Abstract: AIM: To investigate the relationship of cardiac remodeling and expression of angiotensin-converting enzyme (ACE) 2 mRNA in spontaneously hypertensive rats (SHRs). METHODS: Eighteen male (12 weeks of age) SHRs and 18 male (12 weeks of age) Wistar Kyoto (WKY) rats were randomly divided into two groups: WKY control group (n=18) and SHR group (n=18). Nine rats were randomly selected from each group and sacrificed immediately, whereas the other nine rats in each group were sacrificed 12 weeks later. Heart weight/body weight (HW/BW) was measured and mRNA expression of ACE2 was determined by real-time quantitative RT-PCR in all rats. RESULTS: HW/BW in 12- and 24-week-old SHRs increased compared with WKY rats (P<0.01, P<0.01). HW/BW in 24-week-old SHR rats increased compared with 12-week-old SHRs (P<0.05). Myocardial expression of ACE2 mRNA in 12- and 24-week-old SHR rats was significantly lower than in WKY rats (P<0.01, P<0.01). Myocardial expression of ACE2 mRNA in 24-week-old SHRs was significantly lower than in 12-week-old SHRs (P<0.01). CONCLUSION: Cardiac remodeling is related to expressions of ACE2 mRNA in SHRs.