Abstract: Abstract Objective：To investigate the effects of exogenous hydrogen peroxide (H2O2) expose on mitochondrial superoxide production and mitochondrial membrane potential（Δψ）changes in Fisher rat thyroid cell line (FRTL) cells. Methods：Following exposed in 1 mmol/L H2O2 for 10 min, 30 min and 24 h respectively mitochondrial superoxide production in FRTL cells were measured by living cell imaging and flow cytometry using MitoSOX. After exposed in 1 mmol/L H2O2 for 30 min and 24h mitochondrial membrane potential (Δψ) was assayed by spectrofluorimeter and fluorescent microscopy using rhodamine 123(rh123). Cell viability was detected by MTT colorimetric method. Morphological changes were observed by invert microscope. Apoptosis assay was performed by acridine orange staining. Results：Quantitative measurements of the mean intensities of MitoSOX from the samples demonstrated significantly increased with 1mmol/L H2O2 following 10 min,30 min and 24 h treatment. Fluorescence intensity of rh123 in FRTL cells and optical density of MTT colorimetric method markedly decreased with 1mmol/L H2O2 following 30 min and 24 h treatment（p＜0.01）. Under light microscope and fluorescence microscope after acridine orange staining, the characteristic morphological features of programmed cell death, picknosis, karyorrhexis, and cell shrinkage were observed. Conclusion：Acute and chronic exogenous H2O2 expose cause oxide stress in FRTL cells which result in mitochondrial superoxide production increase , Δψ decline, cell necrosis and apoptosis .

Key words: hydrogen peroxide, FRTL cells, mitochondrion, superoxide, mitochondrial membrane potential