Expression of osteopontin in renal tissue of rats with endemic fluorosis caused by exposure to coal burning and with low calcium / 中国地方病学杂志

ABSTRACT

Objective To detect the osteopontin(OPN)expression in renal tissue of rats with fluorosis and low calcium diet,and study the role of OPN in renal injury of fluorosis.Methods Forty-eight aged 1 month Wistar rats,80-120 g,were randomly divided into 4 groups by 2×2 factorial design(the number of female and male in each group was equal)the control group,high-flluoride group,low-calcium group and low-calcium with high-fluoride group.All rats of the fluorosis groups were fed with feed containing corn exposed to coal-burning from endemic fluorosis areas with high fluoride(100 mg/kg,corn),the other two groups were fed with feed containing coru from nonendemic fluorosis areas(fluoride 5 mg/kg,corn).After 16 weeks,the rats were killed.The change of teeth was examined,and the incidence rate of dental fluorosis was calculated.The expressions of both protein and mRNA of OPN in rat renal tissue were determined by RT-PCR and immunohistochemistry after four-month experimentation.Results The growth of teeth was very well in the control group and the low-calcium group.The two high-fluoride groups showed evident dental fluorosis(100%).The results of immunohistochemistry showed that the OPN protein was localized in renal tubule cytoplasm.The OPN-positive cells from renal tissue were lightly and scatteredly stained in control and low-calcium groups.The OPN-positive cells had deeper color in high-fluoride group and low-calcium with high-fluoride group,widely distributed in the renal tubular epithelial cells.The protein expression of OPN in the two groups exposed to fluoride(168.64±13.21,169.26±8.92)was significantly higher than those of the corresponding control group(145.78±10.26,all P<0.01)and low-calcium group(149.60±16.84,all P<0.01).The mRNA expression of OPN in the two groups exposed to fluoride(1.89±0.37,1.94±0.22)was significantly higher than those of the corresponding control group(1.32±0.26,all P<0.05)and low-calcium group(1.30±0.186,P<0.05),respectively.High fluoride influenced the expression of protein and mRNA of OPN(F=13.821,4.24,all P<0.05).Low calcium did not affect the expression of protein and mRNA of OPN(F=2.164,0.58,all P>0.05).However,high fluoride and low calcium had a cross interaction on the expression of protein and mRNA of OPN(F=6.257,432,all P<0.05).Conclusions Over-dose fluoride enhances the expression of OPN.The higher expression observed in the cases exposed to high fluoride concentration is associated with serious renal injury.OPN may he a potential marker for renal injury in fluorosis.Moreover,over-dose fluoride and low calcium make the renal injury worse,indicating low calcium plays an important part in renal injury by fluoride.