This study was undertaken to determine whether Salviae-radix (SVR) extraction prevents the oxidant-induced cell injury and thereby exerts protective effect against oxidant-induced inhibition of tetraethylammonium uptake (TEA) in renal corticaJ sices. SVR (5%) attenuated $H_2O_2-induced$ inhibition of TEA uptake. $H_2O_2$ increased LDH release and lipid peroxidation in a dose-dependent manner. These changes were prevented by SVR extraction. The protective effect of SVR on LDH release was dose-dependent over the concentration range of 0.1-0.5%, and that on lipid peroxidation over the concentration ranges of 0.05-2%. SVR significantly prevented Hg-induced lipid peroxidation. SVR extraction (0.5%) increased cellular GSH content in normal and $H_2O_2-treated$ tissues. When slices were treated with 100 mM $H_2O_2$, catalase activity was decreased, which was prevented by 0.5% SVR extraction. The activity of glutathione peroxidase but not superoxide dismutase was significantly increased by 0.5% SVR extraction in $H_2O_2-treated$ tissuces. These results suggest that SVR has an antioxidant action and thereby exerts benefical effect against oxidant-induced impairment of membrane transport function. This effect of SVR is attributed to an increase in endogenous antioxidants such as GSH, catalase and glutathione peroxidase.