Abstract: AIM: To investigate the expression of angiotensin-converting enzyme 2 (ACE₂) in the renal of spontaneously hypertensive rats and the effects of angiotensin type-1 receptor blockade. METHODS: Twenty of 14-week-old male SHR were randomly divided into two groups (n =10 in each): SHR group and irbesartan group. Ten of 14-week-old male WKY group were served as control. Irbesartan group were given a daily dose of 50 mg·kg^-1 irbesartan for 12 weeks by gavage and the other two groups were fed with a normal diet. Angiotensin-converting enzyme 2 was examined by immunohistochemistry and RT-PCR. RESULTS: ACE₂ in the renal was significantly down-regulated in the SHR group compared with the WKY group (0.72 ±0.11 vs 1.11 ±0.15). After 12 weeks treatment with irbesartan, the attenuated ACE₂ expression in irbesartan group was markedly enhanced compared with the SHR group (1.03 ±0.13 vs 0.72 ± 0.11). CONCLUSION: Hypertension induces the reduction of ACE₂ in the renal in rats and irbesartan markedly increases ACE₂ expression. It suggests that up-regulation ACE₂ which is one of counter-regulatory particular components in the renin-angiotensin system may be a new mechanism of curing hypertension beyond blockade angiotensin type-1 receptor.

Key words: spontaneously hypertensive rat, angiotensin-converting enzyme 2, renal, angiotensinII, irbesartan