Effect of subchronic fluoride intoxication on inducible nitric oxide synthase expression in rat bone tissue

Abstract

Objective To observe the expressions of inducible nitric oxide synthase(iNOS) in the progress of rat subchronic fluorosis,and analyse the mechanism of nitric oxide(NO) free radical injnry in bone.Methods Male wistar rats were divided randomly by body weight into two groups.i.e.sodium fluoride group and control group.Sodium fluoride group was given drinking water with 150 mg/L sodium fluoride,and control group was given tap water only.The animals were bred for 24 weeks.Every four weeks some rats were killed.The contents of serum and bone fluoride were examined and analyzed.The levels of serum NO were determined by Griess Reagent.The expressions of iNOS mRNA and protein were analyzed by RT-PCR and immunohistochemistry.Results The serum NO contents significantly increased(t=9.36,P＜0.01) in NaF-treated rats after 8 weeks[(19.94±3.04)nmol/L],but significantly decreased(t=10.47,4.46,P＜0.01) after 20 weeks[(11.55±3.54)nmol/L]and 24 weeks[(20.83±2.49)nmol/L],compared with control group[(9.11±1.21,31.13±3.93,33.10±7.37)nmol/L].The expression of iNOS mRNA significantly increased(t=13.09,4.82,14.23,4.64,7.82,5.29,P＜0.01)in rats treated with sodium fluoride[(1.87±0.11),(1.87±0.78),(1.90±0.29),(1.93±0.67),(1.88±0.38),(1.84±0.03)],compared with control group[(0.41±0.25),(0.30±0.17),(0.18±0.06),(0.63±0.15),(0.66±0.04),(0.65±0.55)],and these proteins mainly appeared in hyperplasie zone and hypertrophic zone cells of epiphyseal plate,cartilages,articular cartilage cells,osteoblasts and ligament cells.Conclusions High dose fluoride might persistentlv induce the expressions of iNOS and catalyze synthesis of NO,then regulates osteoblast and osteoclast activitv and finally influences bone turnover. Key words: Fluoride poisoning; Bone and bones; Nitric oxide synthase