| Objective:By feeding the rats dringking the same concentration of fluoride with different concentrations of sodium selenite, we oberserve and explore the anatagonistic action of selenium. Concentration of fluoride in urine,GSH-PX activity in serum,CAT activity in serum,Hb content,dental germ ameloblasts and the differences of smad3 and shh expression are carefully obersved and recorded.Methods:Sixty clean male SD rats, weighing 80g-110g, are divided randomly into 6 groups after been feeding at the Guiyang Medical College animal laboratory for adaptation. The six groups are the control group, the fluoride group,the first fluorine and selenium group,the second fluorine and selenium group, the third fluorine and selenium group and the fourth fluorine and selenium group with 10 rats per group. Each group is caged, artificial fed, with free access to water and food. The control group is fed with normal diet and distilled water. The experimental groups are fed with distilled water conatining 45m/L fluoride (F.). The fluoride group is fed with normal diet. The frist fluorine and selenium group is fed with diet containing 1.37mg/kg of selenium. The second fluorine and selenium group is fed with diet containing 1.6mg/kg of selenium. The third fluorine and selenium group is fed with diet containing 2.3mg/kg of selenium. The fourth fluorine and selenium group is fed with diet conatining 4mg/kg of selenium. The experiment lasts two months, in which general conditions and body weight of rats is observed and recorded per week. For every two weeks,8 rats in each group is 24-hour urine collected. Rats are forbidden to drink and eat. The groups are then devided into several stages by the detal fluorosis according to the "Urinary Fluoride Ion Selective Electrode Method (WS/T30-1996) " fluoride content in urine. At the end of the first and the second month,8 rats in each group are selected to collect tail blood. Then a special kit oxidation index measurement of serum is done to measure serum glutathione peroxidase activity of catalase and the iron with high Hb cyanide method is done to measure Hb content and iron concentration. At the end of the experiment, the rats were decapitate and the part containing the mandible incisors is fixed, decalcified, and sliced. Immunohistochemistry is used to detect the expression of smad3, shh in secretory ameloblasts and image analysis software is used to conduct semi-quantitative analysis on the immunohistochemical results. All the data are subjected to the Statistical software with SPSS 17.0.Results:At the fourth week of the experiment-dental fluorosis began to appear in the fluoride group, and the dental fluorosis symptoms gradually worsened, as the time exposed to fluoride increases. By the end of the 8th week, moderate dental fluorosis appeared in the fluoride group. At the the 6th week, Fluorine and selenium group began to display dental fluorosis symptoms. At the end of the experiment, each of the Fluorine and selenium groups displayed symptoms of dental fluorosis lighter than that of the fluoride group. The difference between the third fluorine and selenium group, and the rest of the fluorine and selenium groups is statistically significant (P<0.05). The symptoms of dental fluorosis of the fourth group of fluorine and selenium were slightly worse than that of the fluoride group. At the end of the 8 week, the body weight of rats in each group increased, but the the growth rate in body weight of the experimental rats was lower than that of the experimental group (p<0.05). The Third fluorine and selenium group and fluoride group has a higher growth rate compared with the rest of the fluorine and selenium groups. The difference is statistically significant (p<0.05) Fluoride concentration in urine of rats increased as the exposure time to fluoride increases. Despite the control group, the urinary fluoride concentrations in the experimental group were higher than that of the control group in both the first and the second of the experimental month, group (p<0.05). The urinary fluoride concentration of fluoride group was higher than the first, second and the third fluorine and selenium group while the urinary fluoride concentration of the third fluorine and selenium group was higher than that of the first and the second group (P<0.05). Since the fourth week, the fluoride concentration in urine of the fourth fluorine and selenium group began to drop slightly and thus was less than that of the fluorine group. The results of oxidation-specific test kit indicators of serum GSH-PX and CAT activity showed that during the first and the second month of the experiment, the GSH-PX activity of the experimental group was lower than those in the serum of the control group (P<0.05). The GSH-PX activity of the second fluorine and selenium group was higher than that of the fluorine group, and the difference between them is statistically significant (p<0.05).The difference between the first and the second moth of the experiment is not statistically significant. (p>0.05). CAT activity of the serum in each group displayed no significant difference between them. The Hb in each group showed no significant change as well (p>0.05). As for the Immunohistochemistry results, the expression of ameloblasts smad3 and shh is positive in the control group and, and the expression in the fluoride group was significantly reduced, compared with the control group (p<0.01). The Fluorine and selenium groups'smad3 and shh expression was stronger than that of the fluoride groups , especially that the third group displayed a difference statistically significant compared with the fluoride group (P<0.05).Conclusion:1.Excess fluoride can inhibit the activity of antioxidant enzymes in rats, causing oxidative damage. Selenium can reduce free radical metabolic disorder, thus has a certain antagonism effect on the fluoride.2.Selenium only shows antagonism effect on the fluoride within a certain range of concentration, so that excessive selenium could have a synergistic effect of fluoride.3.Selenium can promote dental germ development because it can renew the expression of the signal transduction factor smad3 and shh, which control the dental germ development. The mechanism of the antagonize effect of selenium with fluorosis may be related to the expression of the signal transduction factor smad3, shh which control the dental germ development.4.Selenium can reduce the toxicity of fluoride and the symptoms of dental fluorosis. The antagonistic actions of selenium with different concentrations on fluorosis have different antagonistic effects. The optimal concentration is 2.3mg/kg selenium. |
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