Unrelated responses of brachial artery hemodynamics and renin-angiotensin system to acute converting enzyme inhibition by enalaprilat in essential hypertension.

The simultaneous acute effects of converting enzyme inhibition by intravenous enalaprilat on the circulating renin-angiotensin system and on the brachial artery were studied in 12 hypertensive patients by a double-blind comparison with saline effects in 14 hypertensive patients. The brachial artery was investigated in terms of arterial section (measured by pulsed Doppler technique) and wall rigidity (assessed by pulse wave velocity). Arterial and biochemical parameters were measured in baseline before injection and at 20 to 40 minutes (t1) and 80 to 100 minutes (t2) after saline and drug injections. Compared with the saline vehicle, enalaprilat significantly decreased angiotensin enzyme converting activity (p less than 0.001), increased plasma renin activity (p less than 0.01) and decreased plasma aldosterone concentrations (p less than 0.01). The drug reduced blood pressure (p less than 0.01) and increased the brachial artery section (p less than 0.01), but did not change pulse wave velocity. In the enalaprilat group, significant postinjection relations were observed between: (1) enalaprilat concentration and plasma angiotensin converting enzyme activity (r = -0.72, p less than 0.001); (2) plasma renin activity and mean blood pressure (r = -0.46, p less than 0.02); (3) plasma enalaprilat concentration and pulse wave velocity (r = -0.50, p less than 0.01) and (4) pulse wave velocity and brachial artery section (r = 0.42, p less than 0.05). Thus, the brachial artery effects of enalaprilat were not directly related to the blockade of the renin-angiotensin system in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)