Objective To investigate the expressions of metalloproteinase-9 (MMP-9)in serum, brain and aorta matrix and tissue inhibitor of metalloproteinase-1(TIMP-1) in renovascular hypertensive rats (RHR),and to evaluate the association between blood pressure and levels of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1(TIMP-1).Methods Eighty healthy male SD rats were randomly divided into RHR group (n=40) and sham-operated group (n=40). Hypertension was induced by two-kidney, two-clip (2K-2C)clamps.Systolic blood pressure (SBP) was measured every 2 weeks during 12 weeks using a tail pressure meter. Stroke was confirmed by Longa's five-point scale and pathological examination. The expressions of MMP- 9 and TIMP-1 in the brain and aorta tissues were detected by Western blot and immunohistochemistry. The levels of serum MMP-9 and TIMP-1 were measured by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Results Compared with the sham-operated group, SBP stayed significantly elevated in the RHR group at 2, 4, 6, 8, 10 and 12weeks after the operation [(157±9.0) vs. (128±7.0), (176±10.0) vs. (122±6.0), (194±8.0)vs. (117±6.5), (202±12.0)vs. (124±8.0), (218±15.0) vs. (126.±8.5),and (224±20.0)vs. (129.±9.0) mm Hg, all P < 0.05]. 12 weeks after the surgery, the level of serum MMP-9 in the RHR group was kept significantly higher than that in the sham-operated group [(783.4±109.79)vs. (573.4±109.59) ng/mL, P < 0.05],and the serum TIMP-1 level was lower in the RHR group than that in the sham-operated group[(313.02±83.9) vs. (976.19±191.1) pg/mL, P < 0.05]. MMP-9 expressions were significantly higher in the brain and aorta in the RHR group than that in the sham-operated group(both P < 0.05), and TIMP-1 expressions were lower than that in the sham-operated group(both P < 0.05).The Pearson correlation analysis showed that MMP-9 levels in serum,brain and aorta were positively correlated with systolic blood pressure (r=0.557,r=0.774 and r=0.661,all P < 0.05), and TIMP-1 levels were negatively correlated with systolic blood pressure(r=-0.481,r=-0.535 and r=-0.685,all P < 0.01). Conclusions Hypertension induces increased MMP-9 and decreased TIMP-1 in serum, brain and aorta in renovascular hypertensive rats. There are consistent alterations of circulating and tissue MMP-9 and TIMP-1 levels in renovascular hypertensive rats. There is a relationship between increased blood pressure and high MMP-9 and low TIMP-1 in serum and tissues.