Toxic Effect And Protective Effect Of Different Concentrations Of Selenium On Yeast Cells

As a kind of metal element,selenium plays an important role in the body.Human industrial production activities will produce some selenium compounds,making them a potential environmental pollutant,and then causing damage to the ecological environment and species.There is a narrow range of safe use of selenium between the optimal concentration and the toxic concentration.Dietary selenium deficiency is associated with a variety of endemic diseases.It can cause diseases such as Keshan disease,osteoarthritis,and abnormal myocardial function.When animals take high doses of selenium,respiratory distress,exercise disorders,abdominal pain,diarrhea,and even death may occur.Excessive intake of selenium not only causes severe toxicity to animals and humans,but also has a significant accumulation effect.Therefore,Selenium toxicity should be given great attention.However,the molecular mechanism of the toxic effects of selenium is still unknown.Yeast is the first eukaryote to complete whole genome sequencing.It has the characteristics of easy cultivation,short growth cycle,simple genetic background,and strong operability.It has become a model organism for the study of eukaryote cytology and has been widely used.Applied to studies such as cell division and death.The results obtained with yeast cells were more than 90%consistent with higher animal and plant cells.In this thesis,yeast cells were used as experimental materials.Spectrophotometry and methylene blue staining were used to study the toxic effects of selenium and its effects on chromium toxicity.The main experimental results are as follows:1.0.5-10 mmol/L Se had a certain inhibitory effect on the growth of yeast cells.With the increase of selenium concentration,the inhibitory effect on yeast cell growth and division was enhanced,and 10 mmol/L Se almost completely inhibited the yeast cells.Growing and splitting.High concentration of selenium could induce the death of yeast cells,and the cell death rate increased with the prolongation of the action time and the increase of treatment concentration,showing a certain time and concentration effect.When cells die,cyt c released into the cytoplasm after mitochondrial membrane damage.The results of the study indicate that certain concentrations of selenium can induce yeast cell death,which is associated with mitochondrial damage.2.Antioxidant?0.5 mmol/L AsA?,Ca²⁺interference agent(0.5 mmol/L Ca²⁺chelating agent EGTA)and NO?1 mmol/L NO synthesis inhibitor NaN₃and 0.5 mmol/L Na₂WO₄·2 H₂O?were respectively high After treatment with selenium?3 mmol/L and 5 mmol/L?for 6 h,the cell death rate decreased,indicating that the high concentration of selenium-induced yeast cell death was related to intracellular levels of ROS,Ca²⁺,and NO.3.The concentration of 3 mmol/L Cr⁶⁺significantly inhibited the growth of yeast cells and had a certain time effect.ROS fluorescent indicator DCFH-DA,Ca²⁺fluorescent indicator Fluo-3 AM,NO fluorescent indicator DAF-FM DA were used to detect intracellular ROS,Ca²⁺and NO levels.Chromium(Cr⁶⁺)was found to induce yeast intracellular ROS,Ca²⁺,NO levels increased significantly.The yeast cells were treated with 1 mmol/L Se and 3 mmol/L Cr⁶⁺.The mortality of the cells was significantly lower than that of the chromium(Cr⁶⁺)-treated group.The MDA content and antioxidant enzyme activity of the yeast cells were determined by combined treatment.The results showed that after 9 h treatment with chromium(Cr⁶⁺),the MDA content in the yeast cells was increased compared with the control group,and the superoxide in the yeast cells was increased.The activity of dismutase?SOD?,catalase?CAT?and peroxidase?POD?increased.It was shown that chromium(Cr⁶⁺)can cause oxidative damage of yeast cells and change the activity of intracellular antioxidant enzymes.