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BACKGROUND: Parkinson disease is neurodegenerative disorders, characterized by a progressive and selective degeneration of nigrostriatal dopaminergic pathway. Its main clinical symptoms include bradykinesia, rigidity, rest tremor and disturbances in balance. Levodopa (L-DOPA) is the gold standard for the symptomatic treat ment of Parkinson disease, but L-DOPA is toxic to dopaminergic neurons and the chronic administration of L-DOPA often causes the side effects of motor such as on-off , etc., and its mechanism still has not been completely clarified.OBJECTIVE: To observe the changes of the content of glutathione (GSH), activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and content of malondialdehyde (MDA) in glia-containing mesencephalic culture fluid after L-DOPA of different concentrations were added.DESIGN: A comparative observation.SETTINGS: Department of Neurology, Affiliated Hospital of Taishan Medical University; Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology. MATERIALS: The experiment was carried out in the Basic Research Institute, Taishan Medical University from December 2003 to September 2004. Ten postnatal newb SD rats (within 2 days) were selected, either male or female. Fetal bovine serum (DMEM/F12) was from Gibco Company; L-DOPA and glial fibrillary acidic protein (GFAP) from Sigma Company. Kits for determination of GSH, GSH-Px, SOD and MDA were purchased from Nanjing Jiancheng Bioengineering Research Institute.METHODS : Glia-containing mesencephalic culture fluid were placed in 24-well culture plate, and L-DOPA of 50, 100 and 500 μmol/L was added to each group, the blank control group was also set. The glia-containing mesencephalic culture fluid selected at 4, 24, 48 and 72 hours respectively to determine the GSH content with colorimetric quantitative technique, GSH-Px activity with colorimetric method, SOD activity with xanthine oxidase method and MDA content with thiol-barbituric acid method.MAIN OUTCOME MEASURES: GSH and MDA contents, GSH-Px and SOD activities in the glia-containing mesencephalic culture fluid at 4, 24, 48 and 72 hours after L-DOPA of different concentrations were added. RESULTS: In the glia-containing mesencephalic culture fluid after 100 μmol/L L-DOPA was added for 24, 48 and 72 hours, the GSH contents were lower than those in the blank control group [(174.14±39.28), (161.55± 40.79), (144.97±57.59) mg/L; (220.66±32.61), (221.10±32.98), (220.43±31.98) mg/L, P ＜ 0.05]; The GSH-Px activities were lower than those in the blank control group [(4.03±1.05), (3.99±1.12), (3.47±1.00) μmol/L; (5.45±1.14), (5.69±1.21), (5.49±1.28) μmol/L, P ＜ 0.05]; The SOD activities were also lower than those in the blank control group [(42.02±5.08), (39.38±5.34), (38.87±5.75) kNU/L; (51.35±8.87), (51.78±8.96), (50.99± 9.09) kNU/L, P ＜ 0.05]; Whereas the MDA contents were higher than those in the blank control group [(3.51 ± 1.05), (3.99±1.03), (4.45±1.58) μmol/L; (2.09±1.13), (2.18±1.29), (2.01±1.05) μ mol/L, P＜ 0.05]. In the glia-containing mesencephalic culture fluid after 100 μmol/L L-DOPA was added for 4, 24, 48 and 72 hours, the GSH contents were (172.27±26.07), 140.15±61.44), (137.30±50.87), (121.09±66.07) mg/L, the GSH-Px activities were (3.89±1.20), (3.56±1.23), (3.38±1.18), (3.01±1.09) μmol/L, the SOD activities were (38.18±6.75),(35.23±7.85), (4.59±1.24), (31.42±7.01) kNU/L, which were all lower than those in the blank control group (P ＜ 0.05-0.01); The MDA contents were (3.65±0.86), (3.87±1.14), (4.59±1.24), (4.79±1.32) μmol/L, which were higher than those in the blank control group (P ＜ 0.05-0.01). In the glia-containing mesencephalic culture fluid added by 50 μmol/L L-DOPA, the GSH and MDA contents, GSH-Px and SOD activities at each time point were all close to those in the blank control group (P＞ 0.05).CONCLUSTON: L-DOPA of certain concentration can destroy the dynamical balance of free radicals in glia-containing mesencephalic culture fluid, and accelerate the degeneration of neurons, which are in concentrationand time-dependent manners.