Effect of angiotensin-converting enzyme inhibition on human tissue renin

This investigation was performed to assess the effect of treatment with an angiotensin-converting enzyme (ACE) inhibitor, ramipril, on human tissue renin levels. A total of 41 patients were studied (32 males and 9 females, aged 48-71 years). Twenty-two of these patients received up to 5 days treatment with the ACE inhibitor ramipril (5 mg p.o.) prior to surgery, the remaining 19 patients served as controls (no ramipril treatment). Under surgery vascular tissues were removed and renin-like activities measured in carotid and renal arteries. Plasma renin and ACE activity were determined before and after surgical intervention. Vascular renin values were two- to threefold higher in ACE-treated hypertensive patients compared to normotensive and untreated hypertensive controls (irrespective of concomitant atherosclerotic lesions). There were no differences in vascular renin observed between primary (essential) and secondary hypertension. In the hypertensive patients treated with ramipril, blood pressures were markedly (but not significantly) lowered in 12 patients. A similar pattern was observed for treatment-induced changes in plasma renin (increased) and ACE activity (decreased). The findings of this study demonstrate that treatment with an ACE inhibitor, such as ramipril, evokes changes in extrarenal tissues similar to those demonstrable in plasma. Conceivably, the blood pressure-lowering effect of ACE inhibition on human tissue is partially induced at the vascular level.