Metabolism of the nephrotoxin dichloroacetylene by glutathione conjugation

Publisher Website
Google Scholar
Abstract
Dichloroacetylene (DCA) is a potent nephrotoxin and nepharocarcinogen 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 metabolsim 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 diethly ether, im male rat liver and kidney subcellular fractions was dependent on time, native protein, and the presence of GSH. Initial reaction rates at 23.degree.C were determined as 2923 nmol/(min .cntdot. mg) for liver and 2838 nmol/(min .cntdot. mg) for kidney microsomes. With cytosol, DCVG formation rates were 705 nmol/(min .cntdot. mg) (liver cytosol) and 129 nmol/(min .cntdot. mg) (kidney cytosol). With liver microsomes, a KM of 7.5 mm and a Vmax of 5464 nmol/(min .cntdot. mg) for GSH were obtained. The product, DCVG, was definitively identified by 1H NMR spectrometry (400 MHz), mass spectrometry, and UV spectrometery, 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 exosed to 36 .+-. 5 ppm DCA (100 .mu.mol of DCA introduced into the exposure system) for 1h contained 10.7 .mu.mol 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. N-Ac-DCVC is the end product of DCVG processing by the enzymes of mercapturic acid formation.