Prevention of salt induced hypertension and fibrosis by angiotensin converting enzyme inhibitors in Dahl S rats

Background and purpose: In Dahl S rats, high salt increases activity of the tissue renin‐angiotensin‐aldosterone system (RAAS) in the CNS, heart and kidneys. Here, we assessed the effects of chronic angiotensin converting enzyme (ACE) inhibition on salt‐induced hypertension and cardiovascular and renal hypertrophy and fibrosis, relative to the extent of ACE blockade. Experimental approach: From 4.5 weeks of age, Dahl S rats received either the lipophilic ACE inhibitor trandolapril (1 or 5 mg kg ‐1 day ‐1 ) or the hydrophilic ACE inhibitor lisinopril (10 or 50 mg kg ‐1 day ‐1 ) and a high salt diet was started 0.5 week later. Treatments ended at 9 weeks of age. Key results: High salt diet markedly increased blood pressure (BP), decreased plasma angiotensin II and increased ACE binding densities in brain, heart, aorta and kidneys. Trandolapril and lisinopril prevented 50% of the increase in BP in light and dark period of the day. After the last doses, trandolapril decreased ACE densities by ∼80% in brain nuclei and heart and lisinopril by ∼60% in the brain and by ∼70% in the heart. The two ACE inhibitors prevented right ventricular hypertrophy and attenuated left ventricular hypertrophy but did not affect renal hypertrophy caused by high salt. Both drugs prevented high salt‐induced fibrosis in heart, kidney and aorta. Conclusion and implication: As the ACE inhibitors could completely prevent tissue fibrosis and partially prevent tissue hypertrophy and hypertension, the tissue RAAS may play a critical role in salt‐induced fibrosis, but a lesser role in the hypertrophy. British Journal of Pharmacology (2007) 152 , 903–914; doi: 10.1038/sj.bjp.0707472 ; published online 1 October 2007