Objectives The discovery of angiotensin-converting enzyme 2 (ACE2) has greatly modified our understanding of renin-angiotensin system (RAS). This study aimed to investigate the cardiac expression of ACE2 and ACE in spontaneously hypertensive rats (SHR)

Methods Fifteen SHRs were randomly assigned to two groups: SHR control group (n = 7) which were treated with vehicle, and enalapril group (n = 8) treated with enalapril [15 mg/(kg·d)]. After 4 weeks of treatment, the rats were killed and the left ventricular tissue dissected carefully. Reverse transcription polymerase chain reaction and Western blot protein staining were performed to detect the expression of mRNA and protein of ACE2 and ACE. Ten WKY rats.

Results Compared with the normotensive WKY rats, the cardiac expression of both mRNA and protein of ACE in SHR was significantly increased (1.68 ± 0.34 vs 0.33 ± 0.12, P < 0.05;1.21 ± 0.14 vs 0.71 ± 0.11, P < 0.05), where as the cardiac levels of both mRNA and protein of ACE2 were significantly decreased (0.50 ± 0.15 vs 1.16 ± 0.24, P < 0.05; 0.71 ± 0.24 vs 1.22 ± 0.14, P < 0.05). After treatment with enalapril, the levels of both mRNA and protein of ACE were significantly decreased (0.44 ± 0.19 vs 1.68 ± 0.34, P < 0.01; 0.87 ± 0.13 vs 1.21 ± 0.14, P < 0.05) and the expression of ACE2 mRNA significantly elevated (1.77 ± 0.49 vs 0.50 ± 0.15, P < 0.05), but ACE2 protein remained unchanged.

Conclusions In SHR, the expression of cardiac ACE was remarkably increased, where as ACE2 was notably decreased. Reduction of ACE and elevation of ACE2 might be one of the mechanisms underlying the antihypertensive function of enalapril.