OBJECTIVETo explore the changes of protein expression of mitochondrial fission gene dynamin-related 1(Drp 1) in the cortical neurons of rats with chronic fluorosis.

METHODSA total of 120 one-month-old SD rats (each weighing approximately 100-120 g at the beginning of the experiment) were randomly divided into three groups, and fed with the different doses of fluoride containing in drinking water (untreated control containing 0 mg/L fluoride, and low-fluoride & high-fluoride supplemented with 10 and 50 mg/L fluoride,respectively). After 3 or 6 months exposure, 20 rats from each group were killed. Then the protein expression of mitochondrial fission gene, Drp1, was detected by immunohistochemistry and western-blotting method.

RESULTSDental fluorosis and urinary fluorosis were obviously found in the rats exposed to fluoride. At the experiment period of 3 months, the numbers of positive cells of Drp1 detected by immunohistochemistry changed. Compared with the control group (36.3 ± 5.8), the changes in low-fluoride group (34.7 ± 4.1) showed no significant difference (t = 1.5, P > 0.05),but the increase in high-fluoride group (45.0 ± 4.7) had statistical significance (t = 8.8, P < 0.05). The western-blotting method had consistent results. Compared with the control group (0.59 ± 0.03), a significant increase of the average topical density in low- fluoride (0.62 ± 0.03) and high-fluoride (0.71 ± 0.02) groups were found (t = 0.02,0.11, P < 0.05). At the experiment period of 6 months, the numbers of positive cells of Drp1 detected by immunohistochemistry significantly changed. Compared with the control group (33.2 ± 4.4), the number in low- fluoride and high-fluoride groups were separately (36.6 ± 3.8) and (39.4 ± 4.2),both increased significantly (t = 3.5,6.3, P < 0.05). Same results could be found in western-blotting method,compared with the control group (0.65 ± 0.06), the average topical density in low- fluoride (0.80 ± 0.09) and high-fluoride (0.76 ± 0.08) groups both increased significantly (t = 0.1,0.1, P < 0.05).

CONCLUSIONSTaking excessive amount of fluoride might result in the changes of expression of Drp1, and the neurons damage from the chronic fluorosis might be associated with the hyperfunction of mitochondrial fusion.