AJP - Heart and Circulatory Physiology, Vol 246, Issue 2 239-H244, Copyright © 1984 by American Physiological Society
Effect of renin-angiotensin system on limb circulation in normal subjects
M. A. Creager, D. P. Faxon, S. M. Rockwell, J. C. Melby, H. Gavras and J. D. Coffman
It is not known whether the renin-angiotensin-aldosterone (RAA) system
contributes to the regulation of the limb circulation in normal human
beings. Accordingly, the effect of the angiotensin converting-enzyme
inhibitor, captopril, on forearm vascular resistance (FVR) and forearm
venous volume (FVV) was studied in nine normal subjects during states of
both sodium loading and sodium depletion. All subjects were studied in the
supine position and during 60 degrees head-up tilt. By analysis of
variance, the combined intervention of sodium depletion and
converting-enzyme inhibition was responsible for a decrease in both FVR and
mean blood pressure (BP). In sodium-depleted subjects, converting-enzyme
inhibition decreased supine mean BP 7.0% and supine FVR 22.8% but did not
change FVV. Neither the fall in BP nor the fall in FVR, however, was
significantly augmented by tilting from a supine to upright posture. In
sodium-loaded subjects, captopril did not alter BP, FVR, or FVV in
recumbent or upright positions. Therefore, the RAA system contributes to
the maintenance of blood pressure and limb vascular resistance only in
sodium-depleted subjects. Limb venous capacitance in normal subjects is not
regulated by the RAA system.
