Interactive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and retinoids on proliferation and differentiation in cultured human keratinocytes: quantification of cross-linked envelope formation

 Dioxins are potent inducers of chloracne in humans. This skin aberration can be interpreted as an altered differentiation pattern of acinar sebaceous base cells and a change in the rate of terminal differentiation of the keratinocytes. We measured this rate induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in primary cultures of human keratinocytes. As parameters for differentiation, we quantified the ³⁵S-methionine incorporation into cross-linked envelopes (revealing the total CLE biomass), as well as the number of microscopically visible CLEs. It was shown that TCDD is a very potent inducer of both CLE biomass and number with a half-maximal effect concentration (EC₅₀) of 1.4 nM. CLE biomass was maximally increased 10-fold and the number of cells in culture producing a CLE was increased from 15% in control cultures to maximally 75% of the cells in TCDD-treated cultures. Both effects were Ca²⁺-dependent and increased with elevated cell density, being optimal in post-confluent cultures. Retinoic acid dose-dependently decreased the effect of 10^-8 M TCDD, 10^-6 M having a nearly complete antagonistic action. This interaction of retinoic acid with TCDD-induced differentiation was non-competitive. Retinol was equally potent as an antagonist of the TCDD-induced elevation of CLE formation as compared with retinoic acid. Retinyl palmitate and etretinate were not very effective as TCDD antagonists. Supplementation of hydrocortisone suppressed the TCDD-induced keratinocyte differentiation. It was concluded that CLE biomass quantification provides a reliable and sensitive parameter for keratinocyte differentiation. In this in vitro system it is shown that TCDD strongly induces a switch from proliferation to terminal differentiation and that this effect can be antagonized effectively by retinoic acid and retinol. Received: 30 June 1994/Accepted: 20 October 1994     

Toxicity of β-blockers in a rat whole embryo culture: concentration-response relationships and tissue concentrations

Beta-adrenoceptor blockers are widely used drugs for the treatment of cardiovascular diseases. Since β-blockers cross the placenta, it is essential to consider possible adverse effects on the embryo. Six β-adrenoceptor blockers were tested at various concentrations (10 – 5000 μM) in a rat whole embryo culture. Although inducing a very similar pattern of dysmorphogenetic effects (incomplete flexure, disturbed development of the neural tube, the head, the heart and the tail bud), the compounds exhibited a wide range of embryotoxic potency. Estimation of the EC₅₀ (median-concentration producing dysmorphogenesis in 50% of the embryos) for the six compounds revealed differences of more than two orders of magnitude: propranolol 25 μM, alprenolol 30 μM, metoprolol 100 μM, pindolol 150 μM, acebutolol 500 μM, atenolol 4000 μM. Measurements of the concentrations of the various drugs in the cultured embryos at corresponding EC₅₀ levels showed differing values: metoprolol 4.5 μM, propranolol 5.2 μM, alprenolol 8.4 μM, pindolol 9.0 μM, acebutolol 12.5 μM and atenolol 77.0 μM. With regard to the EC₅₀ and the degree of substance transfer to the embryo it can be stated that propranolol and metoprolol show a much higher intrinsic potency to interfere with normal in vitro embryonic development than, e.g. atenolol. Received: 1 September 1993 / Accepted: 16 February 1994     

2-Acetylaminofluorene inhibits the activation of immune responses by blocking cell cycle progression at G1 phase

 2-Acetylaminofluorene (AAF) inhibited in a dose dependent manner mouse spleen cell blastogene sis in response to phorbol 12-myristate 13-acetate (PMA)/Ionomycin (Io) activation, the T-cell lectin, concanavalin A (Con A), and following stimulation by alloantigens as measured by the mixed lymphocyte response (MLR). AAF also markedly suppressed the T-cell dependent antibody forming cell (AFC) response to sRBC. AAF was most inhibitory on both the sRBC IgM AFC response and Con A stimulated proliferation when added during the first 24 h following initiation of culture. Direct addition of high concentrations of AAF (100 μM) to spleen cell cultures at 48 h following Con A stimulation produced a very modest inhibition (<20%) of T-cell proliferation as compared to 90% when added at the time cultures were initiated. Similarly, AAF (75 and 100 μM) produced a greater than 80% inhibition of the in vitro AFC response when spleen cells were sensitized with antigen in presence of AAF. In contrast, no inhibition of the IgM AFC response was produced when AAF (75 μM) was added to spleen cell cultures 48 or 72 h after antigen sensitization. Con A-triggered cell-cycle progression was attenuated at the G₁ stage by the addition of AAF (50 and 100 μM) with no inhibition of S to G₂/M phase transition. These results suggest that the mechanism of AAF-mediated immune suppression is through a blockade of cell cycle progression from G₁ to S phase. Received: 5 July 1994/Accepted: 19 October 1994     

Effects of harmine on dopamine output and metabolism in rat striatum: role of monoamine oxidase-A inhibition

In vivo microdialysis was used to investigate the effects of acute injections of harmine on extracellular concentrations of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxindoleacetic acid (5-HIAA) in the striatum of awake rats. Administration of harmine in doses of 0.5, 2.5, and 10 mg/kg (i.p.) elicited a dose-dependent increase of the dopamine efflux to 152, 173, and 243% and a decrease in DOPAC to 52, 36, and 10%, and HVA to 67, 45, and 20% throughout, respectively; 5-HIAA concentrations were decreased to 81, 74, and 72% only. In contrast to D-amphetamine, which also increases dopamine release and decreases its metabolites, the stimulatory action of harmine on dopamine release in the striatum was totally abolished in the presence of tetrodotoxin (1 microM). Similar to monoamine oxidase (MAO)-A inhibitors, harmine potentiated the stimulatory effect of D-amphetamine (10 microM), infused by reverse microdialysis in the striatum, on dopamine release. Pre-treatment with the benzodiazepine receptor antagonist flumazenil (5 mg/kg, i.p.) did not modulate the effect of harmine on striatal dopamine release and metabolism. Administration of the reversible MAO-A inhibitor, moclobemide (20 mg/kg, i.p.), induced an increase in dopamine to 256% and a decrease in DOPAC, HVA, and 5-HIAA to 30, 24, and 62%, respectively, reproducing a pattern similar to that of harmine. Taken together, these results indicate that harmine affects the brain dopamine system probably by acting as a MAO-A inhibitor and not as an inverse agonist for the benzodiazepine receptors.     

Toxicity of aflatoxin B1 in rat and mouse hepatocytes in vivo and in vitro

The reported LD50 for the adult, male Fisher rat is 1.2 mg aflatoxin B1/kg body weight (i.p.); we have found that male C57BL/6 mice survive single doses of aflatoxin B1 as high as 60 mg/kg (i.p.). We have demonstrated a 1000-fold greater LC50 of aflatoxin B1 for primary mouse liver cell cultures from C57BL/6 male mice (3 X 10(-5) M) than for primary liver cells from F344 male rats (3 X 10(-8) M). In 4 h of exposure to a non-toxic dose (1 X 10(-9) M) of [3H]aflatoxin B1, cultured rat liver cells accumulated up to 5-fold higher concentrations of 3H label than did mouse liver cells. The difference in cell-associated counts was due largely to higher levels of aflatoxin B1 metabolites bound to macromolecules in the rat cells.     

Dopaminergic system activity and cellular defense mechanisms in the striatum and striatal synaptosomes of the rat subchronically exposed to manganese

In 6-month-old male Wistar rats, levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), ascorbic acid (AA), dehydroascorbic acid (DHAA), uric acid and glutathione (GSH) were determined by HPLC in the striatum and striatal synaptosomes after subchronic oral exposure to MnCl₂ 50 – 100 – 150 mg/kg. Mn significantly decreased levels of DA and GSH and increased levels of DHAA and uric acid both in the striatum and synaptosomes. In synaptosomes, individual total Mn doses/rat were directly correlated with individual DOPAC/DA ratio values (r = +0.647), uric acid (r = +0.532) and DHAA levels (r = +0.889) and inversely correlated with DA (r = –0.757) and GSH levels (r = –0.608). In turn, GSH levels were inversely correlated with uric acid (r = –0.451) and DHAA levels (r = –0.460). In conclusion, the response of striatal cellular defense mechanisms (increase in AA oxidation, decrease in GSH levels) correlated well with changes in markers of dopaminergic system activity and increase in uric acid levels. The latter provides evidence of an Mn-induced oxidative stress mediated by xanthine oxidase. Received: 21 February 1994/Accepted: 18 April 1994     

Investigation of potential oncogenetic effects of β-cyclodextrin in the rat and mouse

 The results of oncogenicity studies of β-cyclodextrin in inbred Fischer 344 rats and CD-1 outbred mice are presented. Chronic feeding of β-cyclodextrin to Fischer 344 rats and CD-1 mice did not cause any treatment related carcinogenic effects. The only toxic effect was seen in mice as macroscopic distension of the large intestine with soft or fluid contents, histologically associated with the mucosa covered by mucous secretion containing exfoliated cells, and mucosal flattening and intestinal gland atrophy. Despite these observations, no differences between control and treated groups were observed concerning mortality, clinical observations or body weight and food consumption. Received: 14 November 1994/Accepted: 18 January 1995     

Quinolone-induced cartilage lesions are not reversible in rats

 The reversibility of quinolone-induced cartilage lesions has not been studied in detail. We treated five groups of five to seven juvenile Wistar rats (male and female; age: 5 weeks) with 2×600 mg ofloxacin/kg by gastric intubation on 1 day only (9:00 a.m. and 5:00 p.m.) and studied the knee joints histologically 3 days, 1, 3, 8 and 17 weeks later. In addition, joint cartilage specimens from vehicle-treated control rats (n=21) at corresponding age were examined. Cartilage lesions such as matrix swelling, loss of proteoglycans and horizontal clefts were found in nearly all knee joints (26 of 27 joints; incidence: 96%) of the ofloxacin-treated rats. Within the observation period of 4 months the size of these lesions in knee joint cartilage did not decrease significantly. The diameter of the lesions at the time points of evaluation was 1146±535, 1713±309, 1250 ±585, 1406±356, and 1542±467 μm, respectively (mean values±sd). Chondrocyte clusters producing glycosaminoglycans were observed 3 weeks after dosing and at later time points. They are considered to reflect the onset of repair but chondrocyte organization did not normalize during the study period, thus indicating the irreversibility of the effect under the experimental conditions. In principle, long-term joint cartilage damage has to be taken into account when the use of quinolones in children is considered. More detailed pharmacokinetic data are necessary for a reasonable risk assessment approach. Received: 28 August 1995/Accepted: 14 November 1995     

Toxicity and cytotoxicity of nigrin b, a two-chain ribosome-inactivating protein from Sambucus nigra : comparison with ricin

Nigrin b, a lectin isolated from the bark of elderberry (Sambucus nigra L.), has structure and enzymatic activity similar to that of ricin and other type 2 ribosome-inactivating proteins (RIPs), and yet is much less toxic to cells and animals. In an attempt to explain this difference, we studied (1) the cytotoxicity of both lectins at 18 and 37 °C, and in the presence of substances interfering with intracellular routing, and (2) the binding of nigrin b to, and its uptake and degradation by HeLa cells, in parallel with ricin. As compared with the latter, (1) less nigrin b was bound and more was degraded by cells, with a resulting lower concentration remaining inside the cells, and (2) there is evidence for a different intracellular routing followed by the two lectins. These results may explain at least partly the different cytotoxicity and consequently the lower toxicity to mice of nigrin b compared with ricin. Received: 5 September 1996 / Accepted: 30 October 1996     

Effects of veniafaxine in the sleep architecture of rats

 Different venlafaxine doses (1, 5, and 10 mg/kg) and saline solution were administered to ten male Wistar rats (Latin-Square design). Compared with saline, venlafaxine produced a dose-related supression of REM sleep and an increase in wake time while slow wave sleep was reduced. This effect is similar to the one that has been reported with some tricyclic antidepressants. Received: 31 July 1996 / Final version: 5 November 1996     

Comparing the reinforcing efficacy of nicotine containing and de-nicotinized cigarettes: a behavioral economic analysis

Rationale: Smoking-related respiratory stimuli produced by de-nicotinized cigarettes may function as conditioned reinforcers, but behavioral data on such reinforcing effects are limited. Objectives: The present experiment compared the reinforcing efficacy of cigarettes that provided only smoking-related stimuli (de-nicotinized cigarettes) and cigarettes that provided both smoking-related stimuli and nicotine. Methods: Eight human subjects responded on a progressive-ratio schedule in which the number of plunger pulls required for standardized cigarette puffs increased across sessions. In one phase, the breakpoints, number of puffs earned per session, peak response rates, ratio producing peak response rates, and the elasticity of demand for cigarette puffs were compared for nicotine-containing and de-nicotinized cigarettes when each cigarette type was the only one available. In another phase, subjects chose between the two cigarette types at some of the prices examined in the previous phase. Results: Nicotine-containing and de-nicotinized cigarettes produced similar measures of reinforcing efficacy when each was presented alone, but there was a strong preference for nicotine-containing cigarettes when subjects were given a choice. Conclusions: These data support suggestions that smoking-produced sensory stimuli may function as conditioned reinforcers and that the relative reinforcing efficacy of cigarettes is determined by the combined effects of the nicotine/conditioned reinforcing complex provided by smoking. Received: 15 March 1999 / Final version: 21 June 1999     

Influence of glucose on the toxicity of oxophenylarsine in MDCK cells

 Trivalent arsenicals like oxophenylarsine (PhAsO) inhibit cellular pyruvate dehydrogense, thus leading to a drop of acetylCoA formation and a slow-down of the citric acid cycle. Glucose may protect cells from arsenic toxicity, because increased glycolysis may prevent fatal shortage of ATP. On the other hand, PhAsO has been shown to inhibit glucose uptake in Madin-Darby canine kidney (MDCK) cells. We have investigated the effect of PhAsO on viability, ATP levels and glucose uptake of MDCK cells in the presence of normal (5 mmol/l) and low (0.01 mmol/l) glucose concentrations. At normal as well as at low glucose concentrations, cell viability as assessed by formazan formation was not affected by PhAsO concentrations up to 2 μmol/l within 3 h of observation. At higher PhAsO concentrations viability was diminished earlier and more pronounced in the presence of low glucose concentrations. 10 μmol/l PhAsO induced a drastic drop of ATP within 30 min which was followed by an almost complete loss of viable cells after 180 min in the presence of low glucose concentrations, while at normal glucose levels no influence on ATP contents or on cell viability was detected within 60 min of incubation. On the other hand, glucose uptake, determined as ¹⁴C accumulation by cells incubated for 10 min with D[6-¹⁴C]-glucose, was inhibited by PhAsO at low as well as at normal glucose concentrations in a dose dependent manner. At normal glucose concentrations, however, basal uptake was higher (57 nmol/mg protein) and half-maximum inhibition (IC₅₀) was shifted to higher PhAsO concentrations (2×10^-4 mol/l) than at low glucose levels (basal uptake: 1.6 nmol/mg protein; IC₅₀: 5×10^-5 mol/l). It is concluded that 1) in PhAsO-exposed MDCK cells different uptake mechanisms operate in high and low glucose states and 2) that glucose exerts a beneficial effect on the toxicity of PhAsO in these cells. Received: 22 August 1994 / Accepted: 6 December 1994     

Effects of benzodiazepine agonists on punished responding in pigeons and their relationship with clinical doses in humans

 Anxiolytic drugs generally produce anticonflict effects in both pigeons and rats, although relatively few anxiolytics have been examined in the pigeon and the procedure has not been as completely validated as the rat model. In this study, we examined the antipunishment effects of a variety of benzodiazepine agonists in pigeons and compared the relationship between their potencies to engender anxiolytic-like effects and their clinical doses in humans. In pigeons whose responding was maintained under a multiple FR30^food:FR30^food+shock schedule, the benzodiazepine agonists diazepam, flunitrazepam, alprazolam, chlordiazepoxide, lorazepam, flurazepam, bromazepam, medazepam, and clorazepate produced dose-related increases in punished responding, and, with the exception of medazepam, decreased unpunished responding at higher doses. Potencies calculated from the percentage of pigeons showing significant increases in punished responding ranged from 0.081 to 11 mg/kg, and these potencies were invariably lower than those for decreases in unpunished responding by factors ranging from 2.2 to more than 14. The comparison of relative potencies of benzodiazepine receptor agonists in pigeons and humans revealed a high positive correlation (0.90, P<0.005), thus demonstrating the predictive validity of this preclinical animal model for anxiolytic benzodiazepines. The results agree with previous findings of robust anticonflict effects of benzodiazepine receptor agonists and extend further the pharmacological characterization to compounds that have not been examined previously in pigeons. Received: 22 May 1998 / Final version: 4 August 1998     

Assessment of primary neuronal culture as a model for soman-induced neurotoxicity and effectiveness of memantine as a neuroprotective drug

 An in vitro mammalian model neuronal system to evaluate the intrinsic toxicity of soman and other neurotoxicants as well as the efficacy of potential countermeasures was investigated. The link between soman toxicity, glutamate hyperactivity and neuronal death in the central nervous system was investigated in primary dissociated cell cultures from rat hippocampus and cerebral neocortex. Exposure of cortical or hippocampal neurons to glutamate for 30 min produced neuronal death in almost 80% of the cells examined at 24 h. Hippocampal neurons exposed to soman for 15–120 min at 0.1 μM concentration caused almost complete inhibition (≥90%) of acetylcholinesterase but failed to show any evidence of effects on cell viability, indicating a lack of direct cytotoxicity by this agent. Acetylcholine (ACh, 0.1 mM), alone or in combination with soman, did not potentiate glutamate toxicity in hippocampal neurons. Memantine, a drug used for the therapy of Parkinson’s disease, spasticity and other brain disorders, significantly protected hippocampal and cortical neurons in culture against glutamate and N-methyl-D-aspartate (NMDA) excitotoxicity. In rats a single dose of memantine (18 mg/kg) administered 1 h prior to a s.c. injection of a 0.9 LD₅₀ dose of soman reduced the severity of convulsions and increased survival. Survival, however, was accompanied by neuronal loss in the frontal cortex, piriform cortex and hippocampus. Received: 2 May 1994 / Accepted: 9 November 1994     

Selective impairment in the recognition of anger induced by diazepam

Rationale: Facial expressions appear to be processed by at least partially separable neuro-cognitive systems. Given this functional specialisation of expression processing, it is plausible that these neurocognitive systems may also be dissociable pharmacologically. Objective: The present study therefore compared the effects of diazepam (15 mg) with placebo upon the ability to recognise emotional expressions. Methods: A double blind, independent group design was used to compare the effects of diazepam and matched placebo in32 healthy volunteers. Participants were presented morphed facial expression stimuli following a paradigm developed for use with patients with brain damage and asked to name one of the six basic emotions (sadness, happiness, anger, disgust, fear and surprise). Results: Diazepam selectively impaired subjects’ ability to recognise angry expressions but did not affect recognition of any other emotional expression. Conclusions: The findings are interpreted as providing further support for the suggestion that there are dissociable systems responsible for processing emotional expressions. It is suggested that these findings may have implications for understanding paradoxical aggression sometimes elicited by benzodiazepines. Received: 27 May 1999 / Accepted: 7 July 1999     

Use of dantrolene in experimental scorpion envenomation by Androctonus Australis Hector

 Hyperthermia and profuse perspiration are rarely absent in severe cases of scorpion envenomation. Based on these observations, the aim of this study was to determine the therapeutic effects of dantrolene, on experimental poisoning by the venom of Androctonus australis hector. Dantrolene is a directly acting muscle relaxant which lowers the body temperature in malignant hyperthermia. The results indicate that the early use of this drug raises the LD₅₀ in experimentally poisoned mice. If these results are transposable to humans, dantrolene could be a useful therapeutic adjuvant. Received: 3 November 1994/Accepted: 5 January 1995     

Colchicine enhances intestinal permeability in patients with familial Mediterranean fever

Objective: Colchicine therapy is complicated by frequent gastrointestinal adverse effects. Methods: We compared intestinal permeability in 21 patients with familial Mediterranean fever on long-standing colchine therapy (mean 5.8 years) and significant gastrointestinal complaints and 12 untreated patients and 14 healthy volunteers. The double probe (lactulose/mannitol) permeability test was performed using a hyperosmolar test solution (1580 mosmol) and the differential urinary recovery ratios were calculated. Results: Familial Mediterranean fever patients on colchicine therapy had significantly higher lactulose/mannitol urinary excretion ratios (0.073) compared to untreated patients (0.035) and to healthy controls (0.021). Untreated familial Mediterranean fever patients had significantly greater urinary lactulose/mannitol recovery ratios than controls (P < 0.02). No correlation was found between the degree of enhanced permeability and the length of exposure to the drug or the severity of clinical symptoms. Conclusion: Intestinal permeability was significantly enhanced in patients with familial Mediterranean fever treated with colchicine. Received: 19 February 1996/Accepted in revised form: 9 July 1996     

Dopamine-transporter occupancy after intravenous doses of cocaine and methylphenidate in mice and humans

Objectives: Recent studies using positron emission tomography (PET) have established the relationship between an intravenous dose of cocaine and the percentage occupancy of the dopamine transporter in humans, and have documented the requirement of more than 50% occupancy for perception of the ”high”. The present experiments were conducted to examine dose–occupancy and dose–effect relationships in mice for cocaine and also for methylphenidate, a dopamine uptake blocker used in pediatric psychiatry. Methods: Percentage occupancies of the dopamine transporter by cocaine and methylphenidate were estimated after intravenous injection in mice from the displacement of in vivo binding of [³H]cocaine from the striatum. Locomotor activity was measured in a photocell apparatus. Results: The relationship between drug doses (milligrams of hydrochloride salt per kilogram body weight) and percentage occupancy of the dopamine transporter was indistinguishable for cocaine and methylphenidate, and corresponded to about 50% occupancy at 0.25 mg/kg and about 80% at 1 mg/kg. This was similar to the relationship between drug dose and transporter occupancy, previously measured in human and baboons using [¹¹C]cocaine or [¹¹C]d-threo-methylphenidate and PET. Methylphenidate increased locomotor activity in the mice substantially more than cocaine at the same dose and the same degree of dopamine-transporter receptor occupancy. Conclusions: The range of dopamine-transporter occupancy required for behavioral activation in the mice was thus similar to that previously reported for experience of a cocaine- or methylphenidate-induced ”high” in human subjects. Our results are consistent with other studies in which both cocaine and methylphenidate were evaluated in animal behavioral assays and were found to have very similar psychopharmacological properties. Received: 17 February 1999 / Final version: 17 April 1999     

A morphological analysis of the short-term effects of benzene on the development of the hematological cells in the bone marrow of mice and the effects of interleukin-1α on the process

 Chronic exposure of humans to benzene (BZ), a widely used industrial chemical and a ubiquitous environmental pollutant, causes aplastic anemia and acute myeloid leukemia. The purpose of the studies reported here was to determine whether the observed depression of bone marrow (BM) cellularity in mice administered benzene was reflected in a suppression of development of all of the hematopoietic lineages and to confirm the ability of interleukin-1α (IL-1α) to prevent BZ-induced BM cell depression. We report that BZ, administered twice per day for 2 days to C57Bl/6J mice at a dose of 600 mg/kg body weight, caused a significant depression of the total number of nucleated BM cells per femur when measured on day 3. The observed depression reflects a complex situation that represents the net effect of a decrease in the total number of cells of the lymphocytic and erythroid lineages, along with an increase in the number of intermediate and terminally differentiated cells of the granulocytic lineage. An experiment to monitor the effects of BZ over a 7-day period showed a progressive depressive effect on the lymphocytes and an initial depression of the erythroid cells at day 3 that remained constant until day 7. Conversely, the numbers of intermediate and terminally differentiated granulocytes progressively increased over the 7 days. The BM appeared to recover from the depressive effects of BZ immediately upon cessation of exposure, as the number of nucleated BM cells began to rise by day 5 and was equal to that of the control group by day 7. The results expand our earlier finding (Renz and Kalf 1991) that the overall depression of BM cellularity occurs because of an inability of the stromal fibroblast to produce colony-stimulating factors essential for stem and progenitor cell survival. This results from inhibition by the BZ metabolite, hydroquinone (HQ), of the processing of pre-IL-1α to the mature cytokine. The ability of exogenously administered biologically active, but not heat inactivated, recombinant IL-1α to prevent BZ-induced depression of total BM cellularity as a function of dose, when added concomitantly with BZ, and to augment the recovery from BZ exposure up to day 5 supports this hypothesis. IL-1α administered alone showed no effect on the total number of nucleated cells in the BM; however, analysis of its effects on the cells of the various lineages indicated that lymphocytes were unaffected, nucleated erythroid cell were decreased and the immature and mature granulocytic forms were increased. It is of interest that granulopoiesis is not decreased during BZ-induced inhibition of IL-1α production, but rather significantly stimulated. Received: 6 June 1994/Accepted: 10 August 1994     

Protective effect of vitamin E on chromium (VI)-induced cytotoxicity and lipid peroxidation in primary cultures of rat Hepatocytes

Pretreatment of primary cultures of rat hepatocytes with α-tocopherol succinate (vitamin E) for 20 h prior to exposure to K₂Cr₂O₇ resulted in a marked decrease of chromium (VI)-induced cytotoxicity, as evaluated by the leakage of lactate dehydrogenase, without affecting cellular uptake and subcellular distribution of chromium. The levels of chromium (VI)-induced lipid peroxidation, as monitored by malondialdehyde formation, were also inhibited by pretreatment with the vitamin. Pretreatment with vitamin E normalized the levels of nonenzymatic antioxidants such as glutathione and vitamin C suppressed by dichromate, and caused a distinct accumulation of vitamin E in hepatocytes. However, vitamin E pretreatment did not affect the activities of enzymatic antioxidants including glutathione reductase, superoxide dismutase, and catalase suppressed by dichromate. These results indicate that the protective effect of vitamin E against chromium (VI)-induced cytotoxicity as well as lipid peroxidation, may be associated more with the level of nonenzymatic antioxidants than the activity of enzymatic antioxidants. Received: 31 October 1995/Accepted: 16 July 1996