The role of plasma angiotensin I converting enzyme in regulation of renin-angiotensin system activity in patients with essential hypertension.

: In order to investigate the role of plasma angiotensin I (pAI) converting enzyme on the activity of the renin-angiotensin system, we measured plasma renin activity (PRA), plasma angiotensin II (pAII), and plasma angiotensin I converting enzyme (pACE) activity in fourteen patients with essential hypertension before and after two hours of ambulation combined with intravenous furosemide administration. Significant increases were observed in the values of PRA (p less than 0.005), pAII (p less than 0.005) and ACE activity (p less than 0.05) after ambulation. The ratios of log pAII/log PRA were increased significantly after ambulation (p less than 0.005), and a significantly positive correlation was observed between log pAII/log PRA and ACE activity (p less than 0.01). These results suggested that not only PRA but also ACE activity contributed to the activity of renin-angiotensin system through the generation of AII.