Vascular angiotensin conversion in humans.
Studies were performed in normotensive volunteers and hypertensive subjects to examine the effect on forearm blood flow (FBF) of brachial artery infusions of angiotensin I (ANG I), angiotensin II (ANG II), and ramiprilat [the active metabolite of the angiotensin converting enzyme (ACE) inhibitor, ramipril]. Ramiprilat (10 mcg/min for 10 min) produced a 71% mean increase in FBF (n = 8; range, 26-130%; p less than 0.001) in vessels preconstricted with ANG I (64-128 pmol/min), with the effect maximal at the end of ramiprilat infusion and subsiding over 30 min. Doses of ANG I required to produce equivalent reductions of FBF were 2 to 4 times those of ANG II before ramiprilat, but after ramiprilat the dose of ANG I required to produce equivalent constriction was increased 20-fold (n = 6; p = 0.01) while that of ANG II was unaltered. Ramiprilat given alone produced only a small nonsignificant increase in FBF of 7 +/- 4% (n = 12; p = 0.29), though this increase did correlate significantly with plasma renin (r = 0.60; p = 0.04). These results confirm the presence of ACE within human resistance vessels and suggest the possibility that inhibition of ACE at sites other than the pulmonary bed might contribute to the hypotensive action of ACE inhibitors.
D000328:Adult; D000803:Angiotensin I / Q000494:pharmacology*; D000804:Angiotensin II / Q000494:pharmacology*; D000806:Angiotensin-Converting Enzyme Inhibitors; D005542:Forearm / Q000098:blood supply; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D007700:Kinetics; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D011758:Pyrroles / Q000494:pharmacology; D017257:Ramipril / Q000031:analogs & derivatives*; D012016:Reference Values; D012039:Regional Blood Flow / Q000187:drug effects; D012083:Renin / Q000097:blood
D000806:Angiotensin-Converting Enzyme Inhibitors; D011758:Pyrroles; D000804:Angiotensin II; C052549:ramiprilat; D000803:Angiotensin I; D007703:Peptidyl-Dipeptidase A; D012083:Renin; D017257:Ramipril