Abstract: AIM:To investigate the expression and the effects of telmisartan on the matrix metalloproteinase-9(MMP-9)and the tissue inhibitor of metalloproteinase-2(TIMP-2)of carotid arterial media in spontaneously hypertensive rats(SHRs).METHODS:12 week-old male SHRs were randomized to untreated SHR group (SHR), telmisartan high dose group (TelH)and telmisartan low dose group(TelL)(n=10 for each).Age and sex matched Wistar Kyoto rats (WKY)were served as control group (n=10).After 18 weeks intervention, systolic blood pressure (SBP)of rats and area of collagen fiber percentage were measured.MMP-9 and TIMP-2 expression levels in the carotid arterial media were evaluated with immunohistochemistry staining.RESULTS:After 2 weeks, the SBP level in TelH group was significantly decreased compared to SHR group (P<0.01).And the SBP lowering effect in TelH group was kept during the experiment.However, there was no significant difference between SHR group and TelL group(P>0.05).The area of collagen percentage in carotid arterial media of SHR group were higher than that in WKY group(P<0.01).In TelH and TelL group the areas were lower than that in SHR group respectively (P<0.05 for each).The integrated optical density(OD of MMP-9 in the carotid arterial media in SHR group was markedly lower than that in WKY group(P<0.01).The OD in TelH and TelL group was higher than that of SHR group respectively (P<0.05 for each).The OD of TIMP-2 in the carotid arterial media in SHR group was markedly higher than that in WKY group(P<0.01). In TelH and TelL group it was markedly lower than that of SHR group respectively(P<0.05 for each).CONCLUSION:MMP-9 expression level decreased but TIMP-2 level increased in carotid arterial media of SHRs.Telmisartan could attenuate carotid arteries fibrosis through decreasing SBP, upregulating MMP-9 and downregulating TIMP-2 expression levels on carotid arteries of SHRs.

Key words: spontaneously hypertensive rat, carotid artery, MMP-9, TIMP-2, telmisartan