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At least 19 recordsLinked to original sources

PubMed1978

Oral toxicity of ferric dimethyl-dithiocarbamate (ferbam) and tetramethylthiuram disulfide (thiram) in rodents.

Single oral doses of ferbam, thiram, zineb, or maneb produced central nervous system stimulation followed by depression and alopecia. Ferbam and thiram were more toxic on the basis of weight than zineb; maneb was relatively nontoxic. There was no species difference in acute toxicity between rats and mice. In 13- and 80-wk feeding studies, the toxic effects of ferbam and thiram in rats were similar; however, thiram was more toxic on the basis of weight than ferbam. During the 80-wk feeding study, weight gain was reduced in ferbam-treated rats starting at daily doses of 8 mg/kg in males and 37 mg/kg in females and in thiram-treated rats staring at daily doses of 5 mg/kg in males and 26 mg/kg in females. Food consumption was reduced in proportion to the reduced weight gain. Death occurred in males fed 109 or 331 mg/kg.d ferbam and in males fed 58 or 132 mg/kg.d thiram. Female rats fed 96 mg/kg.d ferbam or 67 mg/kg.d thiram developed alopecia and ataxia, which led to paralysis of the hind limbs. Male rats fed ferbam or thiram had a more severe incidence of squamous metaplasia in the thyroid and fatty infiltration in the pancreas than control males. Ferbam or thiram reduced the incidence of spontaneous nephritis in both males and females. The male rats that were fed 109 or 331 mg/kg.d ferbam and died betweeen 1 and 5 wk had golden pigment in the reticuloendothelial cells of the spleen and in the enlarged mesenteric lymph nodes, associated with hemosiderosis. Moderate tubular degeneration of the testes with atypical spermatids in the epididymis occured in some rats fed 132 mg/kg.d thiram for 13 wk but not in rats fed up to 52 mg/kg.d for 80 wk. Periodic hematologic examination and terminal clinical blood tests did not reveal any severe changes. Ferbam and thiram did not alter the occurrence or latent period of the spontaneous tumors seen in control rats.

Animal Feed↗

PubMed2001

An evaluation of thiram toxicity on cultured human skin fibroblasts.

Thiram is widely used in agriculture as a fungicide and, to a lesser extent, as a vulcanizing agent in the rubber industry. In spite of the extensive use of thiram, knowledge on its toxicity and health risk remains limited, and few investigations have been performed to assess specific damage at the cellular and subcellular level. We report here the cytotoxic effects of thiram on cultured human skin fibroblasts. Our results demonstrated that thiram exposure induced a dose- and time-dependent decrease in the viable cell recovery with 100% cell death observed with a concentration of 5.0 mg/l. As judged by morphological changes and biochemical criteria, thiram-mediated cell death was not of the apoptotic but seemed to be of the necrotic type. This cell death was not associated with a modification of gene expression of different constituents of the extracellular matrix. A late increase of lactate production was evident after thiram treatment, suggesting a mitochondrial metabolic pathway dysfunction as reported by other authors using similar compounds. However, this phenomenon appeared as a secondary response to the toxic action of thiram. The cytotoxic effect of thiram is possibly due to an oxidant effect inherent to the structure of thiram and the interaction between thiram and vital cellular molecules.

Adult↗

PubMedDate not supplied

Characterization of pregnancy outcome following thiram-induced ovulatory delay in the female rat.

A single injection of the dithiocarbamate fungicide, thiram, suppresses the proestrous surge of LH and delays ovulation for 24 h. In this study, we examined fertility after a thiram-induced delayed ovulation. Females were injected with thiram (50 mg/kg, IP) on proestrus (1300 h) and mated on the following evening. Control and thiram-treated, but nondelayed, females were injected and mated on the same day. The number of females in the thiram-delayed group that became pregnant was reduced and litter size on GD 20 was reduced: however, no obvious morphological anomalies were seen. The number of pregnant females and litter size was not altered in the thiram-nondelayed rats, indicating that it is the thiram-induced delay in ovulation and not the exposure to thiram per se that was responsible for altered pregnancy outcome. On GD 7 and 11, the number of live fetuses per litter was reduced in the delayed females, but the number of implantation sites was not different from controls. On GD 11 the mean developmental score, head length, crown-rump length, and somite number in the delayed group were also reduced, indicating retarded development of live embryos. These results demonstrate that delayed ovulation induced by a single thiram exposure does not alter the number of oocytes released or the number that implant. However, the concept from these females are compromised during midgestation.

Animals↗

PubMed2002

Thiram inhibits angiogenesis and slows the development of experimental tumours in mice.

Thiram-tetramethylthiuram disulphide--a chelator of heavy metals, inhibited DNA synthesis and induced apoptosis in cultured bovine capillary endothelial cells. Bovine capillary endothelial cells were 10-60-fold more sensitive to thiram than other cell types. These effects were prevented by addition of antioxidants, indicating involvement of reactive oxygen species. Exogenously added Cu2+ impeded specifically and almost completely the inhibitory effect of thiram for bovine capillary endothelial cells. Moreover, thiram had markedly inhibited human recombinant Cu/Zn superoxide dismutase enzymatic activity (85%) in vitro. Moreover, PC12-SOD cells with elevated Cu/Zn superoxide dismutase were less sensitive to thiram treatment than control cells. These data indicate that the effects of thiram are mediated by inhibition of Cu/Zn superoxide dismutase activity. Oral administration of thiram (13-30 microg mouse(-1)), inhibited angiogenesis in CD1 nude mice. Tumour development is known to largely depend on angiogenesis. We found that oral administration of thiram (30 microg) to mice caused significant inhibition of C6 glioma tumour development (60%) and marked reduction (by 3-5-fold) in metastatic growth of Lewis lung carcinoma. The data establish thiram as a potential inhibitor of angiogenesis and raise the possibility for its use as therapy in pathologies in which neovascularisation is involved, including neoplasia.

Administration, Oral↗

PubMed2005

Changes in the tibial growth plates of chickens with thiram-induced dyschondroplasia.

Tibial dyschondroplasia (TD) is a metabolic cartilage disease of young poultry in which endochondral bone formation is disrupted leading to the retention of a non-calcified, avascular plug of cartilage in the tibial growth plate. Chicks aged 7 days were fed either a control diet or one containing thiram 100 ppm for 48 h to induce TD. Cell multiplication in the growth plate was determined thereafter with bromodeoxyuridine (BrdU) labelling, and metabolic changes by measuring alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), and glutathione (GSH) activities. The effect on chondrocyte maturation was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of gene expression. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and DNA fragmentation were used to determine the effects of thiram on cell survival. The results showed that thiram-induced TD was not due to the multiplication of cells in the post-proliferative zones. Thiram did not affect ALP activity, which would have indicated a loss of calcification potential, but it reduced both TRAP and the glutathione concentrations, suggesting that the growth plate metabolism and remodelling functions were adversely affected. Thiram appeared to have no effect on the expression of type X collagen, transglutaminase, RUNX2, or matrix metalloproteinase-2 (MMP) genes suggesting that it did not alter the maturation potential of chondrocytes. On the contrary, the expressions of MMP-13 and vascular endothelial growth factor (VEGF) genes were "up-regulated," suggesting that thiram has pro-angiogenic activity. However, TUNEL assay showed that thiram induced endothelial cell apoptosis in the capillary vessels of the growth plates, as early as 10 days of age, when TD was not visually evident. The vascular death increased on subsequent days accompanied by massive death of chondrocytes in the transition zone of the growth plate. The induction of apoptosis in the growth plate was also demonstrated by DNA fragmentation. It was concluded that thiram induced TD not through an increase in the multiplication of chondrocytes in the transition zone and not by altering the expression of genes causing the arrest of chondrocytes in a prehypertrophic state, but by creating a metabolic dysfunction which led to the destruction of blood capillaries in the transition zone chondrocytes.

Acid Phosphatase↗

PubMed2001

Thiram-induced cytotoxicity is accompanied by a rapid and drastic oxidation of reduced glutathione with consecutive lipid peroxidation and cell death.

The toxic effect of thiram, a widely used dithiocarbamate fungicide, was investigated in cultured human skin fibroblasts. Cell survival assays demonstrated that thiram induced a dose-dependent decrease in the viable cell recovery. Thiram exposure resulted in a rapid depletion of intracellular reduced glutathione (GSH) content with a concomitant increase in oxidized glutathione (GSSG) concentration. Alteration of glutathione levels was accompanied by a dose-dependent decrease in the activity of glutathione reductase (GR), a key enzyme for the regeneration of GSH from GSSG. Thiram-exposed cells exhibited increased lipid peroxidation reflected by enhanced thiobarbituric acid reactive substances (TBARS) production, suggesting that GSH depletion and the lower GR activity gave rise to increased oxidative processes. To investigate the role of decreased GSH content in the toxicity of thiram, GSH levels were modulated prior to exposure. Pretreatment of fibroblasts with N-acetyl-L-cysteine (NAC), a GSH biosynthesis precursor, prevented both lipid peroxidation and cell death induced by thiram exposure. In contrast, thiram cytotoxicity was exacerbated by the previous depletion of cellular GSH by L-buthionine-(S,R)-sulfoximine (BSO). Taken together, these results strongly suggest that thiram induces GSH depletion, leading to oxidative stress and finally cell death.

Acetylcysteine↗

PubMed1986

Metabolism of a dithiocarbamate fungicide thiram to carbon disulfide in the rat and its hepatotoxic implications.

Thiram, tetramethylthiuram disulfide, is used extensively as an agricultural fungicide whose toxicity is largely dependent on its metabolism. The following experiments were carried out to investigate whether carbon disulfide (CS2) is a metabolic product of microsomal monooxygenase catalyzed metabolism of thiram in rats. Adult male Sprague-Dawley rats (160-200 g) were given thiram (60 mg/kg, b.wt.) in corn oil by intraperitoneal injection and placed individually in a metabolic apparatus. Concentration of CS2 in the breath was determined by drawing the expired air through a series of traps containing a CS2 complexing agent. Expiration of CS2 was almost complete within 5 hrs following thiram administration. The formation of CS2 from thiram was increased by pretreatment of rats with phenobarbital and decreased by SKF 525-A. Furthermore, measurement of the activities of hepatic microsomal and serum enzymes at 5 hrs and 24 hrs following thiram treatment indicated that thiram caused significant loss of cytochrome P-450 and benzphetamine N-demethylase activity only at 24 hrs interval whereas there was significant elevation of sorbitol dehydrogenase (SDH) and serum glutamic oxalacetic transaminase (SGOT) activity at 5 and 24 hrs after treatment. The data confirm that CS2 is an in vivo metabolite of thiram and may be, in part, responsible for the observed hepatotoxicity.

Animals↗

PubMed2002

Effect of cytochrome P450 inducers on the metabolism and toxicity of thiram in rats.

Thiram is a dithiocarbamate compound widely used as an agricultural fungicide. This study examined the effect of cytochrome P450 (CYP) inducers on the metabolism and toxicity of thiram in rats. Rats were pretreated with 3-methyl cholathrene (3-MC), phenobarbital (PB), isoniazid (INH), or pregnenolone-16a-carbonitrile (PCN) as selective inducers of CYP 1A1, 2B1, 2E1 and 3A2, respectively. Thiram was administered ip to induced rats at 0.1 or 0.5 mmol/kg, and the animals were sacrificed 3 or 24 h later to assess P450 interaction and liver damage, respectively. No significant inhibition of 3-me-induced CYP1A1 was observed with either thiram dose at 3 or 24 h after treatment; similar results were noted for rats induced with PB or PCN. By contrast, when INH was the selective inducer of CYP2E1, there was significant inhibition by thiram 3 h and 24 h after treatment, suggesting that thiram was metabolized by the induced CYP2E1; there was a significant increase in ALT activity reflective of liver damage in the rats treated with thiram. The results suggest that CYP2EI induced by INH may be significantly involved in the metabolism of thiram, and the associated liver damage.

Alanine Transaminase↗

PubMed2000

Reasons for the decomposition of the fungicide thiram during preparation of fruit and vegetable samples and consequences for residue analysis.

The concentration of thiram in aqueous solution decreases by 50-75% within 20 min in the presence of cut pieces of apple, cucumber or celeriac with a section surface area of 160 cm2 each. The decomposition rate is predominantly influenced by the section surface area of the cut fruit and vegetable samples. Denaturing reaction conditions (exchange of the solvent water by methanol; boiling of sample material) will significantly slow down the decomposition rate. It was concluded that the thiram decomposition had been caused by enzymes on the section surface of the fruit and vegetable samples. For a specific determination of thiram, a simple rinsing of the intact fruit and vegetable material was appropriate as extraction method. For the screening of thiram residues, the often used Keppel method, which determines CS2 from thiram or dithiocarbamates seems to be applicable even if samples had been coarsely cut, since decomposition of the CS2-forming intermediates is slower than the breakdown of thiram itself. Therefore, specific determination of thiram is necessary only, if maximum residue limits for dithiocarbamates are not adhered to.

Antifungal Agents↗

PubMed1996

Carcinogenic and co-carcinogenic studies of thiram on mouse skin.

Thiram (tetramethyl thiuram disulfide), a carbamate fungicide, is used in the rubber processing industry as an accelerator and vulcanizing agent. Previous studies evaluated the tumorigenic potential of thiram in rodents, but failed to provide conclusive results. In the present study the tumorigenic potential of thiram was evaluated in Swiss albino mice by a two-stage initiation-promotion protocol and a long-term in vivo bioassay for carcinogenicity. Results revealed that following tumour initiation with thiram and promotion with 12-O-tetradecanoyl phorbol 13-acetate, skin tumours developed, mostly at the site of treatment (dorsal skin) in single and multiple dose-initiated animals. Similarly, papillomatous growths were observed on the dorsal skin of the mice initiated with a single subcarcinogenic dose of dimethylbenzanthracene and promoted with thiram. Thiram failed to provoke tumorigenesis when tested as a complete carcinogen for up to 52 wk and thereafter the study was terminated due to increased mortality. It is concluded that thiram has both tumour initiating and tumour-promoting potential in both sexes of Swiss albino mice following topical exposure at the tested dose level.

Administration, Topical↗

PubMedDate not supplied

The dithiocarbamate fungicide thiram disrupts the hormonal control of ovulation in the female rat.

Thiram has been reported to inhibit dopamine-beta-hydroxylase (D beta H), thereby affecting norepinephrine (NE) synthesis. Because NE is a neurotransmitter that is known to play an important role in the hypothalamic regulation of pituitary function, the acute effects of the thiram on the hormonal control of ovulation in the rat were investigated. Ovariectomized, estrogen-primed female rats were given a single injection of thiram (0, 6, 12, 25, 50, and 100 mg/kg, i.p.) at 1100 h and serum LH was measured in serial bleeds. Thiram at 100 and 50 mg/kg completely blocked the LH surge in all rats tested, while 12 and 25 mg/kg blocked the surge in 40 and 75% of the treated animals, respectively. Six mg/kg had no effect. Ovulation was then assessed in intact, proestrous females in response to thiram administration (0, 12, 25, or 50 mg/kg) at 0900, 1100, 1300, or 1800 h. Ovulation was blocked by 25 and 50 mg/kg at 1300 h in all rats, but when injected at 1100 h only the 50 mg/kg dose was effective. No such blockade was found with 50 mg/kg injected at 0900 and 1800 h. To assess the influence of thiram on the LH surge in intact rats, additional females were dosed at 1300 h on the day of proestrus and blood collected over that same day. Thiram at 50 mg/kg blocked the LH surge in all rats, while 25 mg/kg blocked the surge in 60% of the females tested. No effect occurred with 12 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2006

Reduction of glucocorticoid receptor ligand binding by the 11-beta hydroxysteroid dehydrogenase type 2 inhibitor, Thiram.

Endogenous and synthetic glucocorticoids (GCs), such as cortisol and dexamethasone (Dex), modulate airway inflammation, regulate the production of surfactant by lung epithelial cells, and influence fetal lung maturation. The 11-beta hydroxysteroid dehydrogenase type 2 (HSD2) enzyme catalyzes the oxidation of bioactive cortisol and Dex to their 11-keto metabolites. Thiram (tetramethylthiuram disulfide) specifically inhibits HSD2 activity by oxidizing cysteine residues located in the cofactor binding domain of the enzyme. During studies performed to define a potential role for HSD2 in modulating GC action in human lung epithelial cells, we observed that exposure of intact human lung epithelial cells (NCI-H441) to 50 microM Thiram significantly attenuated the down-stream effects of Dex (100 nM) on the expression of two GC-sensitive genes, pulmonary surfactant proteins A and B. This observation appeared to be inconsistent with simple inhibition of HSD2 activity. Although Thiram inhibited HSD2 oxidase activity in a dose-dependent manner without affecting HSD2 protein expression, Thiram also reduced specific binding of [3H]-Dex to the glucocorticoid receptor (GR). Pre-treatment of cells with 1 mM dithiothreitol (DTT), a thiol-reducing agent, completely blocked the inhibitory effect of Thiram on ligand binding. These results are suggestive that Thiram may alter the ligand-binding domain of the GR by oxidizing critical thiol-containing amino acid residues. Taken collectively, these data demonstrate that attenuated down-stream GC signaling, via decreased binding of ligand to the GR, is a novel cellular effect of Thiram exposure in human lung epithelial cells.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

PubMed2000

Hapten synthesis for the development of a competitive inhibition enzyme-immunoassay for thiram.

An enzyme-linked immunosorbent assay (ELISA) was developed for the fungicide thiram. Two types of haptens were synthesized. The first type exhibits the two symmetrical N-alkyl dithiocarbamate patterns of thiram with a spacer arm linked to one of the N-methyl terminal group. The second type exhibits one of the two symmetrical N-alkyl dithiocarbamate patterns of thiram with a variable-length spacer arm linked to one sulfur atom. Polyclonal antibodies suitable for thiram detection were obtained from immunization with an hapten of the first type, while haptens of the second type were used as coating antigens to develop a competitive ELISA against thiram. The IC(50) value for thiram was estimated to be 0.24 microg/mL, with a detection limit of 0.03 microg/mL. The assay seems to be thiram-specific since no or little cross-reaction with other dithiocarbamates were observed.

Binding, Competitive↗

PubMed1997

Thiram and dimethyldithiocarbamic acid interconversion in Saccharomyces cerevisiae: a possible metabolic pathway under the control of the glutathione redox cycle.

A rapid decrease of intracellular glutathione (GSH) was observed when exponentially growing cells of Saccharomyces cerevisiae were treated with sublethal concentrations of either dimethyldithiocarbamic acid or thiram [bis(dimethylthiocarbamoyl) disulfide]. The underlying mechanism of this effect possibly involves the intracellular oxidation of dimethyldithiocarbamate anions to thiram, which in turn oxidizes GSH. Overall, a linear relationship was found between thiram concentrations up to 21 microM and production of oxidized GSH (GSSG). Cytochrome c can serve as the final electron acceptor for dimethyldithiocarbamate reoxidation, and it was demonstrated in vitro that NADPH handles the final electron transfer from GSSG to the fungicide by glutathione reductase. These cycling reactions induce transient alterations in the intracellular redox state of several electron carriers and interfere with the respiration of the yeast. Thiram and dimethyldithiocarbamic acid also inactivate yeast glutathione reductase when the fungicide is present within the cells as the disulfide. Hence, whenever the GSH regeneration rate falls below its oxidation rate, the GSH:GSSG molar ratio drops from 45 to 1. Inhibition of glutathione reductase may be responsible for the saturation kinetics observed in rates of thiram elimination and uptake by the yeast. The data suggest also a leading role for the GSH redox cycle in the control of thiram and dimethyldithiocarbamic acid fungitoxicity. Possible pathways for the handling of thiram and dimethyldithiocarbamic acid by yeast are considered with respect to the physiological status, the GSH content, and the activity of glutathione reductase of the cells.

Cytochrome c Group↗

PubMed2003

Thiram and ziram stimulate non-selective cation channel and induce apoptosis in PC12 cells.

The neurotoxicity of dithiocarbamates has been previously reported, however, the detailed mechanism underlying the neurotoxicity is still not fully understood. Among the dithiocarbamates, we investigated thiram and ziram in a neuronal-like pheochromocytoma (PC12) cells. Thiram and ziram strongly induced cell death in both dose- and time-dependent manners with the LC(50) of 0.3 and 2 microM, respectively. The cell death showed typical apoptotic features, such as DNA fragmentation and an increase of subdiploidy nuclei. Interestingly, both thiram and ziram induced rapid and sustained increases of intracellular Ca(2+) in PC12 cells, which were almost completely blocked by flufenamic acid (FFA), an inhibitor of non-selective cation channel. BAPTA-AM, an intracellular Ca(2+) chelator, inhibited the thiram- and ziram-induced apoptotic cell death. These results suggest that thiram and ziram induce apoptotic neuronal cell death by Ca(2+) influx through non-selective cation channels. The present study may provide a clue for understanding the mechanism of neurotoxicity of thiram and ziram.

Animals↗

PubMed1980

Dietary no-effect level of a dithiocarbamate fungicide, thiram, evaluated from measurement data on rats. I. Choice of the model of the dose-response relationship.

Rats were fed diets containing various amounts of added thiram, a dithiocarbamate fungicide. As thiram feeding resulted in decreased appetite, control rats not receiving thiram were pair-fed to the experimental ones. On d 30 of the experiment the animals were weighed and sacrificed, and the following organs were weighed: liver, kidneys, heart, epididymal and perirenal fat pads, testes, seminal vesicles, tibia, adrenals, and thyroid. Liver concentrations of lactate, pyruvate, beta-hydroxybutyrate, acetoacetate, ATP, and ADP were determined by enzymatic-spectrofluorimetric assay. For each parameter studied and each thiram dosage, values for treated rats were compared to those for control rats and the probability under the null hypothesis was computed. These probabilities were transformed into probits, logits, or "Weibull transforms" and plotted against the logarithms of the respective doses. Models were fitted to the data by linear regression techniques. Finally, the dose inducing the least significant difference (LSD dose), and the dose considered "safe" at P = 0.95, 0.99, and 0.999 were calculated. Significant pesticide-induced changes in the following parameters were found: food intake; weights of the whole body, kidneys, epididymal and perirenal fat pads, testes, and seminal vesicles; and liver beta-hydroxybutyrate/acetoacetate and lactate/pyruvate ratios. As the models did not differ in fit to the experimental data or in computed LSD doses, they were discriminated on the grounds of their underlying theoretical assumptions and their prediction of safe doses in a long-term study. The log-probit model was rejected for the former reason, and it was shown that the Weibull model foresees a nonnegligible risk of change, with thiram feeding at low doses, for too many parameters. The analysis resulted in the selection of the log-probit model for further use. Weight of fatty tissues was the most sensitive parameter and, using the log-probit model, the predicted no-effect dose at the 95 percent confidence level was 38 ppm thiram in the diet.

Animals↗

PubMed1995

Comparative effects of two dithiocarbamates disulfiram and thiram, on adrenal catecholamine content and on plasma dopamine-beta-hydroxylase activity.

Both disulfiram (tetraethylthiuram disulfide), an alcohol aversive drug, and thiram (tetramethyl-thiuram disulfide), a widely used pesticide, significantly increased the dopamine pool in the adrenal glands of dosed rats. The dopamine increase was detectable within 4 h of oral dosing with 100 mg/kg of either dithiocarbamate and peaked 24 h later at 10 times control values. In control rats the dopamine turnover was 0.51 h-1 as calculated by the assumed first order decline of dopamine after a single injection of alpha-methyl-p-tyrosine (alpha-MT, 400 mg/kg i.p.) resulting in a dopamine-beta-hydroxylase (DBH) activity of 0.73 nmol/h per pair of adrenals. In the adrenals of rats pretreated with thiram and then injected with alpha-MT, the adrenal dopamine content did not significantly decline, indicating that thiram reduced the conversion of dopamine to noradrenaline, eventually leading to the observed dopamine increase. Plasma DBH activity was significantly reduced 4 h and 24 h after dosing with thiram, but was unchanged after treatment with disulfiram. The determination of plasma DBH activity could be a marker to monitor the effect of thiram on catecholamine metabolism in occupationally exposed workers but not that of disulfiram in abstinent alcoholics.

Administration, Oral↗

PubMed2005

Effect of glutathione depletion on apoptosis induced by thiram in Chinese hamster fibroblasts.

Fungicide thiram, which is also known as an inducer of allergic contact dermatitis (ACD), was used as a model compound of thiuram chemicals, and its cellular effects were investigated in cultured Chinese hamster V79 cells. The level of intracellular reduced glutathione (GSH), protein sulfhydryl (PSH) groups, protein carbonyls (PC), membrane lipid peroxidation reflected by enhanced thiobarbituric acid reactive substrates (TBARS) production, as well as apoptotic effect were determined. The apoptosis induction was determined by assessing DNA fragmentation by TUNEL, annexin V binding, and caspases activation assays, using fluorescent microscope or flow cytometry, respectively. The concentrations of thiram required to induce cellular GSH depletion (by 40-50%), protein, and membrane lipid peroxidation (2-fold, and 1.7-fold, respectively), as well as to induce apoptosis in V79 Chinese hamster fibroblasts without causing necrosis through cytotoxic effects were between 50-100 microM. To investigate the role of decreased GSH content in the toxicity of thiram, GSH level was modified prior to exposure. Pretreatment of V79 cells with N-acetyl-L-cysteine (NAC), a GSH biosynthesis precursor, prevented GSH decrease, PC and TBARS production, as well as caspases activation induced by thiram exposure. On the other hand, thiram effects were enhanced by the previous depletion of cellular GSH by L-buthionine-(S,R)-sulfoximine (BSO).

Animals↗