Abstract: OBJECTIVE: To investigate the effect of olaquindox on the antioxidant system in human hepatoma G2(HepG2) cells. METHODS: HepG2 cells were treated with 0, 200, 400 and 800 μg/ml olaquindox in 24 h. The activities of superoxide dismutase(SOD) and catalase(CAT), the level of malondialdehyde(MDA), the activities of glutathione (GSH) and glutathione peroxidase (GSH_PX), Na＋K＋_ATPase and Ca2＋Mg2＋－ATPase were measured. SOD or CAT, and the combination of SOD＋CAT were incubated for 3 h with olaquindox_treated HepG2 cells. The levels of reactive oxygen species (ROS) were evaluated by 2, 7_dichlorodihydrofluorescein diacetate(DCFDA). RESULTS: Olaquindox decreased the levels of T_ATPase, Na＋K＋－ATPase and Ca2＋Mg2＋－ATPase, SOD,GSH ,GSH_PX, in HepG2 cells(P<0.05 or P<0.01), with a dose_response relationship. After HepG2 cells were treated with olaquindox, the activity of CAT was decreased when compared with the control(P<0.01). Olaquindox led to a dose_dependent increase in the level of MDA(P<0.05 or P<0.01). While HepG2 cells were treated with olaquindox (800 μg/ml), CAT,SOD and SOD＋CAT reduced ROS about 80％ ,40％and 95％, respectively(P<0.01). CONCLUSION: Olaquindox disrupted the antioxidant system in HepG2 cells. Our results indicated that olaquindox_induced HepG2 cells predominantly generated H2O2, which could be scavenged by CAT.

Key words: olaquindox, superoxide dismutase, catalase, glutathione, ATPase, reactive oxygen species