Abstract: Objective To investigate the effect of high-salt diet on the expression of osteopontin (OPN) mRNA and its protein in Sperague-Dawley rat kidney.Methods Forty-eight male SD rats aged 10 weeks receiving normal salt diet were enrolled in study, and were divided into two groups and fed with high salt diet (4%NaCl) or normal salt diet (0.6%NaCl) for 12 weeks respectively, with 24 rats in each group. Tail systolic blood pressure and bodyweight were measured in all rats every week. At the end of 4th, 8th and 12th week, 6 rats in each group were sacrificed for detection of the expression of OPN mRNA and its protein in the kidney with quantitatine real-time (QRT)-PCR and immunohistochemistry, respectively.Results No significant difference was found in blood pressure, bodyweight and kidney weight/bodyweight between high-salt diet group and normal salt diet group (P>0.05). The expression of OPN mRNA (0.27±0.16 vs 0.15±0.13, P<0.05) and its protein (0.78±0.15 vs 0.61±0.11, P<0.01) in SD rat kidney with high-salt diet were up-regulated at the end of 12th week compared with the rats with normal salt diet.Conclusions High-salt diet increase the expression of OPN mRNA and its protein in SD rat kidney. Renal injury induced by high salt intake might be independent of blood pressure change.