Metabolism of the nephrotoxin dichloroacetylene by glutathione conjugation

Dichloroacetylene (DCA) is a potent nephrotoxin and nephrocarcinogen in rodents. The activation reactions responsible for this organ-specific toxicity are not known. We now report the identification of S-(1,2-dichlorovinyl)glutathione (DCVG) as a product of the glutathione (GSH) dependent metabolism of DCA in vitro and the identification of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (N-Ac-DCVC) as a urinary metabolite of DCA in rats. Formation of DCVG from DCA, used as 1:1 complex with diethyl ether, in male rat liver and kidney subcellular fractions was dependent on time, native protein, and the presence of GSH. Initial reaction rates at 23 degrees C were determined as 2923 nmol/(min.mg) for liver and 2838 nmol/(min.mg) for kidney microsomes. With cytosol, DCVG formation rates were 705 nmol/(min.mg) (liver cytosol) and 129 nmol/(min.mg) (kidney cytosol). With liver microsomes, a KM of 7.5 mM and a Vmax of 5464 nmol/(min.mg) for GSH were obtained. The product, DCVG, was definitively identified by 1H NMR spectrometry (400 MHz), mass spectrometry, and UV spectroscopy. N-Ac-DCVC was identified as a urinary metabolite from rats by GC/MS after esterification. Urine (collected for 24 h) from male rats exposed to 36 +/- 5 ppm DCA (100 mumol of DCA introduced into the exposure system) for 1 h contained 10.7 mumol of N-Ac-DCVC as determined by HPLC analysis. Formation of DCVG, renal processing to S-(1,2-dichlorovinyl)-L-cysteine, and cleavage of this cysteine S-conjugate by cysteine S-conjugate beta-lyase in the kidney with formation of reactive and mutagenic intermediates may account for DCA nephrotoxicity and nephrocarcinogenicity.(ABSTRACT TRUNCATED AT 250 WORDS)