Background Fluorosis is a chronic systemic disease characterized by skeletal fluorosis and dental fluorosis caused by long-term intake of excessive fluorine from air, food, and water. Endemic fluorosis is widespread throughout China, and severely threatens a large populaton. To study the mechanism of fluorosis is helpful to prevent and treat skeletal fluorosis, dental fluorosis, and other bone diseases caused by excessive intake of fluoride.
Objectve This experiment is designed to investgate the effects of different doses of sodium fluoride on osteogenic actvity markers in rats, and to provide experimental data for studying the mechanism of fluorosis.
Methods Thirty-two SD rats were randomly divided into one control group (0 mg/L) and three fluoride groups (50, 150, and 250 mg/L, respectvely). Afer six months of fluoride administraton via drinking water, urinary samples were collected within 12 h to detect urinary fluoride concentration; then the rats were executed after 10% chloral hydrate anesthesia, and cardiac blood samples were collected to detect serum fluoride concentraton; lef forelimbs were ground in liquid nitrogen, and the mRNA expressions of Col Ⅰ, Runx2, and Osx were detected by real-time quanttatve PCR; right forelimbs were ground in liquid nitrogen, and the protein expressions of Col Ⅰ, Runx2, and Osx were detected by Western blot.
Results During the fluoride administration period, the rats were in good mental status with normal dietary intake and water consumpton, and there was no signifcant difference in body weight between the exposure groups and the control group. Afer the designed six-month treatment, the urinary fluoride concentratons of the fluoride groups(9.71±2.33), (20.36±4.92), and (42.36±4.56) mg/kg were statstcally higher than that of the control group(5.69±1.59) mg/kg (P < 0.05), so were the serum fluoride concentratons(0.19±0.01), (0.23±0.01), and (0.29±0.02) mg/L vs. (0.14±0.01) mg/L (P < 0.05); as the fluoride exposure dose increased, the urinary and serum fluoride concentratons showed rising trends (r=0.89, 0.90, Ps < 0.01). Afer the treatment for six months, the mRNA expression levels of Col Ⅰ in the lowdose group (0.91±0.28), the medium-dose group (0.87±0.33), and the high-dose group (0.67±0.31) were statstcally higher than that in the control group (1.31±0.43) (P < 0.05); the mRNA expression levels of Runx2 in the low-dose group (0.81±0.33), the medium-dose group (0.78±0.18), and the high-dose group (0.57±0.25) were statstcally higher than that in the control group (1.18±0.28) (P < 0.05); as the fluoride exposure dose increased, the mRNA expression levels of Col Ⅰ and Runx2 showed decreasing trends (r=-0.56, -0.31, Ps < 0.05). Compared with the control group (1.01±0.15), the mRNA expression levels of Osx in the low-dose group (1.31±0.20) and the medium-dose group (1.49±0.41) were increased, and that in the high-dose group (0.58±0.15) was decreased (P < 0.05). Afer the treatment for six months, the protein expression levels of Col Ⅰ in the low-dose group (0.17±0.02), the medium-dose group (0.15±0.01), and the high-dose group (0.11±0.03) were statstcally lower than that in the control group (0.22±0.03) (P < 0.05); as the fluoride exposure dose increased, the protein expression level of Col Ⅰ showed a downward trend (r=-0.88, P < 0.05). Compared with the control group(0.19±0.03), (0.16±0.03), the protein expression levels of Runx2 and Osx in the low-dose group(0.30±0.04), (0.25±0.02) and the medium-dose group(0.26±0.01), (0.31±0.03) were increased, but the expression levels in the highdose group(0.12±0.02), (0.10±0.03) were decreased (P < 0.05).
Conclusion The effect of fluoride on the expressions of osteogenic actvity markers is complex. As the fluoride exposure dose increases, the Col Ⅰ protein expression level shows a downward trend; whereas, the Runx2 and Osx protein expression levels of the low- and medium-dose fluoride groups are up-regulated, and those of the high-dose fluoride group are down-regulated.
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