Metabolism and toxicity of trichloroethylene and S-(1,2-dichlorovinyl)-L-cysteine in freshly isolated human proximal tubular cells

Trichloroethylene (Tri) caused modest cytotoxicity in freshly isolated huma n proximal tubular (hPT) cells, as assessed by significant decreases in lac tate dehydrogenase (LDH) activity after 1 h of exposure to 500 mu M Tri. Ox idative metabolism of Tri by cytochrome P-450 to form chloral hydrate (CH) was only detectable in kidney microsomes from one patient out of four teste d and was not detected in hPT cells. In contrast, GSH conjugation of Tri wa s detected in cells from every patient tested. The kinetics of Tri metaboli sm to its GSH conjugate S-(1,2-dichlorovinyl)glutathione (DCVG) followed bi phasic kinetics, with apparent K-m and V-max values of 0.51 and 24.9 mM and 0.10 and 1.0 nmol/min per mg protein, respectively. S-(1,2-dichlorovinyl)- L-cysteine (DCVC), the cysteine conjugate metabolite of Tri that is conside red the penultimate nephrotoxic species, caused both time- and concentratio n-dependent increases in LDH release in freshly isolated hPT cells. Preincu bation of hPT cells with 0.1 mM aminooxyacetic acid did not protect hPT cel ls from DCVC-induced cellular injury, suggesting that another enzyme beside s the cysteine conjugate beta-lyase may be important in DCVC bioactivation. This study is the first to measure the cytotoxicity and metabolism of Tri and DCVC in freshly isolated cells from the human kidney. These data indica te that the pathway involved in the cytotoxicity and metabolism of Tri in h PT cells is the GSH conjugation pathway and that the cytochrome P-450-depen dent pathway has little direct role in renal Tri metabolism in humans.