Objective To investigate the protective effects of quercetin on cadmium-induced cytotoxicity in primary cultures of rat proximal tubular(rPT)cells.Methods Primary cultures of rPT cells undergoing exponential growth were incubated with 1.0 μg/mL quercetin and/or cadmium(2.5,5.0 μmol/L),in a serum-free medium at 37 ℃ at different time intervals.Commercial kits were used and flow cytometric analyses were performed on rPT cell cultures to assay apoptosis and oxidative stress.Results Exposure of rPT cells to cadmium acetate(2.5,5.0 μmol/L)induced a decrease in cell viability,caused an increase in apoptotic rate and apoptotic morphological changes.Simultaneously,elevation of intracellular reactive oxygen species,malondialdehyde and calcium levels,depletion of mitochondrial membrane potential and intracellular glutathione,and inhibition of Na +,K +-ATPase,Ca 2+-ATPase,glutathione peroxidase(GSH-Px),catalase(CAT),and superoxide dismutase(SOD)activities were revealed during the cadmium exposure of rPT cells.However,simultaneous supplementation with 1 μg/mL quercetin protected rPT cells against cadmium-induced cytotoxicity through inhibiting apoptosis,attenuating lipid peroxidation,renewing mitochondrial function and elevating the intracellular antioxidants(non-enzymatic and enzymic)levels.Conclusion The present study has suggested that quercetin,as a widely distributed dietary antioxidant,contributes potentially to prevent cadmium-induced cytotoxicity in rPT cells. Objective To investigate the protective effects of quercetin on cadmium-induced cytotoxicity in primary cultures of rat proximal tubular (rPT) cells. Methods Primary cultures of rPT cells undergoing exponential growth were incubated with 1.0 μg / mL quercetin and / or cadmium (2.5, 5.0 μmol / L) in a serum-free medium at 37 ° C at different time intervals. Commercial kits were used and flow cytometric analyzes were performed on rPT cell cultures to assay apoptosis and oxidative stress. Results Exposure of rPT cells to cadmium acetate (2.5 , 5.0 μmol / L) induced a decrease in cell viability, caused an increase in apoptotic rate and apoptotic morphological changes. Simultaneously, elevation of intracellular reactive oxygen species, malondialdehyde and calcium levels, depletion of mitochondrial membrane potential and intracellular glutathione, and inhibition of Na +, K + -ATPase, Ca 2 + -ATPase, glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD) activities were revealed during the cadmium exp osure of rPT cells. Evenly supplemented with 1 μg / mL quercetin protected rPT cells against cadmium-induced cytotoxicity through inhibiting apoptosis, attenuating lipid peroxidation, renewing mitochondrial function and elevating the intracellular antioxidants (non-enzymatic and enzymic) levels. Confluence present study has suggested that quercetin, as a widely distributed dietary antioxidant, contributes potentially to prevent cadmium-induced cytotoxicity in rPT cells.