Role of cytochrome P450 and glutathione S-transferase alpha in the metabolism and cytotoxicity of trichloroethylene in rat kidney

The toxicity and metabolism of trichloroethylene (TRI) were studied in rena l proximal tubular (PT) and distal tubular (DT) cells from male Fischer 344 rats. TRI was slightly toxic to both PT and DT cells, and inhibition of cy tochrome P450 (P450; substrate, reduced-flavoprotein:oxygen oxidoreductase [RH-hydroxylating or -epoxidizing]; EC 1.14.14.1) increased TRI toxicity on ly in:DT cells. In untreated cells, glutathione (GSH) conjugation of TRI to form S-(1,2-dichlorovinyl)glutachione (DCVG) was detected only in PT cells . Inhibition of P450 transiently increased DCVG formation in PT cells and r esulted in detection of DCVG formation in DT cells. Formation of DCVG in PT cells was described by a two-component model (apparent V-max values of 0.6 5 and 0.47 nmol/min per mg protein and K-m values of 2.91 and 0.46 mM). Cyt osol isolated from rat renal cortical, PT, and DT cells expressed high leve ls of GSH S-transferase (GST; RX:glutathione R-transferase; EC 2.5.1.18) al pha (GST alpha) but not GST pi. Low levels of GST mu were detected in corti cal and DT cells. Purified rat GST alpha 2-2 exhibited markedly higher affi nity for TRI than did GST alpha 1-1 or GSTT alpha 1-2, but each isoform exh ibited similar V-max values. Triethyltinbromide (TETB) (9 mu M) inhibited D CVG formation by purified GST alpha 1-1 and GST alpha 2-2, but not GST alph a 1-2; Bromosulfophthalein (BSP) (4 mu M) only inhibited DCVG formation by GST alpha 2-2.TETB and BSP inhibited approximately 90% of DCVG formation in PT cytosol but had no effect in DT cytosol. This suggests that GST alpha 1 -1 is the primary isoform in rat renal PT cells responsible for GSH conjuga tion of TRI. These data, for the first time, describe the metabolism of TRI by individual GST isoforms and suggest that DCVG feedback inhibits TRI met abolism by GSTs. (C) 2000 Elsevier Science Inc.