Journal of Applied Physiology, Vol 53, Issue 3 576-581, Copyright © 1982 by American Physiological Society
Hemodynamic response to converting enzyme inhibition at rest and exercise in humans
R. Fagard, P. Lijnen, L. Vanhees and A. Amery
The response of the systemic circulation to acute inhibition of the
converting enzyme with 25 mg of oral Captopril (Squibb) was studied in six
normal sodium-replete male volunteers at rest and during exercise, together
with its effects on exercise capacity for graded uninterrupted exercise. In
recumbent subjects at rest Captopril did not affect arterial pressure or
heart rate, and plasma renin activity rose 2.5-fold (P less than 0.05). In
subjects in the sitting position, at rest and during exercise until
exhaustion, Captopril reduced mean brachial intra-arterial pressure by an
average of 7 Torr in comparison to placebo (P less than 0.001). Captopril's
hypotensive effect was caused by a reduction of systemic vascular
resistance (P less than 0.01), without changes of cardiac output (measured
by CO2 rebreathing), heart rate, or stroke volume. Plasma renin activity
was significantly higher during Captopril (P less than 0.001). Peak oxygen
uptake and exercise duration were the same after administration of
Captopril or placebo. The data demonstrate that the renin-angiotensin
system is not involved in the homeostasis of blood pressure in supine
sodium-replete humans, but has a modest role in blood pressure regulation
when posture is changed from supine to upright. The orthostatic effect of
Captopril is maintained during upright exercise. Furthermore the reduction
of systemic vascular resistance by Captopril does not affect peak oxygen
uptake.
