Abstract: Objective To investigate the effect of high-salt diet on blood pressure,renal morphology and osteopontin (OPN) expression in Sprague-Dawley rat with AngⅡ-induced renal injury. Methods Thirty-six male SD rats aged 12 weeks receiving normal salt diet were rolled in the study,and received AngⅡ(100 ng·kg^-1·min^-1) for two weeks using subcutaneous minipump.Rats were then fed high sodium (n=18,4% NaCl) or normal sodium (n=18,0.6% NaCl) diet from third week respectively and lasted for 12 weeks.Eighteen rats in the control were sham-operated and fed normal sodium diet.Tail systolic blood pressure (SBP) was determined every two weeks.Expressions of TGF-β1、OPN mRNA and its protein in SD rat kidney were measured with quantitative RT-PCR and immunohistochemistry respectively at the end of Ang II infusion and at the end of the experiment.Renal ultrastructure was observed by electronmicroscopye. Results SBP of the rats received AngII increased significantly compared with controls (P?0.05).SBP returned to normal after AngⅡ infusion stopped.No significant difference existed in blood pressure between rats fed high salt diet and normal salt diet in the period of 12 weeks (P<0.05).Expressions of TGF-β1,OPN mRNA and its protein in the kidney of the rats fed with high salt diet were up-regulated at the end of AngⅡ infusion (P>0.05) and at the end of the 12th week compared with the rats fed normal salt diet and controls (P<0.01).The kidney was damaged by AngⅡ,which was further aggravated by the infusion of high salt diet. Conclusions High salt diet could aggravate the renal injury of the rats with AngⅡ-induced renal injury that may be independent of blood pressure change.Expressions of the TGF-β1,OPN mRNA and its protein were up-regulated after renal injury.