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Inter-regulation between components of the renin-agiotensin system (RAS) is common, but little is known about the direct regulatory effects on cardiac ACE2-Mas axis.This study was to determine if the cardiac ACE2, ACE and Mas levels change in hypertensive rats treated with enalapril and losartan.Forty rats were divided into 4 groups: sham operated (n=10), rats with the aortic coarctation (AC, n=10), AC rats fed enalapril (20 mg/kg·d-1,n=10), and AC rats fed losartan (30mg/kg·d-1, n=10).MAP was recorded using a tail-cuff method.After 22-day treatment, levels of ACE2, ACE and Mas receptor in the heart and PRA were examined by RT-PCR, western blot and radioimmunoassay.Cardiac ACE mRNA and ACE protein levels were greater in AC rats than in the control (P<0.05).In AC rats with enalapril, cardiac ACE mRNA and its protein levels were decreased (P<0.01), but losartan did not affect their levels.However, cardiac ACE2 levels were lower in AC rats than in the control (P<0.01).Both enalapril and losartan increased the levels of cardiac ACE2 expression.Mas mRNA rose in AL rats treated with losartan, but not enalapril.Our findings demonstrate that enalapril and losartan increase the ratio of cardiac ACE2/ACE mRNA levels.Losartan significantly elevates the cardiac ACE2 and Mas expression but not enalapril.These results suggest that AT1 blockade increases the activity of the cardiac ACE2-Ang (1-7)-Mas axis of the RAS.