, 1,2,4-trimethylcyclohexane; and U73122, 1-(6-[17beta-3-methoxyestra- 1,3,5(10)-trien- 17-yl]-aminohexyl)- 1H-pyrrole-2,5-dione

This study investigated the effects of C7 and C9 aliphatic (n-heptane, n-nonane), naphthenic (methylcyclohexane, 1,2,4-trimethylcyclohexane (TMCH)) and aromatic (toluene, 1,2,4-trimethylbenzene (TMB)) hydrocarbons on the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in rat brain synaptosome fraction. Methyl mercury (MeHg) was included as a positive control. Exposure of the synaptosomes to the hydrocarbons produced a concentration-dependent linear increase in the formation of the fluorescence of 2',7'-dichlorofluorescein (DCF) as a measure of the production of ROS and RNS. Formation of RNS was demonstrated by preincubation of the synaptosome fraction with the neuronal nitric oxide synthase (nNOS) inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME), which reduced the MeHg and TMCH-stimulated fluorescence by 51% and 65%, respectively. The naphthenic hydrocarbon TMCH showed the strongest potential for ROS and RNS formation in rat brain synaptosomes, followed by TMB, toluene, n-nonane, n-heptane, and methylcyclohexane, respectively. TMCH was selected for mechanistic studies of the formation of ROS. Both MeHg and TMCH induced an increase in intracellular calcium concentration [Ca(2+)]i as measured with Fura-2. Blockade of voltage-dependent Ca(2+) channels with lanthanum prior to stimulation with MeHg and TMCH led to a reduction in the ROS/RNS formation of 72% and 70%, respectively. Furthermore, addition of cyclosporin A (CSA), a blocker of the mitochondrial permeability transition pore (MTP), lowered both the MeHg and TMCH-elevated DCF fluorescence by 72% and 59%. Preincubation of the synaptosome fraction with the protein tyrosine kinase inhibitor genistein lowered the MeHg and TMCH-stimulated fluorescence by 85% and 91%, respectively. Addition of the extracellular signal-regulated protein kinase (MEK)-1 and -2 inhibitor U0126 reduced the fluorescence stimulated by MeHg and TMCH by 62% and 63%. Furthermore, the protein kinase C inhibitor bisindolylmaleimide reduced the fluorescence stimulated by MeHg and TMCH by 52% and 56%. The compound 1-(6-[17beta-3-methoxyestra- 1,3,5(10)-trien- 17-yl]-aminohexyl)-1H-pyrrole-2,5-dione (U73122), which inhibits phospholipase C, was shown to decrease the ROS and RNS formation induced by MeHg and TMCH by 49% and 64%, respectively. The phospholipase A2 (PLA2) inhibitor 7,7-dimethyl eicosadienoic acid (DEDA) reduced fluorescence in response to MeHg and TMCH by 49% and 54%. Simultaneous addition of L-NAME, CSA, and DEDA to the synaptosome fraction totally abolished the DCF fluorescence. In conclusion, C7 and C9 aliphatic, naphthenic, and aromatic hydrocarbons stimulated formation of ROS and RNS in rat brain synaptosomes. The naphthenic hydrocarbon TMCH stimulated formation of ROS and RNS in the synaptosomes through Ca(2+)-dependent activation of PLA2 and nNOS, and through increased transition permeability of the MTP. Exposure of humans to the naphthenic hydrocarbon TMCH may stimulate formation of free radicals in the brain, which may be a key factor leading to neurotoxicity.

Inhalation exposure to white spirit causes region-dependent alterations in the levels of glial fibrillary acidic protein

Enhanced expression of glial fibrillary acidic protein (GFAP) is known to be associated with toxicant-induced gliosis, a homotypic response of the central nervous system to neural injury. A variety of neurochemical and neurophysiological effects have been observed in experimental animals exposed to white spirit, but a linkage of such effects to neural damage has not been established. Here we evaluated the regional levels of GFAP to assess potential sites of CNS damage in the rat, following exposure to dearomatized and aromatic white spirit. Samples from rats exposed to dearomatized white spirit were assayed for GFAP levels in the United States and Denmark. The results were remarkably similar between countries. Small region-dependent increases and decreases in GFAP were observed with the cerebellum showing the most consistent effects (increases). In contrast, samples from rats exposed to aromatic white spirit showed large (as much as 150% of control) increases in regional levels of GFAP; again, the cerebellum showed the most consistent effects. The data are indicative of an aromatic white-spirit-induced astrogliosis in several regions of the rat CNS and suggest that chronic exposure to this solvent may be associated with underlying neural damage.

Distribution of dearomatised white spirit in brain, blood, and fat tissue after repeated exposure of rats

Petroleum products with low content of aromatics have been increasingly used during the past years. This study investigates tissue disposition of dearomatised white spirit. In addition, brain neurotransmitter concentrations were measured. Male rats were exposed by inhalation to 0, 400 (2.29 mg/1), or 800 p.p.m. (4.58 mg/l) of dearomatised white spirit, 6 hr/day, 5 days/week up to 3 weeks. Five rats from each group were sacrificed immediately after the exposure for 1, 2, or 3 weeks and 2, 4, 6, or 24 hr after the end of 3 weeks' exposure. After 3 weeks of exposure the concentration of total white spirit was 1.5 and 5.6 mg/kg in blood; 7.1 and 17.1 mg/kg in brain; 432 and 1452 mg/kg in fat tissue at the exposure levels of 400 and 800 p.p.m., respectively. The concentrations of n-nonane, n-decane, n-undecane, and total white spirit in blood and brain were not affected by the duration of exposure. Two hours after the end of exposure the n-decane concentration decreased to about 25% in blood and 50% in brain. A similar pattern of elimination was also observed for n-nonane, n-undecane and total white spirit in blood and brain. In fat tissue the concentrations of n-nonane, n-decane, n-undecane, and total white spirit increased during the 3 weeks of exposure. The time to reach steady-state concentrations is longer than 3 weeks. After the 3 weeks' exposure the fat tissue concentration of n-nonane, n-decane, n-undecane, and total white spirit decreased very slowly compared with the rate of decrease in blood and brain suggesting that long-lasting redistribution from fat to brain may occur. One week of exposure at 800 p.p.m. caused a statistically significant increase in whole brain dopamine concentration while the noradrenaline concentration was unaffected. Exposure at both exposure levels for 1 week caused a statistically significantly decreased concentration of 5-hydroxytryptamine in whole brain. The reduction was related to the exposure concentration. These changes in neurotransmitter concentrations were normalised after 2 and 3 weeks' exposure. In conclusion, after 3 weeks of exposure the fat:brain:blood concentration coefficients for total white spirit were approximately 250:3:1, and redistribution from fat to brain is possible. As total white spirit behaved similarly to the n-alkanes in blood, brain, and fat tissue, we suggest that the non-n-alkane white spirit components possess toxicokinetic properties similar to the n-alkanes.

Four weeks' inhalation exposure of rats to p-cymene affects regional and synaptosomal neurochemistry

Long-lasting effects of inhalation exposure to p-cymene (p-isopropyl-toluene; CAS No. 99-87-6) on regional and subcellular brain neurochemistry were studied. Male Long-Evans rats were exposed to 0, 50, or 250 p.p.m. p-cymene 6 hr/day, 5 days/week for four weeks followed by an exposure-free period of 8 weeks. Synaptosomes were isolated from whole brain minus cerebellum and used as an ex situ model for in situ conditions at the level of the presynaptic nerve terminal. There was no persistent effect on wet weight (regional) or regional noradrenaline (NA), dopamine (DA), or 5-hydroxytryptamine (5-HT) concentrations owing to exposure. Yield of synaptosomal protein was statistically significantly reduced in an exposure concentration-related manner (Control: 16.6 +/- 3.1; 50 p.p.m.: 9.2 +/- 2.1; 250 p.p.m.: 8.6 +/- 1.7 mg protein/g tissue, mean +/- I.S.D.). Synaptosomal NA and DA concentrations and acethycholinesterase, butyrylcholinesterase, and lactate dehydrogenase activities were statistically significantly increased when expressed relative to synaptosomal protein. It is hypothesized that a reduced density and number of synapses in situ are functionally compensated for by increased NA and DA release from noradrenergic and dopaminergic presynaptic nerve terminals. The applicability of the synaptosome as an ex situ neurochemical research model for the presynaptic CNS nerve terminal in situ for the study of solvent neurotoxicity in rats was further supported.

Dearomatized white spirit inhalation exposure causes long-lasting neurophysiological changes in rats

Exposure for 6 h per day, 5 days per week, during a period of 6 months to the organic solvent dearomatized white spirit (0, 400, and 800 ppm) was studied in rats that were 3 months old when the repeated exposure was initiated. After an exposure-free period of 2-6 months duration, neurophysiological, neurobehavioral, and macroscopic pathologic examinations were performed. The study revealed exposure-related changes in sensory evoked potentials and a decrease in motor activity during dark (no light) periods but no white spirit-induced changes in learning and memory functions. The measurements of the flash evoked potential (FEP), somatosensory evoked potential (SEP), and auditory brain stem response (ABR) all demonstrated dose-dependent increases of the amplitudes of the early latency peaks of the sensory evoked potentials (EPs). Furthermore, an increase of the dose showed that the measurements of FEP and SEP revealed changes in the later-latency peaks, which reflect the more associative aspects of sensory processing. The results demonstrated that 6 months of exposure to dearomatized white spirit induced long-lasting and possible irreversible effects in the nervous system of the rat.

Changes in markers of oxidative status in brain, liver and kidney of young and aged rats following exposure to aromatic white spirit

Levels of glutathione and activity of glutamine synthetase were assayed in organs of rats following inhalation of a heterogeneous solvent mixture containing both aliphatic and aromatic hydrocarbons. This mixture was administered for 3 weeks (6 h daily) at two levels in the inhaled air (400 and 800 ppm) to young adult (5-month-old) and aged (14-month-old) rats. Depression of levels of glutamine synthetase in the P2 fraction of kidney was observed, which was more severe in aged than young adult rats. Glutamine synthetase is a cytosolic enzyme especially susceptible to oxidative damage. A parallel depression of this enzyme was also seen in the corresponding hepatic fractions. However, levels of glutamine synthetase in the hippocampus were elevated by this exposure. Glutathione levels were depressed in P2 fractions of livers of exposed rats, and also in the corresponding renal fraction. Glutathione concentration was unchanged in cerebral fractions. Overall results were interpreted to imply that pro-oxidant events were elevated in kidney and liver following prolonged inhalation of the solvent mixture. The changes found in brain tissue did not reveal evidence of oxidative stress but, however, suggested that glial activation was taking place.

Three weeks' exposure of rats to dearomatized white spirit modifies indices of oxidative stress in brain, kidney, and liver

The present study was undertaken in order to investigate whether dearomatized white spirit induces indices of oxidative stress in subcellular fractions of hemisphere, hippocampus, kidney and liver tissue of rats exposed to 0, 400 and 800 ppm 6 hr/day, 7 days a week for 3 weeks. The results show that white spirit is a strong in vivo inducer of oxidative stress in subcellular fractions of brain, kidney and liver. In the liver there was a statistically significant increase in the rate of reactive oxygen species (ROS) generation and a decrease in glutamine synthetase activity. In the kidney there was a statistically significant decrease in the rate of ROS generation. In the hemisphere there was a statistically significant increase in the level of reduced glutathione. In the hippocampus there was a statistically significant increase in the rate of ROS generation. However, in vitro addition of dearomatized white spirit had no effect on the rate of cerebrocortical P2 fraction ROS generation. The results suggest that cumulative oxidative damage may be an underlying mechanism of dearomatized white spirit-induced neurotoxicity and that various regions of the brain may respond differently.