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.

Chloropicrin dechlorination in relation to toxic action.

Chloropicrin (CCl3NO2) is a widely used soil fumigant with an unknown mechanism of acute toxicity. We investigated the possible involvement of dechlorination in CCl3NO2 toxicity by considering its metabolism, inhibition of pyruvate and succinate dehydrogenases, cytotoxicity in cultured cells, and interaction with hemoproteins. In a newly discovered pathway, CCl3NO2 is metabolized to thiophosgene, which is characterized as the cyclic cysteine adduct (raphanusamic acid) in the urine of mice. CCl3NO2 inhibits porcine heart pyruvate dehydrogenase complex (IC-50 4 microM) and mouse liver succinate dehydrogenase complex (IC-50 13 microM), whereas its dehalogenated metabolites (CHCl2NO2 and CH2ClNO2) are more than 10 times less effective. The inhibitory potency of CCl3NO2 for these dehydrogenase complexes is similar to that of captan, folpet, and dichlone fungicides (IC-50 2-6 microM). CCl3NO2 cytotoxicity with Hepa 1c1c7+ mouse hepatoma cells (IC-50 9 microM) is not correlated with glutathione depletion. Mice treated intraperitoneally with CCl3NO2 at 50 mg/kg but not with an equivalent dose of CHCl2NO2 show increased concentrations of oxyhemoglobin in liver. The acute toxicity of CCl3NO2 in mice is due to the parent compound or metabolites other than CHCl2NO2 or CH2ClNO2 and may be associated with inhibition of the pyruvate dehydrogenase complex and elevated oxyhemoglobin.