RESUMO
<p><b>OBJECTIVE</b>To explore the effects of chronic exposure to trace chromium (VI) as a result of metal-on-metal hip arthroplasty on oxidative stress in mouse liver cells.</p><p><b>METHODS</b>Eighty NIH mice were randomly divided into 4 groups and subject to intraperitoneal injection of CrO(3) at the dose of 0, 5, 10 or 20 mg/kg every other day for 16 weeks. Five mice from each group were selected every 4 weeks for determining the content of chromium (VI) in the whole blood and the levels of reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione reductase (GR) activity, and glutamate cysteine ligase (GCL) expression in the liver cells. The ultrastructural changes of the liver cells were also observed using transmission electron microscopy.</p><p><b>RESULTS</b>Exposure to 5 and 10 mg/kg CrO(3) caused significantly increased blood chromium concentration and ROS level, which reached the peak level at 8 weeks and became stabilized, whereas at the dose of 20 mg/kg, CrO(3) exposure resulted in progressive, time-dependent increase of blood chromium concentration and ROS level. MDA showed no significant changes in the 4 groups. With the prolongation of the exposure time, GSH content and GR activity were decreased in these groups. In 5 and 10 mg/kg CrO(3) groups, GCL expression increased at each time point of measurement, but in 20 mg/kg group, GCL expression decreased gradually with a prolonged exposure. Transmission electron microscopy revealed apoptotic changes of the liver cells in 20 mg/kg group.</p><p><b>CONCLUSION</b>The slow accumulation of trace chromium (VI) after metal-on-metal hip arthroplasty may cause oxidative stress and changes in the oxidative stress system in the liver cells.</p>