骨桥蛋白在低钙和燃煤污染型氟中毒大鼠肾组织中的表达

目的 观察骨桥蛋白(OPN)在低钙和氟中毒大鼠肾组织中的表达,探讨OPN与氟中毒肾损害的关系.方法 1月龄Wistar大鼠48只,雌雄各半,体质量80～100 g.按2×2析因设计将大鼠按质量随机分为4组:对照组、高氟组、低钙组、低钙高氟组,每组12只,雌雄各半.采用合成饲料喂养,高氟组和低钙高氟组饲料中的玉米来自燃煤污染型氟中毒病区,含氟量为100 mg/kg,对照组和低钙组饲料中的玉米来自于非病区,含氟量为5 mg/kg.喂养16周后处死大鼠,观察各组大鼠牙齿变化,计算大鼠氟斑牙检出率.取大鼠肾脏,采用RT-PCR技术及免疫组化技术检测大鼠肾脏OPN蛋白和OPN mRNA表达.结果 对照组和低钙组牙齿生长良好,高氟组、低钙高氟组大鼠均出现明显的氟斑牙,氟斑牙检出率为100%.免疫组化结果表明,OPN主要定位于肾组织的肾小管上皮细胞中.对照组和低钙组肾组织OPN阳性细胞淡染、散在分布,高氟组与低钙高氟组OPN阳性细胞着色较深,广泛分布在肾小管上皮细胞中.OPN蛋白表达显示,高氟组(168.64±13.21)和低钙高氟组(169.26±8.92)高于对照组(145.78±10.26,P均<0.01)和低钙组(149.60±16.84,P均<0.01);OPN mRNA表达显示,高氟组(1.89±0.37)和低钙高氟组(1.94±0.22)高于对照组(1.32±0.26,P均<0.05)和低钙组(1.30±0.18,P均<0.05).高氟影响OPN蛋白和OPN mRNA表达(F=13.821、4.24,P均<0.05),低钙不影响OPN蛋白和OPN mRNA表达(F=2.164、0.58,P均>0.05),但高氟和低钙联合作用时,二者对OPN蛋白和OPN mRNA表达有交互作用(F=6.257、4.32,P均<0.05).结论 过量氟可促使大鼠肾组织的OPN表达增加,提示OPN与氟中毒肾损害程度密切相关,可考虑作为一种氟中毒肾损害的标志,并且,高氟与低钙同时存在时,大鼠肾损害会进一步加重,提示低钙是氟化物损害肾脏的重要环节.

Expression of osteopontin in renal tissue of rats with endemic fluorosis caused by exposure to coal burning and with low calcium

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.