RESUMO
Objective To investigate the effects of fluoride exposure dose and exposure time on the expression of 5-methylcytosine (5-mC) in blood,liver,kidney and brain of rats;and to understand whether there is a difference in the effects of fluoride on DNA methylation levels in different tissues.Methods Eighty three-week old SPF male Wistar rats were randomly divided into four groups according to body weight [(82.34 ± 10.60) g],with 20 rats in each group.The rats of control group drank distilled water and the fluoride group's drank distilled water containing 25,50 and 100 mg/L of F ion,respectively.Rats were sacrificed after fed for 1 month and 3 months (n =10),and peripheral blood and tissue samples were collected.The incidence of dental fluorosis was observed in rats.Bone and urine fluoride content was detected by ion selective electrode method.The content of 5-mC in blood,liver,kidney and brain was detected by enzyme-linked immunosorbent assay (ELISA).The independent and interactive effects of fluoride exposure dose and exposure time on 5-mC in rat peripheral blood and different tissues were analyzed by factorial design anova.Results After feeding for 1 month and 3 months,all rats in the fluoride group had dental fluorosis with different severities,while none dental fluorosis was found in the control groups.Fluoride exposure dose and exposure time had a main effect on bone fluoride contents [1 month:(324.985 + 127.094),(846.148 ± 331.861),(1 886.601 + 250.140),(2 420.971 + 135.883) mg/kg;3 months:(417.591 ± 88.324),(1 582.243 ± 347.975),(2 163.519 ± 614.932),(2 755.434 ± 265.370)mg/kg;F =96.692,13.077,P ＜ 0.01],respectively,but there was no interaction effect (F =2.013,P ＞ 0.05);fluoride exposure dose had a main effect on urinary fluoride contents (F =62.358,P ＜ 0.01),the exposure time had no effect on it (F =0.862,P ＞ 0.05),and there was no interaction effect (F =0.081,P ＞ 0.05).Fluoride exposure dose had a main effect on the 5-mC content in the blood (F =8.446,P ＜ 0.01),the exposure time had no effect on it (F =0.095,P ＞0.05),and there had an interaction effect (F =4.676,P ＜ 0.01).Fluoride exposure dose and exposure time had a main effect on the 5-mC content in the liver,respectively (F =4.737,7.064,P ＜ 0.01 or ＜ 0.05),and an interaction effect was exist (F =8.302,P ＜ 0.01).Fluoride exposure time had a main effect on the 5-mC content in the kidney (F =6.340,P ＜ 0.05),the exposure dose had no effect on it (F =0.140,P ＞ 0.05),and there was no interaction effect (F =1.269,P ＞ 0.05).Fluoride exposure dose and exposure time had no effect on 5-mC content in the brain (F =0.633,2.065,P ＞ 0.05).Conclusion Fluoride exposure dose and exposure time have the different effect on the levels of 5-mC in blood,liver,kidney and brain,suggesting that there may be differences in the effects of fluoride on DNA methylation levels in different tissues.
RESUMO
Objective To investigate the effects of fluoride on protein oxidative damage in rat plasma by measuring oxidative stress levels,advanced glycation end products (AGEs) and advanced oxidation protein products (AOPP).Methods Eighty SPF male 3-week-old Wistar rats weighing (82.34 ± 10.60) g were randomly divided into 4 groups,20 rats in each group.The control group drank distilled water,and the fluoride groups drank distilled water with fluoride concentrations of 25,50 and 100 mg/L,respectively.Rats were allowed to eat and drink freely,and they were sacrificed at 1 month and 3 month,respectively,and samples such as urine,femur and peripheral blood were collected for experiments.Fluoride contents in urine and bone were detected by ion selective electrode method,the superoxide dismutase (SOD) activity was detected by hydroxylamine method,malondialdehyde (MDA) content was detected by thiobarbituric acid (TBA) method,and AGEs and AOPP contents were detected by enzyme linked immunosorbent assay (ELISA).Results For 1 month and 3 months,compared urinary fluoride contents (mg/L:2.088 + 0.638,9.170 ± 2.865,20.094 ± 8.186,54.866 ± 2.866;2.202 ± 1.282,9.112 ± 2.364,21.854 ±8.325,52.513 ± 16.211),and bone fluoride contents (mg/kg:324.985 ± 127.094,846.148 ± 331.861,1 886.601 ±250.140,2 420.971 ± 135.883;417.591 ± 88.324,1 582.243 ± 347.975,2 163.519 ± 614.932,2 755.434 ±265.370) in control group and fluoride concentrations of 25,50 and 100 mg/L groups,the differences were statistically significant (F =88.379,29.225;87.440,33.998,P ＜ 0.05).For 1 month and 3 months,compared SOD activity (U/ml:32.469 ± 5.674,35.931 ± 2.262,36.746 ± 3.994,38.042 ± 4.632;31.027 ± 4.147,30.777 ±4.791,34.148 ± 1.755,36.585 ± 2.860) and AGEs contents (μg/L:26.977 ± 5.285,33.303 ± 6.226,28.021 ±5.946,34.117 ± 6.706;35.681 ± 3.802,33.651 ± 7.214,28.114 ± 4.660,24.330 ± 3.581) in control group and fluoride concentrations of 25,50 and 100 mg/L groups,the differences were statistically significant (F =2.896,5.780;3.565,10.195,P ＜ 0.05).By factorial design anova,there was an interaction between the exposure concentration and exposure time of fluorine and the content of AGEs (F =8.957,P ＜ 0.01).Conclusion Excessive fluoride can affect urinary,bone fluoride contents,SOD activity,AGEs content,suggesting that excessive fluoride may regulate protein expression through direct and indirect oxidative damage pathways,which leading to fluorosis.