Identification of a new urinary metabolite of carbon disulfide using an improved method for the determination of 2-thioxothiazolidine-4-carboxylic acid

A new method is reported for the analysis of 2-thioxothiazolidine-4-carboxylic acid (TTCA) in urine that is amenable to automation and provides greatly simplified chromatograms. The method comprises the addition of tetrahydro-2-thioxo-2H-1,3-thiazine-4-carboxylic acid, which is chemically similar to TTCA, as internal standard, purification on an Oasis HLB solid-phase extraction column, and analysis by HPLC with UV detection. The limit of detection for TTCA was 40 pmol/mL of urine, recovery was 79.3 +/- 1.0%, and detection was linear over at least 3 orders of magnitude. In addition, during the analysis of urine samples from workers exposed to CS(2), a novel urinary metabolite of CS(2) was recognized. The new metabolite demonstrated a dose response, was present at approximately 30% the level of TTCA, and was charaterized to be 2-thioxothiazolidin-4-ylcarbonylglycine (TTCG). Administration of TTCG to rats resulted in excretion of TTCA suggesting that TTCG is a likely precursor of TTCA. Although urinary excretion of both TTCA and TTCG resulted from administration of captan, only TTCA was detected following administration of methyl isothiocyanate. The greater selectivity of TTCG suggests that co-analysis of TTCA and TTCG in urine may aid in differentiating exposures to CS(2), captan and isothiocyanates.     

Alcohol and urinary 2-thiothiazolidine-4-carboxylic acid

The aim of this work was to study the effect of alcohol on the excretion characteristics of urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) in people exposed to carbon disulfide (CS(2)) and in non-exposed subjects. Ten male non-exposed volunteers consumed 150, or 250 ml, of liquor (38 degrees ) and the excretion dynamics of urinary TTCA were detected by HPLC. A questionnaire and urinary TTCA analyses were conducted in 152 male workers exposed to CS(2) and 60 male controls. CS(2) concentrations at the workplace were measured by GC. Results showed that urinary TTCA levels in non-exposed volunteers reached a high peak 3 h after drinking 150 ml liquor, which returned 12 h later to the levels before drinking; TTCA levels were in accordance with the quantity of alcohol consumed. There were increasing tendency of urine TTCA levels in workers exposed to different concentrations of CS(2) (10 ppm). TTCA levels in people with drinking habits seemed higher in the non-exposed group than in the exposed group, especially in those exposed over 10 ppm. The results suggest that the consumption of liquor in large quantities may interfere with the levels of urinary TTCA. Thus, in biomonitoring of CS(2) a suitable sampling time is important to avoid a biased estimation of CS(2) exposure.     

The influence of simultaneous exposure to carbon disulfide and hydrogen sulfide on the peripheral nerve toxicity and metabolism of carbon disulfide in rats

Three groups of 10 male Sprague-Dawley rats were exposed daily, 5 days a week for 25 weeks, either to 500 ppm carbon disulfide (CS2), 50 ppm hydrogen sulfide (H2S), or to both of them as a mixture and were periodically examined for sensory and motor tail nerve conduction velocity (SNCV, MNCV). A concomitant control group of 10 rats was used. In addition, rats exposed to 500 ppm CS2, and those simultaneously exposed to 500 ppm CS2 and 50 ppm H2S, were twice examined for 24-h urine excretion of 2-thio-thiazolidine-4-carboxylic acid (TTCA) in the course of the experimental period. Simultaneous exposure to CS2 and H2S had no significant interactive effect on nerve conduction velocities. A significant time-dependent slowing down of MNCV and SNCV occurred as the result of chronic exposure to CS2, including exposure to 500 ppm CS2 and to the mixture of 500 ppm CS2 and 50 ppm H2S, but did not occur after chronic exposure to 50 ppm H2S. With combined exposure to 500 ppm CS2 and 50 ppm H2S, the quantity of TTCA excreted in 24-h urine was not significantly different from that occurring in response to CS2 exposure alone. On the basis of these results it is suggested that chronic exposure to H2S would neither influence CS2-induced peripheral nerve toxicity nor obscure the interpretation of the measurement of urinary TTCA as a biological indicator of CS2 exposure.     

Covalent cross-linking of proteins by carbon disulfide.

Carbon disulfide is known to react with amino groups of proteins to generate dithiocarbamates (2). We observed covalent cross-linking of dithiocarbamate-derivatized proteins under physiological conditions which may occur through several mechanisms. Evidence for the structure of these covalent bridges and the reactive intermediate was obtained using 13C NMR spectroscopy in conjunction with specific isotopic labeling. On incubation at 37 degrees C oxidative coupling of dithiocarbamates generated bis(thiocarbamoyl) disulfides (3) which were reduced by cysteine. In addition, an electrophilic isothiocyanate (4) was generated from decomposition of the dithiocarbamate. Nucleophilic addition of sulfhydryl and amine moieties to the isothiocyanate produced dithiocarbamate ester (5) and thiourea linkages (6), respectively. Evidence for the presence of inter- and intramolecular cross-links was obtained using denaturing polyacrylamide gel electrophoresis under reducing conditions. The formation of isothiocyanate in neutral solution, through elimination of sulfhydryl ion, was correlated with increased pKa values of the parent amine of amino acids. Dithiocarbamates derived from terminal amino groups of proteins did not appear to generate isothiocyanate or form thiourea or dithiocarbamate ester. Both the thiourea and the dithiocarbamate ester were stable at reduced pH, whereas in alkaline media the thiourea was stable but dithiocarbamate ester was hydrolyzed. Although the disulfide and ester linkages were formed more rapidly than the thiourea, generation of the latter appeared to be irreversible, leading to its gradual accumulation over a longer period of time. Generation of isothiocyanate by CS2-derived dithiocarbamates and subsequent covalent cross-linking of proteins may provide a molecular mechanism for CS2-induced axonopathy.     

Effects of the dithiocarbamate fungicide propineb in primary neuronal cell cultures and skeletal muscle cells of the rat

After repeated-dose toxicity studies with the fungicide propineb, reversible effects on muscle functions were found. Therefore, mechanistic investigations should contribute to clarification of its mode of action in relation to disulfiram and diethyldithiocarbamate neurotoxicity or direct effects on muscle cells. In principle, besides the dithiocarbamate effects, two different mechanisms have been discussed for this fungicide. One mechanism is the degradation to carbon disulfide (CS(2)) and propylenthiourea (PTU) and the other are direct effects of zinc. Primary neuronal cell cultures of the rat are a well established model to identify neurotoxic compounds like n-hexane or acrylamide. In this cell culture model, endpoints such as viability, energy supply, glucose consumption and cytoskeleton elements were determined. Additionally, skeletal muscle cells were used for comparison. Propineb and its metabolite PTU were investigated in comparison to CS(2), disulfiram and diethyldithiocarbamate. The toxicity of zinc was tested using zinc chloride (ZnCl(2)). It was clearly shown that propineb exerted strong effects on the cytoskeleton of neuronal and non-neuronal cell cultures (astrocytes, muscle cells). This was similar to ZnCl(2,) but not to CS(2). With CS(2) and disulfiram effects on the energy supply were more prominent. In conclusion, the toxicity of propineb is not comparable to disulfiram, diethyldithiocarbamate or CS(2) neurotoxicity. In regard to these findings, a direct reversible effect of propineb on skeletal muscle cells seems to be more likely.     

Effects of dithiocarbamates on cadmium distribution and excretion in chronically exposed rats

One month after termination of a 3-mo exposure of rats to cadmium (Cd in drinking water at a concentration of 50 mg/l), the effects of dithiocarbamate analogs on the excretion and distribution of the cadmium were determined. Sodium salts of three dithiocarbamates [sodium bis(hydroxyethyl) dithiocarbamate, DEDTC; sodium N-methyl-D-glucamine dithiocarbamate, MGDTC; and sodium 4-carboxamidopiperidine dithiocarbamate, INADTC] were given to rats ip 2 times at 2.46 mmol/kg. In the following administration of the first injection of DEDTC, cadmium excretion via the urine amounted to 15.8 micrograms and via bile amounted to 124.4 micrograms Cd. Following administration of MGDTC, the urinary and biliary excretions of cadmium were 14.5 and 47 micrograms, respectively, while in the case of INADTC the corresponding values were 23.6 and 7.9 micrograms cadmium. In control animals the urinary and biliary excretion per 12 h reached 0.09 and 0.12 micrograms Cd. Gel permeation chromatography (GPC) analysis of bile revealed differences in the distribution of Cd in the elution fractions after the first injections of the individual dithiocarbamates. For all three dithiocarbamates, significant decreases of the concentrations of cadmium in the liver and kidney were found. DEDTC (but neither of the other compounds) increased the concentration of cadmium in the brain from control levels of 49 +/- 5 ppb to 105 +/- 16 ppb.     

Excretion of ttca in human umne after administration of disulfiram

2-Thiothiazolidine-4-carboxylic acid (TTCA) was measured in urine of two persons given an oral dose of 250 mg disulfiram. Maximum concentrations up to 0.33 mmol $\text{TTCA}\text{mol}$ creatinine were found, 10 to 14 h after dosing. The total amounts of TTCA excreted in urine were 1.8 and 3.5 μmol, respectively, which correspond to 0.2 and 0.41% of the dose.     

Parenteral N,N-diethyldithiocarbamate produces segmental demyelination in the rat that is not dependent on cysteine carbamylation

Disulfiram, a dithiocarbamate drug used in alcohol aversion therapy, produces a peripheral neuropathy characterized in rats as segmental demyelination accompanied by generation of S-(diethylaminocarbonyl)cysteine (DETC-Cys) adducts. N,N-Diethyldithiocarbamate (DEDC) is a major metabolite of disulfiram that can undergo methylation and oxidation to S-methyl-N,N-diethylthiocarbamate (MeDETC) sulfoxide and sulfone, thought to be responsible for carbamylation of sulfhydryl functions by disulfiram. To assess the role of cysteine carbamylation in disulfiram toxicity, DEDC and MeDETC were administered parenterally to male Sprague-Dawley rats for 4 and 8 weeks. The roles of the disulfide linkage in disulfiram and of carbamylated glutathione metabolites were assessed by administering S-(diethylaminodithiocarbonyl)N-acetylcysteine (DS-NAC) and S-(diethylaminocarbonyl)-N-acetylcysteine (DETC-NAC), respectively, parenterally for 12 weeks. Following exposure, spinal cord-derived neurofilament preparations and hemoglobin were isolated and analyzed by RP-HPLC and LC/MS/MS for the presence of DETC-Cys adducts. Peripheral nerve sections were also obtained and examined by light and electron microscopy for morphological lesions. RP-HPLC analysis of globin preparations from DEDC-, MeDETC-, and DS-NAC-exposed animals demonstrated a late-eluting peak, identical to that reported for disulfiram-generated DETC-Cys adducts on the beta(3)-globin chain. DETC-NAC exposure did not result in detectable globin modification by RP-HPLC. The quantity of DETC-Cys adducts produced on globin and neurofilament preparations determined by LC/MS/MS was twofold greater for MeDETC than DEDC following equimolar doses of each compound. Primary myelin lesions consisting of demyelinated axons and myelin splitting were observed in peripheral nerves following exposure to DEDC for 8 weeks. No lesions were detected following exposure to MeDETC, DS-NAC, or DETC-NAC at any time point or dose level. These results are consistent with DEDC, but not the other metabolites, being a demyelinating agent and thus a potential proximate toxic species for disulfiram-mediated demyelination. The production of significantly greater levels of DETC-Cys adducts by MeDETC relative to DEDC in the absence of neurotoxicity for MeDETC is consistent with cysteine carbamylation not contributing to the demyelination produced by disulfiram and DEDC.     

Assessment of intramuscular emulsified disulfiram in alcoholics by estimation of urinary diethylamine

Five alcoholics administered 1 g of disulfiram in soybean emulsion by deep intramuscular injection were found to have insignificant urinary levels of disulfiram metabolites compared with five patients on oral disulfiram. Disulfiram administered in this way is unlikely to produce a significant reaction with ethanol, but its value as a placebo should not be discounted. In this pilot trial, the technique caused moderate local and systemic reactions and possible hepatic toxicity. Although in other respects the method is superior to surgical implants, modification of dosage and vehicle will be necessary, and the high incidence and severity of side effects preclude further clinical use of disulfiram in this form. Based on the work of Gordis and Peterson, a qualitative and quantitative thin-layer chromatographic urine assay method for the disulfiram metabolite diethylamine, measured as cupric diethyldithiocarbamate, was developed. This is practicable in a hospital laboratory situation and has application for compliance testing in patients on oral disulfiram.     

Dietary copper enhances the peripheral myelinopathy produced by oral pyrrolidine dithiocarbamate.

The neurotoxic hazard of a dithiocarbamate is influenced by route of exposure and acid stability of the dithiocarbamate. As an example, oral administration of the acid labile dithiocarbamate N,N-diethyldithiocarbamate (DEDC) causes a central-peripheral axonopathy thought to result from acid-promoted decomposition to CS2 in the stomach. In contrast, parenteral administration of DEDC, which bypasses the acidic environment of the stomach, causes a primary demyelination that is thought to be mediated through the intact parent dithiocarbamate. The relative acid stability of pyrrolidine dithiocarbamate (PDTC) suggests that a significant portion of a dose can be absorbed intact following oral exposure with the potential to produce a primary myelin injury. The present study was performed to characterize the neurotoxicity of PDTC and evaluate the possible role of copper in dithiocarbamate-mediated demyelination. Male Sprague Dawley rats were administered PDTC in drinking water and given either a normal- or high-copper diet for 18, 47, or 58 weeks. Examination of peripheral nerve by light microscopy and electron microscopy at the end of exposures revealed primary myelin lesions and axonal degeneration in the PDTC groups, with a significant increase in the severity of several lesions observed for the PDTC, high-copper group relative to the PDTC normal-copper diet. ICP-AES metal analysis determined that the PDTC groups had significantly increased brain copper, and at 58 weeks a significant increase in copper was seen in the sciatic nerve of PDTC high-copper animals relative to PDTC normal-copper diet animals. Although RP-HPLC analysis could not detect globin alkylaminocarbonyl cysteine modifications analogous to those seen with parenteral DEDC, LC/MS/MS identified (pyrrolidin-1-yl carbonyl)cysteine adducts on PDTC-exposed rat globin. These findings are consistent with previous studies supporting the ability of acid-stable dithiocarbamates to mediate myelin injury following oral exposure. The greater severity of lesions associated with dietary copper supplementation and elevated copper levels in nerve also suggests that perturbation of copper homeostasis may contribute to the development of myelin lesions.     

Formation of methylthio metabolites of indene in the guinea pig and the rat

The formation of methylthio metabolites of epoxides has been shown to be a significant route of metabolism in some species. Several aspects of this metabolic conversion for indene were examined. Two isomers of hydroxy(methylthio)indane were found in the urine of guinea pigs administered indene (14.3 and 100 mg/kg, ip). The major isomer, 2-hydroxy-1-methylthioindane (I) was present as 6-9% of the administered dose after 24 hr, while lower amounts (0-0.6%) of a minor isomer (II) were observed. A significant amount of isomer I was found as a urinary metabolite of indene oxide (14% of 12.5 mg/kg, ip). To further elucidate the route of formation of I, the glutathione (I-GLU) and mercapturic acid (I-MER) conjugates of indene oxide were synthesized and administered to the guinea pig. The methylthio metabolite I was present as a significant urinary metabolite of both conjugates of indene oxide, comprising 9.6% and 5.7% of the dose of I-GLU (5 mg, ip) and I-MER (4 mg, ip), respectively. These results show that the formation of a hydroxy(methylthio)indane is a significant route of metabolism for indene and indene oxide in the guinea pig, and that this metabolite arises via further metabolism of conjugates in the glutathione pathway. In the rat, isomer I is a minor metabolite. Mechanistic aspects of the formation of these thioether metabolites are discussed.     

Identification and determination of 2-thiothiazolidine-4-carboxylic acid in urine of workers exposed to carbon disulfide

A compound was isolated from the urine of workers exposed to carbon disulfide during the production of rayon. The compound was identified as 2-thiothiazolidine-4-carboxylic acid (TTCA) by GC/MS and NMR. A HPLC method for the quantitative determination of TTCA was elaborated and applied to urine samples. The method allowed detection of TTCA concentrations in urine as low as 5 × 10^–7 M.No TTCA was detected in urine of workers occupationally exposed to organic solvents other than CS₂. High concentrations of TTCA (upto 32×10^–5 M) were shown to be present in urine of spinners exposed to CS₂ concentrations of approximately 100 mg/m³. It is suggested that the assay of urinary TTCA is suitable for detection of occupational exposure to CS₂.     

Placental transfer and fetal distribution of cadmium and mercury after treatment with dithiocarbamates

The distribution in pregnant C57BL mice (day 18 of gestation) of intravenously administered cadmium (Cd) chloride and mercury (Hg) chloride (0.75 mol/kg b.w.) was studied, with or without previous dithiocarbamate pretreatment. Diethyldithiocarbamate (DEDTC), disulfiram, or thiram (2×1 mmol/kg b.w.) or vehicle (gelatine) alone, were given by gavage 2 h before and immediately after injection of the metals. The mice were sacrificed 4 and 24 h later and subjected to autoradiography or impulse counting of excised organs.All the dithiocarbamates increased the concentration of both Cd and Hg in brain and most other maternal organs. While DEDTC and thiram, in that order, strongly increased Cd concentrations in whole fetuses (around 17-fold at 4 h) and all fetal organs measured, disulfiram caused a decrease in fetal Cd concentrations. For Hg, all the dithiocarbamates substantially decreased fetal levels. Disulfiram, for example, decreased Hg levels by a factor of 5. The 24 h values confirmed those at 4 h both elements, although the differences between control and treatment groups were less pronounced.Although the results suggest the formation of lipid-soluble metal-dithiocarbamate complexes in vivo (e.g., increased concentration in brain), this does not necessarily lead to increased fetal levels of the metals. The increased levels of Cd after thiram and DEDTC pretreatment, however, indicate a risk for higher Cd fetotoxicity. It is likely that Cd is released in fetal cells following metabolism of the dithiocarbamate moiety of the complex.     

Dithiocarbamate-induced biliary platinum excretion and the control of cis-platinum nephrotoxicity

Treatment with any one of six different dithiocarbamates subsequent to the administration of cis-platinum (CDDP) is shown to promote the biliary excretion of platinum. The administration of the most effective of these compounds, sodium diethyldithiocarbamate (DDTC) at 1.57 mmol/kg, led to a 30-fold increase in the biliary excretion of platinum. For the other dithiocarbamates investigated, a similar dosage led to increases ranging from approximately 5-fold for sodium iminodiacetic acid dithiocarbamate, to 26-fold for sodium sarcosine dithiocarbamate. The presence of alkyl groups on the nitrogen of the dithiocarbamate increased the effectiveness of the compounds. There is no increase in the platinum levels of the brain when DDTC is used in this manner. A histopathological evaluation of the kidneys of rats given 15 mg CDDP/kg in 6.3% saline with and without the use of dithiocarbamates for renal protection shows significant additional protection due to the use of the dithiocarbamates. Dithiocarbamates given at an appropriate dosing schedule can lead to a significant reduction in the renal damage which is revealed by microphotographs. It is suggested that part of the renal protection obtained by the use of dithiocarbamates may be due to this shift of platinum excretion to the bile which obviates additional renal exposure to platinum. It was also found that the simultaneous injection of a dithiocarbamate with the cis-platinum has no obvious effect on the anti-cancer action of cis-platinum against the Walker 256 carcinosarcoma in rats.     

Effects of dithiocarbamates on intestinal absorption and organ distribution of cadmium chloride in mice

Earlier publications have demonstrated that diethyldithiocarbamate (DDC) antagonizes the acute toxicity of injected CdCl2 but enhances the acute toxicity of orally administered CdCl2, most likely due to the high lipophilicity of DDC and the complex formed with the Cd++ ion. This study demonstrates that the hydrophilic dithiocarbamates dihydroxyethyldithiocarbamate (DHE-DTC) and N-methyl-N-glucamyl dithiocarbamate (NMG-DTC) also enhance the intestinal absorption of orally administered CdCl2 in mice, although less efficiently than DDC. After oral as well as intraperitoneal administration 15 min. after a single oral dose of CdCl2 the dithiocarbamates tested enhanced the intestinal cadmium uptake with a relative efficiency, DDC greater than DHE-DTC greater than NMG-DTC, which correlated to the lipophilicity of both the dithiocarbamates and the complexes formed with the Cd++ ion. Intraperitoneal administration of DDC induced extensive changes in the relative organ distribution of absorbed cadmium, compared to the distribution of CdCl2 administered alone. However, the only noticeable effect of administration of DHE-DTC and NMG-DTC was decreased gastrointestinal deposition of cadmium, irrespective of the administration route of the dithiocarbamates. Earlier studies have demonstrated that DDC and various other dithiocarbamates are capable of mobilizing intracellular cadmium deposits, presumably due to some lipophilicity. This study demonstrates that these dithiocarbamates may also enhance the intestinal absorption of cadmium.     

Placental transfer and fetal distribution of lead in mice after treatment with dithiocarbamates

The distribution of i.v. administered lead (²⁰³Pb-acetate; 50 nmol/kg b.w.) was studied by means of autoradiography and impulse counting in pregnant C57BL mice (day 18) treated orally with dithiocarbamates. Diethyldithiocarbamate (DEDTC), disulfiram or thiram (2×1 mmol/kg b.w.) or vehicle (gelatine) alone, was given by gavage 2 h before and immediately after the injection of lead. All three dithiocarbamates, especially thiram, changed the distribution pattern of lead. Thiram and DEDTC had the greatest effect at 4 h after lead administration, disulfiram at 24 h. In the mother, most notably the brain concentration increased (70-fold for thiram at 4 h) while that of erythrocytes and skeleton decreased (50- and 4-fold, respectively). The total fetal concentration unexpectedly showed only a moderate increase (2-fold for thiram), which may be due partly to the low maternal plasma lead concentration. The partition within the fetal tissues was, however, changed by the dithiocarbamates in much the same way as in the mothers, e.g., the fetal brain of thiram treated animals had increased by a factor 15, while skeletal and blood concentrations were lowered compared to controls. In melanin containing structures of the maternal and fetal eyes a dramatic increase in lead concentration resulted from dithiocarbamate treatment (lead ions are known to bind to melanin in vitro). The pattern of changes in lead distribution caused by dithiocarbamates is consistent with the formation in the body of lipid soluble lead-dithiocarbamate complexes that pass biological barriers more easily than lead inorganic (to brain, fetus, melanocytes etc.), probably followed by a dissociation of the complexes in the tissues.     

Effect of cytochrome P450 isozyme induction and glutathione depletion on the metabolism of CS2 to TTCA in rats

 Analysis of 2-thiothiazolidine-4-carboxylic acid (TTCA), a metabolite of carbon disulfide (CS₂), is used in the biological monitoring exposure to CS₂ at work. In order to clarify the metabolic reasons for individual variation in the urinary excretion of TTCA, the latter was studied in rats pretreated with model cytochrome P450 (CYP) enzyme inducers or glutathione (GSH) depletors. Ethanol, phenobarbital (PB) or 3-methylcholanthrene (MC) did not increase 24-h TTCA output following CS₂ inhalation (50 or 500 ppm, 6 h). After oral dosing (10 mg/rat), PB had an inhibiting effect on the excretion rate of TTCA. Tissue GSH depletors phorone, L-buthionine-(RS)-sulfoximine (BSO) and diethylmaleate (DEM) decreased TTCA excretion in rats given an oral dose (10 mg/rat) of CS₂. The initial inhibition by phorone and DEM was reversed after 6 h and from 12 h onward the TTCA in urine exceeded the control level, an effect not seen with BSO. The proportion of CS₂ excreted in urine as TTCA within 24 h was 1.7% in control rats and 1% after BSO treatment, 1.3% after PB, 1.7% after acetone, 1.8% after MC, 2.0% after phorone and 2.5% after DEM treatment. The amount of TTCA in urine increased with the CS₂ dose in a non-linear fashion: 1.6 μmol (50 ppm/6 h) vs. 4.9 μmol (500 ppm/6 h), and 0.2 μmol (1 mg/kg) versus 3.6 μmol (100 mg/kg). It is concluded that induction of different cytochrome P450 isoforms and transient glutathione depletion have only minor effects on the disposition of TTCA in rats following low-level CS₂ exposure persistently low glutathione level as achieved by E.G. BSO, markedly decreased the metabolism of CS₂ to TTCA; these metabolic effectors are unlikely to have a major role in the individual variation of CS₂ metabolism in exposed workers. Received: 14 June 1994/Accepted: 25 August 1994     

The relevance of 4,5-dihydroxy-2-hexanone in the excretion kinetics ofn-hexane metabolites in rat and man

Male Wistar rats were exposed ton-hexane concentrations between 50 and 3000 ppm for 8 h, and urinary excretion kinetics of then-hexane metabolites 1-hexanol, 2-hexanol, 3-hexanol, 2-hexanone, 2,5-hexanedione, and 4,5-dihydroxy-2-hexanone were assessed. The amounts of metabolites excreted were linearly dependent on then-hexane exposure concentration, up to an exposure of about 300 ppm. Above 300 ppm exposure the metabolite excretion indicated saturation kinetics in the metabolism ofn-hexane. In its quantity, the newly described 4,5-dihydroxy-2-hexanone was the second metabolite, its amount in the urine being about ten times higher than that of excreted 2,5-hexanedione. Using gas chromatography-mass spectrometry the occurrence of 4,5-dihydroxy-2-hexanone as ann-hexane metabolite in urine of man was confirmed after exposure of a male volunteer to a mean of 217 ppmn-hexane for 4 h (laboratory exposure). Twenty-six hours after starting this exposure the excretion of 4,5-dihydroxy-2-hexanone (as a result of then-hexane exposure) reached a level which was four times higher than the excretion of 2,5-hexanedione. The results in both rat and man indicate the relevance of 4,5-dihydroxy-2-hexanone as a metabolite ofn-hexane metabolism. Formation of this metabolite may be viewed as a route of detoxification.     

Structural effects in the dithiocarbamate-enhanced biliary excretion of cadmium

The dithiocarbamate enhancement of the biliary excretion of cadmium in rats loaded with cadmium (by either the oral or sc route) was found to be strongly dependent on the structure of the groups attached to the nitrogen atom of the dithiocarbamate moiety. Those dithiocarbamates containing hydroxyl-bearing attached groups were found to be capable of causing the greatest enhancement of the cadmium content of the bile. For the compounds of this type that were examined, this enhancement of biliary cadmium content varied from 30-fold to over 2000-fold. No enhancement of the biliary excretion of cadmium was found subsequent to the administration of sodium diethyldithiocarbamate, though this compound is known to cause a significant increase in the fecal excretion of cadmium.     

Protective effect of diethyldithiocarbamate and carbon disulfide against liver injury induced by various hepatotoxic agents

Diethyldithiocarbamate (DTC) and carbon disulfide (CS2), at nearly equimolar oral dose levels, protected mice against liver damage induced by carbon tetrachloride, chloroform, bromotrichloromethane, thioacetamide, bromobenzene, furosemide, acetaminophen, dimethylnitrosamine and trichloroethylene, as evidenced by the suppression of elevations in plasma GPT activity and liver calcium content, and of histopathological alterations. Both agents also prolonged hexobarbital sleeping time and zoxazolamine paralysis time in mice. DTC and SC, alone, given orally, decreased microsomal metabolism of several substrates (aniline, p-nitroanisole, hexobarbital, zoxazolamine, aminopyrine and 3,4-benzopyrene), CC14-induced lipid peroxidation, and cytochrome P-450 content. The loss of microsomal drug-metabolizing enzyme activity was also observed in the experiments in vitro using liver slices and isolated microsomes. Since a characteristic common to such diverse hepatotoxins is that they require metabolic activation before exhibiting hepatotoxicity, the protective mechanisms of DTC and CS2 may involve their interference with the process of metabolic activation of these hepatotoxins. The protective action of DTC may be mediated almost entirely through CS2 when administered orally and at least partly with parenteral administration, since, in CCl4-induced liver injury, DTC was most effective when given orally, while the action of CS2 was less dependent on the route of administration. Thus CS2 and CS2-producing agents in vivo such as dithiocarbamate derivatives and disulfiram may modify toxicological and pharmacological effects of foreign compounds by inhibiting microsomal drug-metabolizing enzyme activity in the liver.