Objective  To study the effect of angiotensin Ⅱ type 1 receptor antagonist Irbesartan on the expressions of cyclooxygenase-2 (COX-2) in rabbit model of atherosclerosis.

    Methods  Thirty male New Zealand rabbits were randomly divided into five groups: normal control group

high cholesterol group (Group HC)

10 mg·kg

-1

·d

-1

Irbesartan group (Group S)

20 mg·kg

-1

·d

-1

Irbesartan group (Group M)

30 mg·kg

-1

·d

-1

Irbesartan group (Group H). Except the control group

the other four groups were fed with high cholesterol diet to induce atherosclerosis for 14 weeks. Then

the size of aortic atherosclerotic lesions and the ratio of aortic tunica intima to media were measured. RT-PCR

immunohistochemistry and Western blotting were used for COX-2 mRNA and protein levels respectively.    Results  Compared with Group HC

atherosclerotic lesion size was markedly reduced in Groups M and H (P0.01). Compared with Group HC

the ratio of aortic tunica intima to media was significantly reduced in Groups H and M (P0.01). COX-2 mRNA expression was significantly higher in Group HC than that of control group

groups H and M (P0.01). COX-2 protein was higher in Group HC than that in Groups M and H (P0.01).    Conclusion  COX-2 participates in the genesis and development of atherosclerosis. Irbesartan at certain dosage can decrease the expression of COX-2.