The Study Of Peroxide Injury Of Iodide Excess On FRTL Cells

To investigate effects of excessive potassium iodide (KI) on mitochondrial superoxide production, cell vitality and cell apoptosis on Fisher rat thyroid cell line (FRTL) and reveal the development process of peroxide damage caused by iodide excess. To investigate whether iodide-induced peroxide damage can be impeded by pharmacological means known as thyrotropin (TSH) or antithyroid drug propylthiouracil (PTU).1. Treating FRTL cells with different concentration (10-7mol/L～10-2mol/L) KI for 30min,24h, changes of cell vitality were evaluated by methyl thiazolyl tetrazolium (MTT) colorimetry. Potassium chloride (KCl) of corresponding concentration was used as osmotic control.2. After treatment with 10-4mol/L or 10-2mol/L KI for 2h,4h,24h, changes of superoxide formation and percent of dead cells were assayed by flow cytometry using MitoSOX and propidium iodide (PI) respectively. Cytochrome c release from mitochondria to cytoplasm was detected by enzyme linked immunosorbent assay (ELISA) and immuncytochemity. Lactate dehydrogenase (LDH) activity in culture fluid was evaluated by LDH kit. DNA fragmentation was measured by agarose electrophoresis. Ultrastructural alterations were observed by transmission electron microscope.3. After treatment with 10-4mol/L KI with or without 10U/L TSH for 24h, changes of mitochondrial superoxide production and cell vitality were detected.4. After treatment with 10-4mol/L KI with or without 300μmol/L PTU for 2h, 24h, mitochondrial superoxide formation and cells vitality were measured.1. Treatment for 30min no detectable effects on cell vitality were found in 10-7mol/L～10-2mol/L KI groups(p>0.05). Treatment for 24h, cell vitality in 10-5mol/L～10-2mol/L KI groups was significantly decreased compared to control group (p<0.05). Treatment for 30min,24h respectively no significant changes of cell vitality were found in 10-7mol/L～10-2mol/LKCl groups (p>0.05).2. Mitochondrial superoxide production in FRTL cells was increased at 2h,4h and 24h, especially at 2h. Cyt c was released from mitochondria to cytoplasm at 2h, 4h,24h (p<0.05, p<0.01). LDH activity in culture medium was significantly increased at 4h,24h (p<0.01) and death cell percent was increased with treatment time. DNA ladder was present at 24h. Under transmission electron microscope swelling mitochondria were observed at 2h, damage of cell membrane and mitochondrial membrane, endoplasmic reticulum vesiculation and accumulation of lipofuscin in secondary lysosomes were present at 4h as well as apoptotic body was observed at 24h.3. Compared with KI group, mitochondrial surperoxide prodiction was pronouncedly decreased and cell vitality was significantly increased in KI+TSH group (p<0.05).4. Compared with KI group, mitochondrial superoxide formation was pronouncedly decreased and cell vitality was increased in KI+PTU group (p<0.01).1. Effects of KI on vitality of FRTL cells were concentration dependent.2. Iodide excess induced peroxide injury on FRTL cells in a time-effect manner. At 2h mitochondrial superoxide formation was increased and cyt c was released from mitochondria to cytoplasm. At 4h cell membrane and mitochondrial membrane were damaged. At 24h cell damage was exacerbated and cell apoptosis appeared.3. Combining with 10U/L TSH may attenuate peroxide injury on FRTL cells caused by iodide excess.4. Combining with 300μmol/L PTU may attenuate peroxide damage on FRTL cells caused by iodide excess.