Abstract: 【Abstract】 Objective To explore the role of heparanase in the pathogenesis of respiratory syncytial virus (RSV) nephropathy in rats model. Methods Twenty 150-200 g Sprague-Dawley (SD) rats (n=5 per group) were inoculated with 6×10 ⁶ PFU RSV and sacrificed on days 4,8,14 and 28 postinoculation (RSV ₄,RSV₈,RSV₁₄ and RSV₂₈). Five SD rats inoculated with Dulbecco’s minimum essential medium were served as normal control. The expression levels of heparanase protein and mRNA in the rat renal tissue of each group were determined by immunohistochemical staining and real-time quantitative RT-PCR respectively. The proteinurina was also measured and then the relationship between the expression level of heparanase and the 24-hour urinary protein was studied. Results The rats with RSV nephropathy exhibited higher proteinuria in comparison with normal rats, and the 24-hour urinary protein level was significantly different between each RSV nephropathy group (RSV₁₄＞RSV₈＞RSV₂₈＞RSV ₄, P <0.05）. Compared with normal control, the rats with RSV nephropathy showed up-regulated expression of heparanase protein in glomeruli. The expression levels of heparanase protein in RSV₈and RSV₁₄group were higher than those in RSV ₄ and RSV₂₈group （P <0.05）.There was a linear positive correlation between the expression level of glomerular heparanase protein and the quantity of 24-hour urinary protein （r=0.783,P <0.05）.Compared with normal control group, the expression levels of heparanase mRNA in the kidney from RSV ₄, RSV₈, RSV₁₄ and RSV₂₈ group were elevated （RSV₁₄＞RSV₈＞RSV ₄₂₈, P<0.05）.There was a linear positive correlation between the expression level of renal heparanase mRNA and the quantity of 24-hour urinary protein （r=0.725,P <0.05）. Conclusion The increased expression of heparanase in kidney may be important to the loss of glomerular negative charge in glomerular basement membrane which is involved in the pathogenesis of RSV nephropathy in rats.