| Differences in the expression of drug metabolizing enzymes between cells of the rat and human kidney on chemical-induced nephrotoxicity were studied. Rat renal proximal tubular (rPT) and distal tubular (rDT) cells differed in their susceptibility to trichloroethylene (Tri) and thiophene-containing compounds. These differences were caused in part by differences in the activity of cytochrome P450 monooxygenase (P450) between the two cell types. Rpt cells expressed cytochrome P450 (CYP) 2B1/2, CYP2C11, CYP2E1, CYP4A2/3, and GSTα, but not CYP3A1/2, GSTμ, GSTπ, or GSTτ. rDT cells expressed CYP2B1/2, CYP2E1, and CYP4A2/3, GSTα, and GSTμ, but not CYP2C11, CYP3A1/2, GSTπ, or GSTτ. Expression of CYP2E1, was significantly higher in rDT cells than in rPT cells. Pyridine induced CYP2E1, in both liver and kidney microsomes but not in rPT and rDT cells. Clofibrate induced CYP4A and CYP2B only in liver and kidney microsomes and also CYP2E1 and CYP2C11 in kidney microsomes. The GST isoforms responsible for GSH conjugation of Tri were also determined. Pyridine treatment increased CH formation in rat liver and kidney microsomes. Clofibrate treatment only increased CH formation in kidney microsomes. Primary cultures of rPT and rDT cells maintained their expression of GSH-dependent enzymes but not P450 isoforms. Freshly isolated human proximal tubular (hPT) cells expresses CYP4A11, GSTA, GSTP, and GSTT but not GSTM. Tri and DCVC were toxic to freshly isolated hPT cells in a manner not affected by P450 or cysteine S-conjugate β-lyase inhibition. Tri was metabolized to its GSH conjugate but not to CH in hPT cells. Primary cultures of hPT cells maintained their expression of GSH-dependent enzymes and CYP4A11. Treatment of cultures with ethanol or dexamethasone altered expression of CYP4A11. These data support the hypothesis that differences in the susceptibility of rPT, rDT, and hPT cells to chemical-induced nephrotoxicity are caused by difference in the expression of drug metabolism enzymes. |