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Biomedical subjects

W Dekant

Publications and source records attributed to W Dekant.

At least 109 records · Page 6Linked to original sources
PubMed1989

Assessment of unscheduled DNA synthesis in a cultured line of renal epithelial cells exposed to cysteine S-conjugates of haloalkenes and haloalkanes.

The ability of S-(1,2-dichlorovinyl)-L-cysteine (DCVC), S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC), S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine (PCBC), S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFEC) and S-(2-chloroethyl)-L-cysteine (CEC) to induce DNA repair was investigated in LLC-PK1, a cultured line of porcine kidney tubular epithelial cells. DNA repair due to exposure of the cells to the S-conjugates was determined as unscheduled DNA synthesis (UDS) after inhibition of replicative DNA synthesis in confluent LLC-PK1 monolayers. DCVC, TCVC and PCBC induced dose-dependent UDS in LLC-PK1 at concentrations which did not impair the viability of the cells compared to untreated controls; higher concentrations were cytotoxic, resulting in lactate dehydrogenase leakage into the medium. Cell death was also induced by CTFEC, which failed to exert genotoxicity. CEC induced the highest response among these cysteine conjugates without impairing cell viability. Inhibition of cysteine conjugate beta-lyase with aminooxyacetic acid abolished the effects of DCVC, TCVC, PCBC and CTFEC but did not influence the genotoxicity of CEC.

Animals↗
PubMed1989

Covalent binding of hexachlorobutadiene metabolites to renal and hepatic mitochondrial DNA.

The covalent binding of [14C]hexachlorobutadiene (HCBD) metabolites to DNA was investigated in mouse liver and kidney after application of a single oral dose of 30 mg/kg. A low level of binding of [14C]HCBD metabolites to nuclear DNA (nDNA) from kidney with a covalent binding index (CBI) of 27 was detectable, whereas nDNA from liver did not retain radioactivity significantly exceeding background activity (background CBInDNA = 6 and CBImtDNA = 60). Considerably higher binding of metabolites to mitochondrial DNA (mtDNA) from liver (CBI = 500) and kidney (CBI = 7500) could be demonstrated. Enzymatic hydrolysis followed by HPLC fractionation of mtDNA from mouse kidney revealed the presence of three radioactive compounds which may represent DNA bases altered by HCBD metabolites. The observed binding of HCBD metabolites to DNA constituents in vivo suggests that genotoxic mechanisms are operative in initiating HCBD nephrocarcinogenesis.

Animals↗
PubMed1988

Induction of unscheduled DNA synthesis and micronucleus formation in Syrian hamster embryo fibroblasts treated with cysteine S-conjugates of chlorinated hydrocarbons.

S-(chloroethyl)-cysteine (CEC) and S-(1,2-dichlorovinyl)-cysteine (DCVC) have been proposed as intermediates in the metabolic transformation of the carcinogens 1,2-dichloroethane and 1,1,2-trichloroethylene. We have tested the ability of CEC and DCVC to induce DNA repair and genotoxic effects at the chromosomal level by comparative assessment of unscheduled DNA synthesis induction and micronucleus formation in Syrian hamster embryo fibroblasts. CEC induced a potent and dose-dependent response in both assays, whereas DCVC treatment resulted in a comparatively weak induction of DNA repair and failed to raise micronucleus formation above control rates. Inhibition of cysteine conjugate beta-lyase diminished the effect of DCVC, but had no influence on the genotoxicity of CEC either in the unscheduled DNA synthesis or micronucleus assay.

Animals↗
PubMed1988

Bacterial cysteine conjugate beta-lyase and the metabolism of cysteine S-conjugates: structural requirements for the cleavage of S-conjugates and the formation of reactive intermediates.

The cysteine conjugate beta-lyase mediated metabolism and the mutagenicity of the synthetic cysteine conjugates S-(2-chloroethyl)-L-cysteine (CEC), S-(2-chlorovinyl)-L-cysteine (CVC), S-(1,2,3,3,3-pentachloroprop-1-enyl)-L-cysteine (PCPC), S-(pentachlorophenyl)-L-cysteine (PCPhC), S-(chloro-1,2,2-trifluoroethyl)-L-cysteine (CTFEC), S-benzyl-L-cysteine (SBC) and S-methyl-L-cysteine (SMC) were investigated in Salmonella typhimurium strains TA100, TA2638, TA102 and TA98 to establish structure/activity relationships. Bacterial 100,000 X g supernatants cleaved CTFEC, PCPC, CVC, PCPhC and SBC to pyruvate; pyruvate formation was inhibited by the beta-lyase inhibitor aminooxyacetic acid (AOAA) in all cases. Of the compounds tested, CEC, PCPC and CVC were mutagenic in the Ames-test. CTFEC, PCPhC and SBC failed to increase the number of revertants above control levels. The mutagenicity of PCPC and CVC could be inhibited by AOAA. CEC exerted a potent mutagenic effect in the Ames-test which was not affected by AOAA; CEC was not transformed to pyruvate by bacterial beta-lyase. Neither pyruvate formation nor mutagenicity were observed with SMC. These results indicate that the structure of the substituent on the sulfur atom is an important determinant for the biological activity of cysteine S-conjugates. Electronegative and/or unsaturated substituents are required for beta-lyase catalysed beta-elimination reactions. The formation of chemically unstable thiols, which may be converted to thioacylating intermediates, seems to be a prerequisite for beta-lyase dependent mutagenicity of S-conjugates.

Aminooxyacetic Acid↗
PubMed1988

Thioacylating agents as ultimate intermediates in the beta-lyase catalysed metabolism of S-(pentachloro-butadienyl)-L-cysteine.

The transformation of the hexachloro-1,3-butadiene metabolite S-(1,2,3,4,4-pentachlorobuta-1,3-dienyl)-L-cysteine (PCBC) by bacterial cysteine conjugate beta-lyase (beta-lyase) and by N-dodecylpyridoxal bromide (PLP-Br) was investigated using GC/MS to identify products formed. PCBC was transformed by both bacterial beta-lyase and PLP-Br to the major products 2,3,4,4-tetrachlorobutenoic acid and 2,3,4,4-tetrachlorothiobutenoic acid, and to the minor metabolites trichloroacetic acid and S-(1,2,3,4,4-pentachlorobuta-1,3-dienyl)-mercaptoacetic acid. In the presence of diethylamine as model nucleophile, PLP-Br transformed PCBC to yield 2,3,4,4-tetrachlorothiobutenoic acid diethylamide; attempts to trap 1,2,3,4,4-pentachlorobutadienyl thiol, the initial metabolite formed by beta-elimination from PCBC, were unsuccessful. The results obtained suggest that the formation of a thioacylating intermediate (a thioketene or a thiono acyl chloride) may be the decisive reaction during the beta-lyase dependent activation of PCBC.

Butadienes↗
PubMed1988

Mutagenicity of amino acid and glutathione S-conjugates in the Ames test.

The mutagenicity of the glutathione S-conjugate S-(1,2-dichlorovinyl)glutathione (DCVG), the cysteine conjugates S-(1,2-dichlorovinyl)-L-cysteine (DCVC) and S-(1,2-dichlorovinyl)-DL-alpha-methylcysteine (DCVMC), and the homocysteine conjugates S-(1,2-dichlorovinyl)-L-homocysteine (DCVHC) and S-(1,2-dichlorovinyl)-DL-alpha-methylhomocysteine (DCVMHC) was investigated in Salmonella typhimurium strain TA2638 with the preincubation assay. DCVC was a strong, direct-acting mutagen; the cysteine conjugate beta-lyase inhibitor aminooxyacetic acid decreased significantly the number of revertants induced by DCVC; rat renal mitochondria (11,000 X g pellet) and cytosol (105,000 X g supernatant) with high beta-lyase activity increased DCVC mutagenicity at high DCVC concentrations. DCVG was also mutagenic without the addition of mammalian activating enzymes; the presence of low gamma-glutamyltransferase activity in bacteria, the reduction of DCVG mutagenicity by aminooxyacetic acid, and the potentiation of DCVG mutagenicity by rat kidney mitochondria and microsomes (105,000 X g pellet) with high gamma-glutamyltransferase activity indicate that gamma-glutamyltransferase and beta-lyase participate in the metabolism of DCVG to mutagenic intermediates. The homocysteine conjugate DCVHC was only weakly mutagenic in the presence of rat renal cytosol, which exhibits considerable gamma-lyase activity, this mutagenic effect was also inhibited by aminooxyacetic acid. The conjugates DCVMC and DCVMHC, which are not metabolized to reactive intermediates, were not mutagenic at concentrations up to 1 mumole/plate. The results demonstrate that gamma-glutamyltransferase and beta-lyase are the key enzymes in the biotransformation of cysteine and glutathione conjugates to reactive intermediates that interact with DNA and thereby cause mutagenicity.

Acetylcysteine↗
PubMed1988

Mutagenicity of hexachloro-1,3-butadiene and its S-conjugates in the Ames test--role of activation by the mercapturic acid pathway in its nephrocarcinogenicity.

The mutagenicity of hexachloro-1,3-butadiene and its S-conjugates 1-(glutathion-S-yl)-1,2,3,4,4-pentachloro-1,3-butadiene (GTB), 1,4-(bis-glutathion-S-yl-1,2,3,4-tetrachloro-1,3-butadiene (BGTB) and 1,4-(bis-cystein-S-yl)-1,2,3,4-tetrachloro-1,3-butadiene (BCTB) was investigated in Salmonella typhimurium TA100 using a modified preincubation assay. GTB was a direct-acting mutagen; the mutagenic potency of GTB was markedly enhanced by rat kidney microsomes or mitochondria and less so by cytosol. The bis-conjugates BGTB and BCTB were not mutagenic in the strains TA100, TA2638 and TA98. Purified HCBD was not mutagenic either without exogenous metabolic activation or with rat liver microsomes fortified with NADPH. Preincubation with rat liver microsomes and glutathione resulted in an unequivocal mutagenic activity of HCBD which was increased by additional inclusion of rat kidney microsomes. The cysteine conjugate beta-lyase inhibitor aminooxyacetic acid decreased the mutagenicity of HCBD and its S-conjugates. These results provide strong evidence that formation of the corresponding monoglutathione S-conjugate from HCBD and subsequent cleavage of this conjugate by gamma-glutamyltranspeptidase and beta-lyase may be responsible for the nephrocarcinogenicity of the parent compound in vivo, whereas formation of the bis-glutathione S-conjugate probably plays no role in the organ specific effects of HCBD.

Aminooxyacetic Acid↗
PubMed1988

DNA-binding of sulfur-containing metabolites from 35S-(pentachlorobutadienyl)-L-cysteine in bacteria and isolated renal tubular cells.

S-(Pentachlorobutadienyl)-L-cysteine (PCBC) is the penultimate metabolite formed from the nephrocarcinogen hexachlorobutadiene (HCBD). It is activated by cysteine conjugate beta-lyase (beta-lyase) to yield thioacylating metabolites thought to be responsible for PCBC-induced cytotoxicity and mutagenicity. We have investigated the beta-lyase dependent DNA-binding of metabolites formed from 35S-PCBC in Salmonella typhimurium (S. typhimurium) TA100 and in rat renal proximal tubule cells. 35Sulfur was found in DNA isolated from S. typhimurium (410 +/- 93 DNA-adducts per 10(6) nucleotides) and renal cells (68 or 97 DNA-adducts per 10(6) nucleotides). Enzymatic hydrolysis of the isolated DNA to yield 3'-nucleotide phosphates and fractionation of the hydrolysate by HPLC indicated the presence of 3 distinct, 35S-containing metabolites which did not coelute with unchanged 3'-nucleotide phosphates and likely represent DNA constituents modified by 35S-PCBC metabolites. Identical retention volumes were obtained for altered bases isolated from bacteria and from renal cells. The results obtained indicate that PCBC metabolites may covalently bind to DNA and implicate genotoxic mechanisms in HCBD-induced nephrocarcinogenicity.

Animals↗
PubMed1988

Metabolism of hexachloro-1,3-butadiene in mice: in vivo and in vitro evidence for activation by glutathione conjugation.

1. The metabolism of 14C-hexachloro-1,3-butadiene (HCBD) was studied in mice and in subcellular fractions from mouse liver and kidney. 2. In the presence of glutathione (GSH), liver microsomes and cytosol transformed HCBD to S-(pentachlorobutadienyl)glutathione (PCBG). PCBG formation in subcellular fractions from mouse kidney was very limited. Oxidative metabolism of HCBD by cytochrome P-450 could not be demonstrated. 3. Cysteine conjugate beta-lyase was present in mitochondria and cytosol from mouse liver and kidney. 4. After an oral dose of 30 mg/kg 14C-HCBD, mice eliminated 67.5-76.7% of dose in faeces; urinary elimination accounted for 6.6-7.6%. 5. Metabolites of HCBD identified are: S-(pentachlorobutadienyl)glutathione in faeces; S-(pentachlorobutadienyl)-L-cysteine, N-acetyl-S-(pentachlorobutadienyl)-L-cysteine and 1,1,2,3-tetrachlorobutenoic acid in urine. 6. The results suggest that conjugation of HCBD with GSH in liver, followed by renal processing of the glutathione S-conjugates and beta-lyase-catalysed formation of reactive intermediates, accounts for the organ specific toxicity of HCBD in mice.

Animals↗
PubMed1988

Biosynthesis and biotransformation of glutathione S-conjugates to toxic metabolites.

The material presented in this review deals with the hypothesis that the nephrotoxicity of certain halogenated alkanes and alkenes is associated with hepatic biosynthesis of glutathione S-conjugates, which are further metabolized to the corresponding cysteine S-conjugates. Some glutathione or cysteine S-conjugates may be direct-acting nephrotoxins, but most cysteine S-conjugates require bioactivation by renal, pyridoxal phosphate-dependent enzymes, such as cysteine conjugate beta-lyase (beta-lyase). The biosynthesis of glutathione S-conjugates is catalyzed by both the cytosolic and the microsomal glutathione S-transferases, although the latter enzyme is a better catalyst for the reaction of haloalkenes with glutathione. When glutathione S-conjugate formation yields sulfur mustards, as occurs with vicinal-dihaloethanes, the S-conjugates are direct-acting toxins. In contrast, the S-conjugates formed from fluoro- and chloroalkenes yield S-alkyl- or S-vinyl glutathione conjugates, respectively, which are metabolized to the corresponding cysteine S-conjugates by gamma-glutamyltransferase and dipeptidases; inhibition of these enzymes blocks the toxicity of the glutathione S-conjugates. The cysteine S-conjugates must be metabolized by beta-lyase for the expression of toxicity; the beta-lyase inhibitor aminooxyacetic acid blocks the toxicity of cysteine S-conjugates, and the corresponding alpha-methyl cysteine S-conjugates, which cannot be metabolized by beta-lyase, are not toxic. Moreover, probenecid, an inhibitor of renal anion transport system, blocks the toxicity of cysteine S-conjugates, which cannot be metabolized by beta-lyase, are not toxic. Moreover, probenecid, an inhibitor of renal anion transport system, blocks the toxicity of cysteine S-conjugates. Homocysteine S-conjugates are also potent cyto- and nephrotoxins. The high renal content of gamma-glutamyltransferase and the renal anion transport system are probably determinants of kidney tissue as a target site. Biochemical studies indicate that renal mitochondrial dysfunction is produced by the cysteine S-conjugates. Finally, some of the glutathione and cysteine conjugates are mutagenic in the Ames test, and reactive intermediates formed by the action of beta-lyase may contribute to the nephrocarcinogenicity of certain chloroalkenes.

Animals↗
PubMed1988

Metabolism and excretion of S-conjugates derived from hexachlorobutadiene in the isolated perfused rat kidney.

Renal processing of the S-conjugates derived from hexachlorobutadiene (HCBD), S-(pentachlorobutadienyl)glutathione (PCBG), and S-(pentachlorobutadienyl)-L-cysteine (PCBC) was studied in the isolated perfused rat kidney. At an initial perfusate concentration of 20 microM, both conjugates were rapidly eliminated from the perfusate. Calculation of the fractional clearance rates revealed the dominant role of nonfiltering mechanisms in this process. This was confirmed by the strong inhibitory effect of 50 microM probenecid. S-(Pentachlorobutadienyl)-N-acetyl-L-cysteine (N-Ac-PCBC) was detected as the major metabolite of both PCBG and PCBC in urine and perfusate. PCBC and S-(pentachlorobutadienyl)cysteinylglycine were minor urinary metabolites formed from PCBG; only N-Ac-PCBC and PCBC were detected in the perfusate. At an initial S-conjugate concentration of 100 microM in the perfusate, the rate of elimination of both PCBG and PCBC continuously decreased during the perfusion, mainly as the result of a reduced excretion of N-Ac-PCBC. This indicates marked disturbance of N-acetylation and/or transport under these conditions. Addition of probenecid resulted in a significantly reduced renal elimination of both S-conjugates, predominantly due to a reduced rate of mercapturate excretion. In contrast, the nephrotoxicity of PCBC or PCBG was not significantly influenced by probenecid. It is concluded from these experiments that the kidney has the capacity to metabolize HCBD S-conjugates and that nonfiltering excretion of the mercapturic acid plays a decisive role. The pathways of HCBD S-conjugate metabolism in the kidney were shown to be dependent on their initial concentrations in the perfusate, most probably as a consequence of concentration-dependent toxic disturbances of transport and/or N-acetylation.

Acetylation↗
PubMed1987

Enzymatic transformation of mercapturic acids derived from halogenated alkenes to reactive and mutagenic intermediates.

The metabolism of the mercapturic acids S-pentachlorobutadienyl-N-acetylcysteine (N-Ac-PCBC), S-trichlorovinyl-N-acetylcysteine (N-Ac-TCVC) and S-dichlorovinyl-N-acetylcysteine (N-Ac-DCVC) by subcellular fractions from male rat liver and kidney homogenates was studied. As a model compound, N-Ac-PCBC, 14C labelled, was synthesised. It was intensively metabolised by cytosolic but not by microsomal enzymes from rat liver and kidney. The major metabolite identified by GC/MS was pentachlorobutadienylcysteine, the amount produced being highest in kidney cytosol. Metabolic conversion of 14C-N-Ac-PCBC by kidney and liver cytosol resulted in covalent binding of radioactivity to protein, binding was strongly inhibited by the beta-lyase inhibitor aminooxyacetic acid (AOAA). N-Ac-TCVC and N-Ac-DCVC were also transformed by cytosolic enzymes to the corresponding cysteine conjugates (trichlorovinylcysteine and dichlorovinylcysteine). The three mercapturic acids tested were strong mutagens in the Ames-test after addition of rat kidney cytosol. In the absence of cytosol, N-Ac-TCVC and N-Ac-DCVC were weakly but definitely mutagenic, whereas N-Ac-PCBC was not. In contrast to N-Ac-PCBC, the "direct" mutagens N-Ac-TCVC and N-Ac-DCVC were both transformed to pyruvate by bacterial (S. typhimurium TA100) homogenate 100,000 g supernatants. It is concluded that mercapturic acids are deacetylated to the corresponding cysteine conjugates by cytosolic (N-Ac-PCBC, N-Ac-TCVC and N-Ac-DCVC) and bacterial enzymes (N-Ac-TCVC and N-Ac-DCVC) and further cleaved to reactive and mutagenic intermediates by mammalian and/or bacterial beta-lyase. The observed activation mechanisms for the mercapturic acids, whose formation from hexachlorobutadiene, tetrachloroethylene and trichloroethylene has been proven, might contribute to the nephrotoxicity and nephrocarcinogenicity of the parent alkenes.

Acetylation↗
PubMed1987

Bioactivation mechanism of the cytotoxic and nephrotoxic S-conjugate S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine.

The bioactivation of S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFC) was studied with purified bovine kidney cysteine conjugate beta-lyase and with N-dodecylpyridoxal bromide in cetyltrimethylammonium bromide micelles as a pyridoxal model system. The beta-lyase and the pyridoxal model system converted CTFC to chlorofluoroacetic acid and inorganic fluoride, which were identified by 19F NMR spectrometry. 2-Chloro-1,1,2-trifluoroethanethiol and chlorofluorothionoacetyl fluoride were formed as metabolites of CTFC and were trapped with benzyl bromide and diethylamine, respectively, to yield benzyl 2-chloro-1,1,2-trifluoroethyl sulfide and N,N-diethyl chlorofluorothioacetamide, which were identified by gas chromatography/mass spectrometry. The bioactivation mechanism of CTFC therefore involves the initial formation of the unstable thiol 2-chloro-1,1,2-trifluoroethanethiol, which loses hydrogen fluoride to form the acylating agent chlorofluorothionoacetyl fluoride; hydrolysis of the thionoacyl fluoride affords the stable, terminal metabolites chlorofluoroacetic acid and inorganic fluoride. The intermediate acylating agent and chlorofluoroacetic acid may contribute to the cytotoxic effects of CTFC.

Animals↗
PubMed1986

Bacterial beta-lyase mediated cleavage and mutagenicity of cysteine conjugates derived from the nephrocarcinogenic alkenes trichloroethylene, tetrachloroethylene and hexachlorobutadiene.

The metabolism of beta-lyase and the mutagenicity of the synthetic cysteine conjugates S-1,2-dichlorovinylcysteine (DCVC), S-1,2,2-trichlorovinylcysteine (TCVC), S-1,2,3,4,4-pentachlorobuta-1,3-dienylcysteine (PCBC) and S-3-chloropropenylcysteine (CPC) were investigated in Salmonella typhimurium strains TA100, TA2638 and TA98. The bacteria contained significantly higher concentrations of beta-lyase than mammalian subcellular fractions. Bacterial 100,000 X g supernatants cleaved benzthiazolylcysteine to equimolar amounts of mercaptobenzthiazole and pyruvate. DCVC, TCVC and PCBC produced a linear time-dependent increase in pyruvate formation when incubated with bacterial 100,000 X g supernatants; pyruvate formation was inhibited by the beta-lyase inhibitor aminooxyacetic acid (AOAA). CPC was not cleaved by bacterial enzymes to pyruvate. DCVC, TCVC and PCBC were mutagenic in three strains of S. typhimurium (TA100, TA2638 and TA98) in the Ames-test without addition of mammalian subcellular fractions; their mutagenicity was decreased by the addition of AOAA to the preincubation mixture. CPC was not mutagenic in any of the strains of bacteria tested. These results indicate that beta-lyase plays a key role in the metabolism and mutagenicity of haloalkenylcysteines when tested in S. typhimurium systems. The demonstrated formation in mammals of the mutagens DCVC, TCVC and PCBC during biotransformation of trichloroethylene (Tri), tetrachloroethylene (Tetra) and hexachlorobutadiene (HCBD) may provide a molecular explanation for the nephrocarcinogenicity of these compounds.

Animals↗
PubMed1986

Mutagenicity of chloroolefins in the Salmonella/mammalian microsome test--II. Structural requirements for the metabolic activation of non-allylic chloropropenes and methylated derivatives via epoxide formation.

Non-allylic chloropropenes and their methyl-homologues, being chloro-substituted exclusively in vinylic position, are mutagenic in the presence of metabolizing rat liver homogenate fraction (S9 mix). This can be interpreted as the result of polarizing inductive (I-) and mesomeric (M-) effects exerted by Cl- as well as by CH3-substituents on the olefinic double bond. The extent of their mutagenic activity increases with longer preincubation time and/or a higher concentration of rat liver homogenate fraction (S9) in the S9 mix. The only exception from this rule of a qualitative correlation of C = C-bond polarization due to asymmetric substitution and mutagenic activity is 1-chloro-2-methyl-1-propene which is non-mutagenic. In this case effects of a steric hindrance of two voluminous CH3-substituents attached to one C-atom of the C = C-bond might inhibit enzymatic attack of the double bond by microsomal oxygenase. Mutagenic activity is invariably decreased in the presence of SKF525, inhibitor of microsomal oxygenase, and increased when 1,1,1-trichloropropene-2,3-oxide (TCPO), inhibitor of epoxide hydrolase, is added to the test system. This is a strong argument for metabolic activation of these substances occurring via epoxide formation.

Alkenes↗
PubMed1986

Identification of S-1,2,2-trichlorovinyl-N-acetylcysteine as a urinary metabolite of tetrachloroethylene: bioactivation through glutathione conjugation as a possible explanation of its nephrocarcinogenicity.

The elimination and metabolism of [14-C]-tetrachloroethylene (Tetra) was studied in female rats and mice after the oral administration of 800 mg/kg [14-C]-Tetra. Elimination of unchanged Tetra was the main pathway of elimination in both species and amounted to 91.2% of the dose in rats and 85.1% in mice. [14-C]-Carbon dioxide (CO2) was found to be a trace metabolite of [14-C]-Tetra. Only a small part of the applied dose was transformed to urinary (rats = 2.3%, mice = 7.1%) and fecal (rats = 2.0%, mice = 0.5%) metabolites. The urinary metabolites were separated and quantified by high performance liquid chromatography (HPLC) and identified by gas liquid chromatography/mass spectrometry (GC/MS). The following metabolites could be identified: oxalic acid (8.0% of urinary radioactivity in rats, 2.9% in mice), dichloroacetic acid (5.1%, 4.4%), trichloroacetic acid (54.0%, 57.8%), N-trichloroacetyl-aminoethanol (5.4%, 5.7%), trichloroethanol, free and conjugated (8.7%, 8.0%), S-1,2,2-trichlorovinyl-N-acetylcysteine (N-acetyl TCVC) (1.6%, 0.5%), and another conjugate of trichloroacetic acid (1.8%, 1.3%). The structures of the identified metabolites indicate two different pathways operative in Tetra biotransformation: cytochrome P-450-mediated epoxidation forming reactive metabolites in the liver and conjugation of Tetra with glutathione (GSH) catalyzed by glutathione transferase(s). The formation of reactive intermediates by renal processing of the glutathione conjugates may provide a molecular mechanism for the nephrotoxicity and nephrocarcinogenicity of Tetra in male rats.

Acetylcysteine↗