Role of the adrenal medulla in control of blood pressure and renal function during frusemide-induced volume depletion.

OBJECTIVE: To examine the role of the adrenal medulla in reflex control of mean arterial pressure (MAP), heart rate and renal function parameters during frusemide-induced volume depletion. DESIGN: Frusemide (6 mg/kg per h) was administered intravenously to two groups of chronically instrumented rats with either sham adrenal medullectomy (n = 15) or adrenal medullectomy (n = 11). RESULTS: Adrenal medullectomy reduced adrenal adrenaline concentration by 99% and plasma adrenaline concentration by 97%. Plasma corticosterone levels were similar in the two groups, which suggests that adrenal cortical function was not affected by adrenal medullectomy. Although frusemide did not affect arterial pressure in the sham-operated rats, MAP fell by 21 +/- 3 mmHg (mean +/- SEM) during frusemide diuresis in the rats with adrenal medullectomy. Heart rate was lower in the rats with adrenal medullectomy than in the sham-operated rats throughout the study. There were no major differences in renal haemodynamics or overall renal water and sodium handling between the two groups but, at the time of maximal activation of compensatory sodium reabsorption, fractional sodium excretion in the distal nephron segment was significantly higher in the rats with adrenal medullectomy than in the sham-operated rats. CONCLUSIONS: Adrenal medullary adrenaline release is essential in the control of MAP during frusemide-induced volume depletion. Circulating adrenaline might contribute, by modifying distal tubular sodium reabsorption, to compensatory sodium reabsorption during frusemide-induced volume depletion.

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.

Neuronal loss in hippocampus in rats exposed to toluene.

Both clinical and epidemiological studies of the effects of exposure to toluene have shown that long-term exposure may result in chronic toxic encephalopathy, where one of the major symptoms is memory deficits. We have attempted to identify the structural basis of the toxic effects of toluene in the hippocampus, a region of the brain known to be involved in learning and memory processes and well suited for stereological analysis. Rats were exposed to 1500 ppm of toluene, six hours per day, five days per week for six months. This was followed by a four-month-period without exposure prior to sacrifice. The total number of neurons in each of the five subdivisions of hippocampus of six exposed and six control rats was estimated with the optical fractionator. A statistically significant neuron loss of 16% was found in regio inferior (CA3 and CA2) of the exposed rats.

Effect on the content of n-acetylaspartate, total creatine, choline containing compounds, and lactate in the hippocampus of rats exposed to aromatic white spirit for three weeks measured by NMR spectroscopy.

Several epidemiological studies of workers occupationally exposed to white spirit show that neuropsychiatric disorders are a frequent cause of early disability pension in this population compared with non-exposed controls. In the rat, we have demonstrated that exposure to different kinds of white spirit induces changes in neurotransmitter concentrations, indices of oxidative stress, and electrophysiological parameters. Others have confirmed that acute behavioural effects can be induced by short-term high-level exposure. With NMR spectroscopy technique it is possible to study neurochemical parameters in vivo, and to examine the same subjects repeatedly over time. NMR spectroscopy was used to study the effects of organic solvents in rats. Rats were exposed to 0, 400 ppm, or 800 ppm of aromatic white spirit 6 hr/day, 7 days/week for 3 weeks. During the first week, the rats showed signs of irritation of mucous membranes, and appeared to be sedated. Both types of effect gradually diminished during the second week. The rats were examined by single volume of interest (VOI) NMR spectroscopy. N-acetylaspartate, creatinine and phosphocreatinine, and choline containing compounds were measured in the hippocampus and surrounding regions. The concentration of N-acetylaspartate for the three groups was found to be in the range of 8.2-8.5 mM with a standard deviation of 0.6-0.9. There was no difference between the three groups. In a previous study no change in the number of astrocytes in hippocampus was found following exposure to white spirit for six months. Since N-acetylaspartate is thought to be a marker for neurons, the results of these two studies indicate that white spirit does not produce a marked neuronal loss. However, it was not possible to show effect of trimethyltin. In this study trimethyltin was used as a "positive control'. The NMR technique can be applied to the rat, and it is possible to obtain reasonable signal-to-noise ratios.

Toxicity of the styrene metabolite, phenylglyoxylic acid, in rats after three months' oral dosing.

Male Wistar rats were dosed with 0, 1250, 3750 or 5000 mg/l of phenylglyoxylic acid (PGA) (CAS no. 611-73-4) in the drinking water ad libitum for 3 months. During the entire treatment period, there were no gross signs of toxicity related to PGA. No changes in neurobehavior were found after using a functional observational battery or radial arm maze. An increased relative kidney weight was seen in the highest dose-group (Controls: 0.504 +/- 0.031 g/100 g b.wt.; 5000 mg PGA/l: 0.579 +/- 0.033 g/100 g b.wt.; p<0.01). No other organ weights were affected. Histopathology revealed no change in kidney structure. No changes in clinical biochemistry. In the highest dose-group three animals out of ten showed reduction in peripheral nerve myelin sheath thickness. No such changes were seen in the control group. The study revealed no changes in auditory brain stem response but minor changes in electroretinography. The noradrenaline (NA) concentration decreased in pons and thalamus whereas it increased in medulla oblongata and whole brain. The dopamine (DA) concentration increased in cerebellum, hippocampus, pons, and whole brain. The most marked DA increase was seen in hippocampus (Controls: 0.56 +/- 0.10 nmol/g tissue; 5000 mg/l: 1.04 +/- 0.11 nmol/g tissue; p<0.001). The 5-hydroxytryptamine (5-HT) concentration decreased in cerebellum, cerebral cortex, hippocampus, and medulla oblongata, whereas it increased in thalamus. The yield of synaptosomal protein, synaptosomal NA, DA, and 5-HT concentrations, and DA uptake rate were not affected. When dosed males were mated with naive females, there were no differences between groups in the pregnancy rate, number of corpora luteae, implantations, live or dead fetuses, resorptions, preimplantation loss, or postimplantation loss. It is concluded that a part of the effects on kidney, peripheral nerves, and vision, which have previously been reported after exposure to styrene, might be induced by the styrene metabolite, PGA. If PGA has ototoxic effects in rats, the dosing in the present study is not sufficient to induce the necessary ototoxic concentration in blood. Alternatively, the ototoxicity of styrene, like toluene, may be caused the parent compound itself and not by a metabolite like PGA.

Three weeks' and six months' exposure to aromatic white spirit affect synaptosomal neurochemistry in rats.

The effects of 3 weeks' or 6 months' inhalation exposure of rats to aromatic white spirit 6 h/day, 5 days/week at 0, 400, or 800 ppm were studied. Synaptosomal neurochemistry was investigated as index of the in situ conditions in the presynaptic nerve terminal. In both studies, the relative and absolute yield of synaptosomal protein were significantly reduced in the two exposed groups. Both studies demonstrated increased synaptosomal noradrenaline (NA), dopamine (DA), and 5-hydroxytryptamine (5-HT) concentrations, high- affinity 5-HT uptake rate and uptake capacity. It is hypothesized that a reduced density and total number of synapses in situ may be functionally compensated by increased NA, DA, and 5-HT neurotransmitter release, or by increased activity of corresponding neurons. The increased synaptosomal 5-HT uptake rates and uptake capacities may explain the previously demonstrated increased global and regional neurotransmitter concentrations and the present finding of increased synaptosomal 5-HT concentrations. These changes are interpreted as an indication of toxic effect on the CNS function and are considered supportive of recent findings of electrophysiological changes and affected motor activity following 6 months' exposure to dearomatized white spirit followed by an exposure-free period.

The acute effects of mono(2-ethylhexyl)phthalate (MEHP) on testes of prepubertal Wistar rats.

A single oral dose of 400 mg/kg body weight of mono(2-ethylhexyl)phthalate (MEHP), the testis toxic metabolite of di(2-ethylhexyl)phthalate, was given to 28-day-old male Wistar rats and the testis toxic effects were investigated 3,6, and 12 h after exposure. Detachment and sloughing of germ cells were observed, and in the Sertoli cells the cytoplasmatic intermediate filament vimentin collapsed. In the immunohistochemical investigation the androgen receptor distribution was unchanged between the control group and treated groups. The expression of the testosterone-repressed-prostatic-message-2 gene in rat testis increased after 3 h, but returned to control levels after 6 and 12 h. Caspase-3 activity increased 3 and 12 h after MEHP exposure. This increase could not be correlated to an increase in DNA fragmentation or increase in apoptotic numbers of germ cells. In conclusion, the effect of MEHP in testis is apparently not involving the androgen receptor. Vimentin localisation in the Sertoli cells, and increased levels of caspase-3 activity appear to be sensitive and early markers of MEHP testis toxicity.

Mutagens in rat urine after dermal application of 1,3-diaminobenzene.

The mutagenicity of urine from rats treated topically on the skin with 1,3-diaminobenzene was studied by the Salmonella/mammalian-microsome assay. Urine samples were either passed directly through micropore filters or extracts were prepared using XAD-2 resin before testing in the frameshift strain TA98. Significant mutagenic activity was found only after metabolic activation with rat-liver microsomes. The activity was higher in extracts from rats treated with a mixture of hydrogen peroxide and 1,3-diaminobenzene than from rats which were exposed to 1,3-diaminobenzene only. After fractionation of the urine by HPLC it could be demonstrated that the mutagenic activity was not due to the parent amine but related to metabolites in two of the fractions. To a lesser extent these two partially purified fractions were also mutagenic without S9 activation even though it was not possible to demonstrate this effect in unfractionated urine extracts. A third fraction containing two metabolites did not exert demonstrable mutagenic activity. The implications for the assessment of hazard to man are discussed.

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.

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.

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.

Effects of 2,5-hexanedione alone and in combination with acetone on radial arm maze behavior, the "brain-swelling" reaction and synaptosomal functions.

A multidisciplinary study to investigate 2,5-hexanedione (2,5-HD)-induced CNS-neurotoxicity and its proposed potentiation by acetone (AC) was conducted. Neurobehavioral testing, estimation of the brain-swelling reaction, neuropathological and morphometric measurements as well as synaptosomal 5-hydroxytryptamine (5-HT) uptake were evaluated. Male Wistar rats were exposed through their drinking water, for seven weeks, either to 0.5% 2,5-HD alone or to 0.5% 2,5-HD in combination with 0.5% AC. This 2,5-HD dose is known to cause neurotoxicity in the peripheral nervous system. Exposed animals were compared to a control group that received tap water. Acquisition but not performance of spatial learning, as measured in the radial 8-arm maze, was significantly inhibited by the coexposure to 2,5-HD and AC. Brain weights of rats exposed to 2,5-HD alone and to 2,5-HD and AC in combination, were slightly, albeit significantly, reduced. Synaptosomal high-affinity 5-HT uptake rate and uptake capacity were significantly reduced by 2,5-HD alone and in combination with AC. The morphometric results are reported in a companion paper. In conclusion, the present findings indicate that 2,5-HD is a CNS-neurotoxicant. The hypothesis about AC potentiation of 2,5-HD CNS-neurotoxicity was supported.

Total number and mean cell volume of neocortical neurons in rats exposed to 2,5-hexanedione with and without acetone.

The toxicological effects of 2,5-hexanedione (2,5-HD) alone and combined with acetone on the number and size of neurons in the cerebral cortex of rats were evaluated with stereological techniques. Thirty rats were equally divided into three groups: One control, one receiving 0.5% 2,5-HD, and one receiving 0.5% 2,5-HD and 0.5% acetone in the drinking water for seven weeks. Unbiased estimates of the total number of neocortical neurons, as well as the mean neuronal nuclei and cell body volumes were obtained from systematically sampled 3.5-microns sections. The total number of neurons in the 2,5-HD group was significantly smaller than the control group (p less than 0.05, one-tailed t-test). Both test groups showed significant changes in the mean cell body volume: Compared with the control group, animals exposed to 2,5-HD had 11% smaller cell body volumes while animals exposed to 2,5-HD and acetone had 13% larger cell body volumes. These data represent the first unbiased estimation of mean cell volume in toxicology. We propose the nucleator method as an efficient and accurate tool for estimating quantitative changes in toxicological research.

In vitro and in vivo studies on the metabolism of 1,3-diaminobenzene: Comparison of metabolites formed by the perfused rat liver, primary rat hepatocyte cultures, hepatic rat microsomes and the whole rat.

The metabolism of the aromatic amine 1,3-diaminobenzene (MPD) was studied in vitro by use of the perfused rat liver, primary rat hepatocyte cultures and hepatic rat microsomes. The metabolites formed were compared with urinary metabolites excreted by the rat in vivo. Metabolites of [(14)C]MPD excreted by the perfused liver were found to be identical with urinary excreted metabolites in vivo, three of which were found to correlate with the N-acetylated derivatives N,N'-diacetyl-1,3-diaminobenzene, N,N'-diacetyl-2,4-diaminophenol and N-acetyl-1,3-diaminobenzene. Also, the primary hepatocyte cultures formed the metabolites found in the urine. However, several other metabolites, including some glucuronic acid conjugates, could be detected in the culture medium. In contrast to the perfused liver and the primary hepatocyte cultures, a reconstituted microsomal system was unable to form any of the metabolites formed by the other in vitro models and in vivo. The results show that in addition to the metabolites that can be detected in the urine in vivo, several other derivatives, including glucuronic acid conjugates of MPD, are formed by the rat liver. The results suggest that primary rat hepatocyte cultures are the preferred model system in metabolic studies in vitro and will constitute useful supplements to metabolic studies performed in the rat in vivo.

Percutaneous absorption, biotransformation, retention and excretion of 1,3-diaminobenzene in the rat.

Groups of seven male Wistar rats were dermally exposed for 24 hr to 556 mumol [14C]meta-phenylenediamine (MPD; 1,3-diaminobenzene) in either aqueous solution (Group 2) or 4% hydrogen peroxide (Group 3). The percutaneous absorption and the amount of non-excreted radioactivity were significantly higher in Group 2 rats. Radioactivity associated with DNA purified from the liver and kidneys was demonstrated. Urine was the principal route of excretion, especially in Group 2 rats. Rats in Group 3 excreted significantly more MPD in the faeces than did Group 2 rats. Urinary excretion of material that constituted two of the peaks in the high-performance liquid chromatogram demonstrated first-order elimination kinetics. Three N-acetylated metabolites (N-acetyl-1,3-diaminobenzene, N,N'-diacetyl-2,4-diaminophenol and N,N'-diacetyl-1,3-diaminobenzene) accounted for 49 and 37% of the urinary excretion of group 2 and 3 rats, respectively, indicating that such metabolites represent important pathways in the metabolism of MPD. Minor excretion of at least one highly hydrophilic, unidentified metabolite of MPD was demonstrated. High-performance liquid chromatographic analysis of urine indicated that the XAD-2 purification procedure, which is usually used before mutagenicity testing in vitro, resulted in some of the radioactive materials being discarded. The percutaneous absorption of MPD in vivo was compared with the permeability of isolated epidermal membranes in vitro. These studies showed that such in vitro studies might be used to predict the dermal absorption by rats, in vivo, of MPD and similar, topically applied compounds.

Repeated dose 28-day oral toxicity study in Wistar rats with a mixture of five pesticides often found as residues in food: alphacypermethrin, bromopropylate, carbendazim, chlorpyrifos and mancozeb.

Six dose groups of 8 male and female rats respectively received a daily dose equivalent to 0, 0.15, 0.006, 0.03, 0.15 or 0.3 mg/kg b.w./day chlorpyrifos (groups 1-6) and the last four dose groups (groups 3-6) received in addition daily doses equivalent to 18 mg/kg b.w./day alphacypermethrin, 30 mg/kg b.w./day bromopropylate, 45 mg/kg b.w./day carbendazim and 12.5 mg/kg b.w./day mancozeb for 28 days. Plasma acetylcholinesterase was significantly decreased in the groups 2, 5 and 6 males. Total white blood cell count was significantly lower in females of group 6. Total red blood cell count, haematocrite and haemoglobin concentration was significantly reduced in both male and female rats of groups 5 and 6. Relative liver weight was significantly increased in groups 3-6 male and female rats. Absolute thyroid gland weight was significantly increased in groups 3, 5 and 6 male rats and of groups 3-6 female rats, and relative thyroid gland weight was significantly increased in groups 2-6 male rats and of groups 3-6 female rats. Absolute thymus weight of groups 3-6 male and female rats and relative thymus weight of groups 3-6 male rats and groups 3 and 4 female rats was significantly decreased. A mild degree of centrilobular cell hypertrophy of the liver was seen in all male rats and of three female rats of group 6. In the thyroid gland follicular cell hypertrophy was present in one female in the control group and in six females and seven males of group 6. It was concluded that inhibition of acetylcholinesterase activity in plasma and brain by chlorpyrifos was not enhanced by co-administration of the other four pesticides. Effects were seen in liver, thyroid, thymus and blood in the combination groups. However, identification of the pesticide(s) responsible for these changes would require further studies of the individually pesticides as well as various combinations of the pesticides.

Regional and subcellular localization of Li+ and other cations in the rat brain following long-term lithium administration.

Rats were given LiCl in their diet (40 mmol/kg dry weight) for at least 3 months to elucidate the regional and subcellular localization of Li+ in the brain as well as the effect of chronic lithium administration on the distribution of other cations. At steady-state the mean concentrations of Li+ were 0.66 mmol/kg wet weight in the whole brain and 0.52 mM in plasma. The tissue/plasma concentration ratio exceeded unity in all anatomical regions. No region showed excessive accumulation of Li+. Whole brain or regional contents of Na+ or K+ were unaffected by lithium treatment. Subcellular Li+ localization was demonstrated in nuclear, crude mitochondrial, and microsomal fractions of whole brain homogenate. Subfractionation of the crude mitochondrial fraction revealed energy-independent intrasynaptosomal and intramitochondrial Li+ and K+ localization at 0-4 degrees C. Li+ administered in vivo disappeared within 10 min from synaptosomes incubated at 37 degrees C. Li+ added in vitro at 1 mM attained a synaptosomal steady-state concentration within 30 min at 37 degrees C. In control rats, synaptosomal concentrations and synaptosomal/medium concentration gradients of cations paralleled their respective in vivo concentrations and gradients. Lithium treatment caused synaptosomal depletion of K+ and Mg2+ and hence probably partial membrane depolarization. Addition of 1 mM Li+ in vitro also caused synaptosomal Mg2+ depletion. The results indicate that Li+ is "accumulated" in brain sediments and synaptosomes following its long-term treatment. The estimated intracellular and intrasynaptosomal Li+ concentrations are lower than predicted by passive distribution according to the Nernst equation, evidencing active extrusion of Li+.

Human platelet 5-hydroxytryptamine concentration as a tool in prediction of solvent induced neurotoxic effects.

Many organic solvents are lipophilic and concentrate in lipid rich tissues e.g. nervous tissue, where they are known to induce toxic effects in humans, especially in the central nervous system. Changes in the presynaptic neurotransmitter metabolism may play a role in these effects. The platelet is proposed as an alternative human model for this complex in the investigation of such changes, especially regarding 5-hydroxytryptamine (5-HT). The platelet 5-HT concentration was measured in platelets isolated from exposed persons with diagnosed neurointoxication caused by exposure to organic solvents and compared to controls. No difference in the concentration was found. Instead of using the platelet 5-HT concentration in the prediction of neurotoxic effects, the platelet 5-HT uptake rate may be an alternative parameter. A specific and sensitive double isotope derivative technique for 5-HT measurements is described. A solvent induced reduction in the number of platelets/ml platelet rich plasma was found and is discussed.

Toxicity study of di(2-ethylhexyl)phthalate (DEHP) in combination with acetone in rats.

In two separate studies with exposure duration 9 weeks or 4 weeks, male Wistar rats were dosed with di(2-ethylhexyl)phthalate (DEHP) by gavage and exposed to drinking water with or without acetone (0.5% wt/v in the 9-week study, 1.0% wt/v in the 4-week study). In the 9-week study the doses of DEHP were 0, 125, 250, 500 or 1000 mg/kg b.wt. In the 4-week study the doses of DEHP were increased to 1000, 5000 and 10,000 mg/kg b.wt. In the 9-week study, the relative liver weight was increased in the rats exposed to 500 and 1000 mg/kg b.wt. No interaction of DEHP and acetone was observed in any of the measured parameters. In the 4-week study DEHP, at the highest dose level, resulted in severe general toxicity. The group exposed to DEHP in combination with acetone was more affected. Male fertility was decreased. Body weight was decreased, and the relative weight of the liver, kidney, heart, brain and adrenals increased. The relative weight of the testes decreased in the 5000 and 10,000 mg/kg b.wt. groups. The weight of seminal vesicles and epididymals decreased at 10,000 mg/kg b.wt. In animals exposed to 5000 and 10,000 mg DEHP/kg b.wt. a severe atrophy of the seminiferous tubules and a slight diffuse Leydig's cell hyperplasia was observed. The cellular debris and conglomerates of desquamated cells found in the lumen of the seminiferous tubules were immunostained positive for vimentin. This indicates that Sertoli cell cytoplasm is included in the conglomerates an interesting finding not previously described. No specific interaction of DEHP and acetone was observed in any of the measured parameters.

Behavioural effects in rats after prenatal exposure to dearomatized white spirit.

The purpose of the study was to investigate the potential developmental neurotoxicity of the widely used organic solvent, white spirit. Rats (Mol:WIST) were exposed to 0 or 800 ppm dearomatized white spirit for 6 hr per day on gestation days 7-20. Developmental and neurobehavioural effects in the offspring were investigated using a test battery including assessment of physical development, reflex ontogeny, motor function, motor activity and, learning and memory. No significant effects were recorded on motor function and the activity in Open Field. In the initial learning period (age 1 month), the performance in a Morris water maze was similar in exposed and control animals. When testing for memory at the age of 2 months, the exposed male offspring used more time to locate the hidden platform. After platform relocation, impaired cognitive function was revealed in the exposed females. At the age of 5 months, learning and memory deficits were observed in exposed offspring. The differences were not related to poorer swimming capabilities, because swim speeds were similar to control values. The results show that prenatal exposure to 800 ppm white spirit caused long-lasting learning and memory deficits in rats.