Diquat induces renal proximal tubule injury in glutathione reductase-deficient mice

Reactive oxygen species (ROS) have been associated with many human diseases, and glutathione (GSH)-dependent processes are pivotal in limiting tissue damage. To test the hypothesis that Gr1a1Neu (Neu) mice, which do not express glutathione reductase (GR), would be more susceptible than are wild-type mice to ROS-mediated injury, we studied the effects of diquat, a redox cycling toxicant. Neu mice exhibited modest, dose- and time-dependent elevations in plasma alanine aminotransferase (ALT) activities, 126 ± 36 U/l at 2 h after 5 μmol/kg of diquat, but no ALT elevations were observed in diquat-treated C3H/HeN mice for up to 6 h after 50 μmol/kg of diquat. Histology indicated little or no hepatic necrosis in diquat-treated mice of either strain, but substantial renal injury was observed in diquat-treated Neu mice, characterized by brush border sloughing in the proximal tubules by 1 h and tubular necrosis by 2 h after doses of 7.5 μmol/kg. Decreases in renal GSH levels were observed in the Neu mice by 2 h post dose (3.4 ± 0.4 vs 0.2 ± 0.0 μmol/g tissue at 0 and 50 μmol/kg, respectively), and increases in renal GSSG levels were observed in the Neu mice as early as 0.5 h after 7.5 μmol/kg (105.5 ± 44.1 vs 27.9 ± 4.8 nmol/g tissue). Blood urea nitrogen levels were elevated by 2 h in Neu mice after doses of 7.5 μmol/kg (Neu vs C3H, 32.8 ± 4.1 vs 17.9 ± 0.3 mg/dl). Diquat-induced renal injury in the GR-deficient Neu mice offers a useful model for studies of ROS-induced renal necrosis and of the contributions of GR in defense against oxidant-mediated injuries in vivo.