Department of Pathology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2561
Received May 1, 2003; accepted August 15, 2003
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key Words: N,N-diethyldithiocarbamate; N-methyldithiocarbamate; pyrrolidine dithiocarbamate; disulfiram; carbon disulfide; neurotoxicity; hepatotoxicity; toluene-3,4-dithiol; 2-thiothiazolidine-4-carboxylic acid; 2-thiothiazolidin-4-ylcarbonylglycine.
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The reported biological effects and metabolites of dithiocarbamates and their disulfides are quite varied. At the cellular level, using in vitro models, dithiocarbamates have been shown to act as pro-oxidants or antioxidants, inhibitors or inducers of apoptosis, enzyme inhibitors, or modulators of transcription (Gessener and Gessner, 1992; Nobel et al., 1995
; Tsai et al., 1996
). Data acquired from humans and experimental animals have identified neurotoxicity and hepatotoxicity as sequelae to dithiocarbamate exposure (Forns et al., 1994
; Frisoni and Di Monda, 1989
; Rasul and Howell, 1973
). The nitrogen substituents and oxidation state of a dithiocarbamate influence its rate of decomposition, decomposition products, and metabolic pathways. Similarly, due to differences in acid stability and the potential for acid hydrolysis to occur following oral exposure, the route of exposure may also influence the disposition and biological effects of a dithiocarbamate in vivo. For example, oral administration of the acid labile N,N-diethyldithiocarbamate (DEDC) can produce biologically significant amounts of carbon disulfide (CS2) that manifest in CS2-mediated protein cross-linking (Johnson et al., 1998
). In contrast, parenteral administration of DEDC or oral administration of the more acid-stable dimer of DEDC, disulfiram, is characterized by the generation of S-(diethylaminocarbonyl)cysteine adducts in the absence of CS2-mediated protein cross-linking (Tonkin et al., 2000
, 2003
). Additionally, a single alkyl substituent on nitrogen bestows enhanced acid stability and provides for the generation of an alkyl isothiocyanate capable of acylating nucleophilic sites within biological systems (Thompson et al., 2002
). Consistent with the diversity of protein modifications observed for the individual dithiocarbamates has been the corresponding identification of separate toxicological targets and lesions. Oral administration of DEDC has been associated with the production of an axonopathy, whereas parental DEDC or po disulfiram produces a segmental demyelination. Relative to its dialkyl analog, N-methyldithiocarbamate has been demonstrated to be a more potent hepatotoxicant. Thus, characteristics such as acid stability and generation of an isothiocyanate appear biologically relevant and suggest that both the chemical structure and type of exposure must be taken into consideration when assessing hazards associated with exposure to a particular dithiocarbamate.
The potential for human exposure and toxicity to occur from dithiocarbamates supports a need for a method to evaluate internal exposure and better characterize the fate of dithiocarbamates within biological systems. Because CS2 is released in vivo by dithiocarbamates, biomarkers for CS2 including urinary 2-thiothiazolidine-4-carboxylic acid (TTCA), exhaled CS2, and dissolved CS2 in blood are potential dosimeters of dithiocarbamate exposure. A limitation of these three indices is that they only reflect free CS2 that has been released from a dithiocarbamate. Carbon disulfide is eliminated rapidly from biological systems and the quantity of CS2 released can vary considerably for equimolar doses of different dithiocarbamates, thereby hindering its utility as a common dosimeter. Alternative methods have used alkylation of the free dithiocarbamate in plasma followed by extraction and analysis by gas chromotography (GC) or gas chromotography mass spectrometry (GC/MS) (Cobby et al., 1978). Similarly, a method based upon high-performance liquid chromatography (HPLC) of parent dithiocarbamate has also been reported (Frank et al., 1995
). Methods measuring parent or alkylated dithiocarbamate have been useful for determining the pharmacokinetics of certain dithiocarbamates administered intravenously but are not well suited for evaluating occupational exposures and do not integrate cumulative exposures due to the relatively short half-lives of dithiocarbamates in plasma. A method for quantifying CS2-mediated protein modifications in blood based upon the reaction of thiol carbonyl moieties with toluene-3,4-dithiol (TdT) to generate toluene trithiocarbonate (TTC) has been demonstrated to exhibit a linear response following inhalation and ip exposure to CS2 (Valentine et al., 1999
). Because dithiocarbamates, dithiocarbamate disulfides, as well as CS2-mediated protein modifications are expected to produce TTC, this method may provide information that is complementary to existing methods for assessing exposures to dithiocarbamates. The biological life observed for TdT-reactive protein modifications also suggests that this assay may be able to integrate cumulative exposures.
To determine if TdT analysis can be used to detect and quantify internal exposure to dithiocarbamates, rats were exposed by oral or ip administration to representative dithiocarbamate compounds. Serial blood samples were then obtained and the plasma and hemolysate components analyzed for free and protein-associated TdT-reactive moieties. For comparison and to aid in evaluating the release of CS2 by the administered dithiocarbamates, the urinary CS2 metabolites TTCA and 2-thiothiazolidin-4-ylcarbonylglycine (TTCG) were also measured. The dithiocarbamates examined differed regarding their nitrogen substitution, oxidation state, and acid stability in order to assess the effect of these properties on the disposition of dithiocarbamates. The results obtained provide further insight into how the route of exposure and chemical structure of a dithiocarbamate may influence its toxicity. The results also support the utility of the TdT analysis as a complementary method to urinary CS2 metabolites for analyzing dithiocarbamates within biological systems.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Animals and exposures.
All exposures were conducted in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals. Male Sprague-Dawley rats, 250300 g, obtained from Harlan Bioproducts for Science (Indianapolis, IN) were used in this study. Prior to dosing, each animal was weighed and baseline blood samples from tail veins were obtained so that each animal could serve as its own control. The rats were given 1.5 mmol/kg body weight (bw) doses of CS2, DS, or the sodium salts of DEDC, NMDC, or PDTC (n = 4 per compound). The dithiocarbamate compounds were prepared in 0.1 M phosphate buffer, pH 7.5, and given at 24-h intervals for 5 days, either by oral gavage or intraperitoneal injection at a volume of 1 ml/100 g bw. Carbon disulfide was administered in corn oil such that 0.1 ml was given for each 100 g of bw. Because of low solubility, DS was administered as a suspension in 0.1 M phosphate buffer, pH 7.5 containing 1,2-propanediol:buffer (1:2, v:v) that was sonicated and passed through a 19-gauge needle to break up any large particles. This enabled the DS to be administered either through a 19-gauge needle or a gavage tube. Purity of the test compounds was determined spectrophotometrically to be approximately 99%. Freshly prepared solutions were diluted to 0.1 mM using 5 mM phosphate buffer, pH 7.4, the UV spectra of the diluted solutions were compared to published spectra, and the concentrations were determined using the appropriate extinction coefficients (Oktavec et al., 1979). The animals were dosed within one h of preparing the dosing solutions. For urine analysis, rats were housed individually in metabolic cages immediately after dosing and urine collected for 24 h. Control urine samples were collected at 24 h intervals for 12 days prior to dosing so that each animal would serve as its own control and urine samples were kept at -20°C until analysis. Blood samples from tail veins were obtained from anesthetized (100 mg/Kg bw of ketamine) animals 24 h after administration of the first and third doses, i.e., prior to administration of the second and fourth doses, respectively. Twenty-four h after administration of the fifth dose, deeply anesthetized animals were euthanized by aortic exsanguination.
Sample preparation for TTC analysis.
Heparinized blood samples were centrifuged at 4000 x g for 5 min. Plasma was removed and 50-µl aliquots were pipetted into 1.5-ml centrifuge tubes for TTC determination. A 10-µl aliquot of plasma was taken for protein determination. The red cells were resuspended in 5 mM phosphate buffer, pH 7.4 containing 150 mM NaCl, and were centrifuged again at 4000 x g for 5 min. The supernatant was withdrawn while carefully removing as much of the buffy coat as possible. This process was repeated two more times. The red cells were then lysed by adding 700 µl of 5 mM phosphate buffer, pH 7.4 for every 300 µl of red blood cells and centrifuged at 13,000 x g for 40 min. The resulting hemolysate was withdrawn and 100-µl aliquots were pipetted into 1.5-ml centrifuge tubes for TTC determination. A 20-µl aliquot of hemolysate was used for protein determination. To each of the 1.5-ml centrifuge tubes was added 100 µl water, 150 µl 0.2 M phosphate buffer (pH 8.5), 270 µl methanol, and 30 µl of 100 mM TdT in methanol. Samples were incubated for 1 h in a 65°C water bath with occasional mixing. Samples were allowed to cool to room temperature, at which time, ethyl acetate (200 µl) was added and mixed. Samples were then cooled overnight at -20°C, followed by centrifugation at 10,000 x g for 10 min.
HPLC analysis for TTC.
TTC was analyzed using a Perkin-Elmer Series A liquid chromatograph connected to a Shimadzu SPD-10A UV-VIS detector at 370 nm. Elution was done isocratically using an 80/20 mixture of methanol/water by volume on a Licrospher 100 RP-18 column (125 mm x 4 mm and 5-µm particles) at a flow rate of 1 ml/min. Retention time of TTC was 5.5 min under these conditions. Standard curves for TTC generated in plasma and hemolysate were obtained using freshly prepared N-acetyllysine dithiocarbamate that was reacted with TdT in the presence of plasma or hemolysate at 65°C for one h.
Determination of free and protein-bound TdT-reactive moieties.
Triplicate aliquots of plasma or hemolysate, obtained after the final dose of each compound, were centrifuged with an equal volume of hypotonic phosphate buffer through Amicon Microcon 10 microconcentrators per package directions. The filtrate and retentate were analyzed for TdT-reactive moieties, using HPLC as described above. The filtrates were analyzed for TTC to determine the concentration of parent compound or carbon disulfide, and the retentates were analyzed for TTC to determine the amount of protein associated TdT-reactive moieties in plasma and hemolysate. The results were determined as TTC in the filtrate or retentate as percent of total TTC in plasma or hemolysate before filtration.
Evaluation of TTC recoveries and acid stabilities.
To evaluate relative yields of TTC from dithiocarbamate-derived TdT-reactive moieties, standard solutions (100 µM) of N-acetyllysine dithiocarbamate and S-(methylaminothiocarbonyl) N-acetylcysteine were prepared separately in water. A 100-µM standard solution of CS2 was prepared in ethanol. Duplicate aliquots (50 µl) of each standard solution were added to separate 1.5-ml centrifuge tubes, to which was added 100 µl water, 150 µl 0.2 M phosphate buffer (pH 8.5), 270 µl methanol and 30 µl TdT (100 mM). The samples were incubated for 1 h in a 65°C water bath with occasional mixing. Samples were cooled overnight at -20°C, followed by centrifugation at 10,000 x g for 10 min, and TTC was analyzed by HPLC as described above.
The relative acid stabilities of the protein modifications N-acetyllysine dithiocarbamate and S-(methylaminothiocarbonyl) N-acetylcysteine were evaluated by adding 40 µl of 1N HCl to 4 ml aqueous solutions (100 µM) of each compound and incubated at room temperature. Following incubation periods of 1.5 h and 19 h, duplicate 1-ml aliquots of each sample were neutralized by adding 10 µl of 1 N NaOH. Aliquots (50 µl) of the neutralized solutions were added to 1.5-ml centrifuge tubes, derivatized with TdT, and TTC analyzed by HPLC as described above.
Urine TTCA and TTCG analysis.
Urine samples were centrifuged for 5 min. at 4000 x g and frozen at -20°C prior to TTCA and TTCG analysis. The solid-phase extraction steps prior to the chromatographic analysis were performed on multiple samples by passing urine through a Waters Oasis extraction cartridge (HLB 1cc) using a LiChrolut sample preparation unit with drying attachment (EM Science). A Waters 2690 LC with 996 diode array detector and Millennium software were used for the chromatographic analysis. Two columns (a Lichrosphere 100RP-8 10 µm 4 x 250 mm column connected to a Whatman Partisil 5 ODS-3 4.6 x 250 mm column) were used and the solvent systems were aqueous 2.53% acetonitrile with 1% acetic acid (A) and 95:4:1 methanol-water-acetic acid (B). The elution profile consisted of running 100% A isocratically for 18 min, 100% B for 6 min, and then 100% A again for 10 min before the next injection. To generate a standard curve for the estimation of TTCA and TTCG in rat urine samples, varying amounts of TTCA and TTCG were added to 0.5-ml aliquots of control rat urine containing a constant amount of T3CA. Peak area ratios of TTCA/T3CA and TTCG/T3CA were plotted against their mole ratios to measure TTCA and TTCG in nmoles/0.5 ml urine.
Determination of creatinine.
The determination of creatinine in the urine samples was performed using the Sigma Diagnostics creatinine kit 555-A (Sigma, St. Louis, MO). This kit uses a modified Jaffe reaction and was scaled down for use as a microplate assay on the SpectraMax 250 Plate Reader (Molecular Devices). A standard curve and 3-mg/dl creatinine standard were run with each sample plate. From the nmol of TTCA or TTCG in a 0.5-ml urine sample and the creatinine values, TTCA or TTCG was expressed as nmol per mg of creatinine in urine.
Protein determination of plasma and hemolysate.
The protein concentration of plasma was determined using the Bio-Rad Protein Assay, with bovine serum albumin (BSA) for the standard curve. Hemolysate concentrations were measured by taking the absorbance at 540 nm (max of heme) and using the equation Absorbance540 x 1.14 x dilution = mg/ml protein where 1.14 is a constant. Normally 57 mg of protein was present in the 100 µl of hemolysate used for derivatization with TdT.
Statistical analyses.
Descriptive statistics, F-tests, and Students t-test were performed for both unequal and equal variances, using Microsoft Excel software. ANOVA, inclusive of Dunnetts multiple comparison test for measuring differences between control and treatment groups and Bonferronis multiple comparison test (Kapinski, 1991) to measure differences between the CS2 treatment group and dithiocarbamate-treated group, were performed using GraphPad Prism software. The level of significance was taken to be p < 0.05, unless otherwise noted.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Levels of TTC in Plasma from Repeated Dosing
TTC was detected in plasma as a single peak eluting between 5 to 6 min (Fig. 1). Levels of TdT-reactive species in plasma, following administration of CS2, DS, and DEDC, appeared to increase over the period of ip administration (Fig. 2A
). In contrast, no TdT-reactive moieties were observed following ip administration of NMDC or PDTC. TTC could be generated from the plasma obtained following po administration of all compounds tested (Fig. 2B
). Significant increases in TTC levels from day 1 to day 5 were observed for all the compounds administered orally and for CS2 and DEDC administered ip, consistent with accumulation of TdT-reactive moieties over the exposure period. This trend was also observed for DS administration ip, which showed a significant increase in TTC levels from day 1 to day 3.
|
|
|
|
Dependence of Urinary TTCA and TTCG on Route of Exposure
The amounts of TTCA and TTCG, excreted in the urine over a 24-h period following a single dose of each test compound, are presented in Figure 4. Significantly greater amounts of TTCA were excreted following oral exposure, relative to ip administration, for each compound. The relative amounts of TTCA excreted in the urine for each of the dithiocarbamates, following oral administration, increased in the order DEDC
DS < NMDC < PDTC; and following ip administration, urinary TTCA increased in the order PDTC < NMDC < DS < DEDC. Smaller quantities of TTCG were excreted relative to TTCA, but a similar relationship was observed regarding the relative amounts of TTCG excreted following oral vs. ip administration. Also, similar to TTCA, significantly greater amounts of TTCG excretion resulted from oral exposure relative to ip administration, with the exception of CS2 and DEDC for which there was no difference between oral and ip routes of exposure.
|
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Production of TTC from the retentate of plasma and hemolysate is consistent with the generation of protein-associated TdT-reactive moieties. As mentioned previously, CS2-derived protein dithiocarbamates are expected to be the predominant protein associated, TdT-reactive moiety and the data appears consistent with this interpretation. Based on the pKas of the test compounds (Fig. 7), oral administration is expected to favor acid-promoted decomposition with generation of CS2. Accordingly, oral administration resulted in detectable levels of protein-associated dithiocarbamates for all the compounds. In contrast to the results obtained for oral administration, not all compounds produced protein-associated TdT-reactive moieties after ip administration. Intraperitoneal administration of either NMDC or PDTC did not result in TdT-reactive protein modifications in plasma, and PDTC produced no TdT-reactive moieties on hemolysate proteins as well. These observations are consistent with minimal mixed disulfide formation or decomposition of NMDC and PDTC occurring when exposure to either of these compounds occurs parenterally. Indeed, both NMDC and PDTC are less susceptible to acid-promoted decomposition relative to straight-chain dialkyl dithiocarbamates; and this has been the basis for using PDTC in in vitro biological systems when activities mediated by parent dithiocarbamate are desired (Nobel et al., 1995
). The much greater stability of PDTC relative to straight-chain dialkyldithiocarbamates, and therefore decreased generation of CS2 at neutral pH, may account for the inability to detect TdT-reactive species following ip administration of PDTC (Thompson et al., 2002
; Tonkin et al., 2003
). Interestingly though, ip administration of NMDC produced the greatest level of reactive protein modifications in hemolysate, suggesting either intracellular decomposition to amine and CS2 or, more likely, that decomposition or metabolism to methylisothiocyanate occurred accompanied by dithiocarbamate ester formation, as has been observed for hepatic glutathione (Lam et al., 1993
; Thompson et al., 2002
). Relative to the other compounds in this study, NMDC is more base-labile and has been shown to undergo facile generation of isothiocyanate at physiological pH, resulting in covalent modification of nucleophilic sites of proteins (Valentine et al., 1995
). Although methylisothiocyanate can also react with protein amino functions to produce methylthiourea protein adducts, this covalent modification would not have been detected by the TdT analysis. The data suggest that entrance of NMDC into the red cell favors generation of methylisothiocyanate that is trapped as dithiocarbamate ester, due to the high concentration of globin sulfhydryl functions within the red cell (Rossi et al., 1998
).
|
TTCA is an established urinary metabolite of CS2 and is currently used to monitor exposure in the workplace. Generation of TTCA is thought to proceed through the addition of CS2 to glutathione to generate a trithiocarbonate, followed by removal of glutamic acid and glycine in the mercapturic acid metabolic pathway (Fig. 8) (Bus, 1985
). Support for this metabolic pathway has been provided by the identification of TTCG, the cyclic metabolite formed prior to removal of glycine (Amarnath et al., 2001
). Although TTCA may also be produced from the addition of CS2 to either cysteinyl glycine or cysteine, the lower concentrations of these two sulfhydryl donors in biological systems suggests their contribution will be considerably less than that of glutathione. In any of these possibilities though, the release of CS2 from parent dithiocarbamate is thought to be required for production of TTCA or TTCG, and thus, these two metabolites are expected to reflect the bioavailability of CS2 from each compound and route of exposure.
|
Examining urinary TTCA in conjunction with TdT-reactive moieties in plasma and hemolysate demonstrates that the bioavailability of CS2 and distribution of parent dithiocarbamate varies depending on the route of exposure and structure of the dithiocarbamate. The greatest levels of CS2-mediated protein modification resulted from oral exposures consistent with the report that oral administration of DEDC can produce a CS2-mediated distal axonopathy accompanied by covalent protein cross-linking (Erve et al., 1998; Johnson et al., 1998
). Examination of the plasma filtrates demonstrated the greatest amounts of free parent dithiocarbamate for disulfiram following oral exposure. It is, therefore, of interest to note that although disulfiram is the dimer of DEDC, when disulfiram is administered orally, it produces a Schwannopathy, as does DEDC administered parenterally, suggesting that dithiocarbamate disulfides can be absorbed intact and then be reduced, serving as a source of systemic free dithiocarbamate after oral exposure (Tonkin et al., 2000
). The monoalkyl dithiocarbamate examined demonstrated the ability to produce high levels of intracellular protein modifications in the absence of similar extracellular protein modifications. Thus, the ability of NMDC to generate an isothiocyanate metabolite appears biologically relevant and this property may be responsible for the greater hepatotoxicity of NMDC relative to its dialkyl analog following oral exposure (Thompson et al., 2002
).
Conclusion
Several limitations and strengths of the two analytical methods are apparent from this investigation. Analysis of urinary TTCA demonstrated greater sensitivity through its ability to detect PDTC exposure following ip administration that, in comparison, produced undetectable levels of TdT-reactive moieties in blood; but, the amount of TTCA excreted in the urine appears to be dependent upon more than just the level of internal CS2 exposure, as demonstrated by the greater levels of TTCA generated from oral administration of dithiocarbamates relative to equimolar doses of CS2. Although the ability of TdT analysis to detect multiple chemical species makes interpretation of the results more complex, this characteristic also provides greater versatility and is more amenable to the detection of all dithiocarbamates within biological systems. Since TdT analysis can detect parent dithiocarbamates, it can potentially also be used to detect dithiocarbamates and their disulfides in other biological and non-biological matrices. To its advantage the analysis of proteins by TdT also appears to reflect cumulative exposures, allows for a longer time period for procuring samples after cessation of exposure, and detects non-CS2-mediated protein modifications produced by dithiocarbamates as compared to urinary TTCA or previous methods used to analyze dithiocarbamates in plasma. Together the two analytical methods, TdT analysis and TTCA excretion, provide complimentary information that has provided further insight into the relative bioavailability of CS2 and parent compound resulting from oral and non-oral exposure to NMDC, DEDC, PDTC and DS that helps to interpret the differences in toxicity observed for these structurally related compounds. The data from this study are also useful for extrapolating data derived from in vitro studies on dithiocarbamates to in vivo systems.
![]() |
ACKNOWLEDGMENTS |
---|
![]() |
NOTES |
---|
2 To whom correspondence should be addressed at the Department of Pathology, Room C3320 Medical Center North, Vanderbilt University Medical Center, Nashville, TN 37232-2561. Fax: (615) 343-9825. E-mail: bill.valentine{at}mcmail.vanderbilt.edu.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Aspila, K. L., Chakrabarti, C. L., and Sastri, V. S. (1973). Substituent effects on acid dissociation constants of N,N-substituted dithiocarbamic acids. Anal. Chem. 45, 363367.[ISI]
Awni, W. M., Hoff, J. V., Shapiro, B. E., and Halstenson, C. E. (1994). A dose-ranging pharmacokinetics study of sodium diethyldithiocarbamate in normal healthy volunteers. J. Clin. Pharmacol. 34, 11831190.
Bach, S. P., Chinery, R., ODwyer, S. T., Potten, C. S., Coffey, R. J., and Watson, A. J. (2000). Pyrrolidine dithiocarbamate increases the therapeutic index of 5-fluorouracil in a mouse model. Gastroenterology 118, 8189.[ISI][Medline]
Brewer, C. (1993). Recent developments in disulfiram treatment. Alcohol Alcohol. 28, 383395.[Abstract]
Bus, J. S. (1985). The relationship of carbon disulfide metabolism to development of toxicity. Neurotoxicology 6, 7380.[ISI][Medline]
Chinery, R., Brockman, J. A., Peeler, M. O., Shyr, Y., Beauchamp, R. D., and Coffey, R. J. (1997). Antioxidants enhance the cytotoxicity of chemotherapeutic agents in colorectal cancer: A 53-independent induction of p21WAF1/CIP1 via C/EBPß. Nat. Med. 3, 12331241.[ISI][Medline]
Cobby, J., Mayerson, M., and Selliah, S. (1978). Disposition kinetics in dogs of diethyldithiocarbamate, a metabolite of disulfiram. J. Pharmacokinet. Biopharm. 6, 369387.[ISI][Medline]
DeWoskin, R. S., and Riviere, J. E. (1991). Cisplatin-induced loss of kidney copper and nephrotoxicity is ameliorated by single-dose diethyldithiocarbamate but not mesna. Toxicol. Appl. Pharmacol. 112, 182189.[ISI]
Eneanya, D. I., Bianchine, J. R., Duran, D. O., and Andresen, B. D. (1981). The actions and metabolic fate of disulfiram. Ann. Rev. Pharmacol. Toxicol. 21, 575596.[CrossRef][ISI][Medline]
Erve, J. C. L., Amarnath, V., Sills, R. C., Morgan, D. L., and Valentine, W. M. (1998). Characterization of a valine-lysine thiourea cross-link on rat globin produced by carbon disulfide or N,N-diethyldithiocarbamate in vivo. Chem. Res. Toxicol. 11, 11281136.[CrossRef][ISI][Medline]
Forns, X., Caballeria, J., Bruguera, M., Salmeron, J. M., Vilella, A., Mas, A., Pares, A., and Rodes, J. (1994). Disulfiram-induced hepatitis. Report of four cases and review of the literature. J. Hepatol. 21, 853857.[ISI][Medline]
Frank, N., Christmann, A., and Frei, E. (1995). Comparative studies on the pharmacokinetics of hydrophilic prolinedithiocarbamate, sarcosinedithiocarbamate and the less hydrophilic diethyldithiocarbamate. Toxicology 95, 113122.[CrossRef][ISI][Medline]
Frisoni, G. B., and Di Monda, V. (1989). Disulfiram neuropathy: A review (19711988) and report of a case. Alcohol Alcohol. 24, 429437.[ISI][Medline]
Gessener, P. K. and Gessner, T. (1992). Disulfiram and Its Metabolite Diethyldithiocarbamate Pharmacology and Status in the Treatment of Alcoholism, HIV Infections, AIDS, and Heavy Metal Toxicity. Chapman & Hill, New York.
Haley, T. J. (1979). Disulfiram (tetraethylthioperoxydicarbonic diamide): A reappraisal of its toxicity and therapeutic application. Drug Metab. Rev. 9, 319335.[ISI][Medline]
Johnson, D. J., Graham, D. G., Amarnath, V., Amarnath, K., and Valentine, W. M. (1996). The measurement of 2-thiothiazolidine-4-carboxylic acid as an index of the in vivo release of CS2 by dithiocarbamates. Chem. Res. Toxicol. 9, 910916.[CrossRef][ISI][Medline]
Johnson, D. J., Graham, D. G., Amarnath, V., Amarnath, K., and Valentine, W. M. (1998). Release of carbon disulfide is a contributing mechanism in the axonopathy produced by N,N-diethyldithiocarbamate. Toxicol. Appl. Pharmacol. 148, 288296.[CrossRef][ISI][Medline]
Jones, S. G., and Jones, M. M. (1984). Structure-activity relationships among dithiocarbamate antidotes for acute cadmium chloride intoxication. Environ. Health Perspect. 54, 285290.[ISI][Medline]
Kapinski, K. F. (1991). Statistical analysis of behavioral data. In Statistics in Toxicology (D. Krewski and C. Franklin, Eds.), pp. 421. Gordon & Breach, New York.
Kopecky, J., and Smejkal, J. (1984). A simple preparation of pure 2-thiothiazolidine-4-carboxylic acid (TTCA) as a reference standard for carbon disulfide exposure tests. Bull. Soc. Chim. Belg. 93, 231232.[ISI]
Lam, W. W., Kim, J. H., Sparks, S. E., Quistad, G. B., and Casida, J. E. (1993). Metabolism in rats and mice of the soil fumigants metham, methyl isothiocyanate, and dazomet. J. Agric. Food Chem. 41, 14971502.[ISI]
Nobel, C., Kinland, M., Lind, B., Orrenius, S., and Slater, A. (1995). Dithiocarbamates induce apoptosis in thymocytes by raising the intracellular level of redox-active copper. J. Biol. Chem. 270, 2620226208.
Oktavec, D., Stefanec, J., Siles, B., Konecny, V., and Garaj, J. (1979). Electronic spectra of salts of dithiocarbamic acids. Collec. Czech. Chem. Comm. 44, 24872493.[ISI]
Rasul, A. R., and Howell, J. M. (1973). Further observations on the response of the peripheral and central nervous system of the rabbit to sodium diethyldithiocarbamate. Acta Neuropathol. 24, 161173.[ISI][Medline]
Rossi, R., Barra, D., Bellelli, A., Boumis, G., Canofeni, S., Simplicio, P. D., Lisini, L., Pascarella, S., and Amiconi, G. (1998). Fast-reacting thiols in rat hemoglobins can intercept damaging species in erythrocytes more efficiently than glutathione. J. Biol. Chem. 273, 1919819206.
Thompson, R. W., Valentine, H. L., and Valentine, W. M. (2002). In vivo and in vitro hepatotoxicity and glutathione interactions of N-methyldithiocarbamate and N,N-dimethyldithiocarbamate in the rat. Toxicol. Sci. 70, 269280.
Tonkin, E. G., Erve, J. C. L., and Valentine, W. M. (2000). Disulfiram produces a noncarbon disulfide-dependent Schwannopathy in the rat. J. Neuropathol. Exp. Neurol. 59, 786797.[ISI][Medline]
Tonkin, E. G., Valentine, H. L., Zimmerman, L. J., and Valentine, W. M. (2003). Parenteral N,N-diethyldithiocarbamate produces segmental demyelination in the rat that is not dependent on cysteine carbamaylation. Toxicol. Appl. Pharmacol. 189, 139150.[CrossRef][ISI][Medline]
Tsai, J., Jain, M., Hsieh, C., Lee, W., Yoshizumi, M., Patterson, C., Perrella, M., Cooke, C., Wang, H., Haber, E., et al. (1996). Induction of apoptosis by pyrrolidine dithiocarbamate and N-acetylcysteine in vascular smooth muscle cells. J. Biol. Chem. 271, 36673670.
Valentine, W. M., Amarnath, V., Amarnath, K., and Graham, D. G. (1995). Characterization of protein adducts produced by N-methyldithiocarbamate and N-methyldithiocarbamate esters. Chem. Res. Toxicol. 8, 254260.[ISI][Medline]
Valentine, W. M., Valentine, H. L., Amarnath, K., and Amarnath, V. (1999). Toluene-3,4-dithiol analysis of blood for assessing carbon disulfide exposure. Toxicol. Sci. 50, 155163.[Abstract]
Vettorazzi, G., Almeida, W., Burin, G., Jaeger, R., Puga, F., Rahde, A., Reyes, F., and Schvartsman, S. (1995). International Safety Assessment of Pesticides: Dithiocarbamate Pesticides, ETU, and PTU-A Review and Update. Teratog. Carcinog. Mutagen. 15, 313337.[CrossRef][ISI][Medline]
World Health Organization (WHO) (1988). Dithiocarbamate Pesticides, Ethylenethiourea, and Propylenethiourea: A General Introduction. World Health Organization, Geneva.
Zhang, Y., Cho, C., Posner, G., and Talalay, P. (1992). Spectroscopic quantitation of organic isothiocyanates by cyclocondensation with vicinal dithiols. Anal. Biochem. 205, 100107.[ISI][Medline]
Zhang, Y., Wade, K., Prestera, T., and Talalay, P. (1996). Quantitative determination of isothiocyanates, dithiocarbamates, carbon disulfide, and related thiocarbonyl compounds by cyclocondensation with 1,2-benzenedithiol. Anal. Biochem. 239, 160167.[CrossRef][ISI][Medline]
|