Oxidative stress in isolated rat renal proximal and distal tubular cells

Suspensions of purified proximal tubular (PT) and distal tubular (DT) cells were isolated from rat kidney cortical cells by Percoll density-gradient centrifugation and were used to investigate susceptibility of these regions of the nephron to oxidative injury. Exposure to tert-butyl hydroperoxide (tBH), menadione (MD), or H2O2 produced significantly greater cytotoxicity, as assessed by leakage of lactate dehydrogenase, in DT cells than in PT cells. The order of cytotoxic potency in both cell types was MD greater than tBH greater than H2O2. Preincubation of PT and DT cells with 5 mM glutathione (GSH) or 5 mM dithiothreitol delayed tBH-induced cytotoxicity, indicating a protective role of GSH. Addition of buthionine sulfoximine and acivicin with GSH, to inhibit GSH synthesis and degradation, eliminated the protective effect of GSH, indicating that protection by GSH in DT cells is not dependent on uptake of the intact tripeptide. Incubation of both PT and DT cells with tBH resulted in oxidation of GSH to glutathione disulfide. Activities of five detoxication enzymes were significantly higher in PT cells, indicating that a diminished ability to detoxify reactive metabolites may contribute to the higher intrinsic susceptibility of DT cells to oxidative injury.