PT - JOURNAL ARTICLE AU - Lawrence H. Lash AU - John C. Lipscomb AU - David A. Putt AU - Jean C. Parker TI - Glutathione Conjugation of Trichloroethylene in Human Liver and Kidney: Kinetics and Individual Variation DP - 1999 Mar 01 TA - Drug Metabolism and Disposition PG - 351--359 VI - 27 IP - 3 4099 - http://dmd.aspetjournals.org/content/27/3/351.short 4100 - http://dmd.aspetjournals.org/content/27/3/351.full SO - Drug Metab Dispos1999 Mar 01; 27 AB - Isolated human hepatocytes exhibited time-, trichloroethylene (Tri) concentration-, and cell concentration-dependent formation ofS-(1,2-dichlorovinyl)glutathione (DCVG) in incubations in sealed flasks with 25 to 10,000 ppm Tri in the headspace, corresponding to 0.011 to 4.4 mM in hepatocytes. Maximal formation of DCVG (22.5 ± 8.3 nmol/120 min per 106 cells) occurred with 500 ppm Tri. Time-, protein concentration-, and both Tri and GSH concentration-dependent formation of DCVG were observed in liver and kidney subcellular fractions. Two kinetically distinct systems were observed in both cytosol and microsomes from pooled liver samples, whereas only one system was observed in subcellular fractions from pooled kidney samples. Liver cytosol exhibited apparentKm values (μM Tri) of 333 and 22.7 andVmax values (nmol DCVG formed/min per mg protein) of 8.77 and 4.27; liver microsomes exhibited apparentKm values of 250 and 29.4 andVmax values of 3.10 and 1.42; kidney cytosol and microsomes exhibited apparent Km values of 26.3 and 167, respectively, and Vmaxvalues of 0.81 and 6.29, respectively. DCVG formation in samples of liver cytosol and microsomes from 20 individual donors exhibited a 6.5-fold variation in microsomes but only a 2.4-fold variation in cytosol. In coincubations of pooled liver cytosol and microsomes, addition of an NADPH-regenerating system produced marked inhibition of DCVG formation, but addition of GSH had no effect on cytochrome P-450-catalyzed formation of chloral hydrate. These results indicate that both human kidney and liver have significant capacity to catalyze DCVG formation, indicating that the initial step of the GSH-dependent pathway is not limiting in the formation of nephrotoxic and nephrocarcinogenic metabolites. The American Society for Pharmacology and Experimental Therapeutics