Role of the Renin-Angiotensin System in Blood Pressure Regulation: The Cardiovascular Effects of Converting Enzyme Inhibition in Normotensive Subjects

• Published in: Circulation research 1979-12, Vol.45 (6), p.829-837
• Main Authors: NIARCHOS, ANDREAS P, PICKERING, THOMAS G, CASE, DAVID B, SULLIVAN, PATRICIA, LARAGH, JOHN H
• Format: Article
• Language: English
• Subjects: Adult; Angiotensin II - pharmacology; Blood Pressure - drug effects; Cardiac Output - drug effects; Female; Hemodynamics - drug effects; Humans; Male; Middle Aged; Oligopeptides - pharmacology; Renin - blood; Renin - pharmacology; Sodium - deficiency; Sodium - metabolism; Stroke Volume - drug effects; Teprotide - pharmacology; Vascular Resistance - drug effects
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.45.6.829

The role of the renin-angiotensin system in the regulation of blood pressure in normal human subjects was investigated by administering to them the converting enzyme inhibitor (SQ 20881) during sodium-replete and sodium-depleted states. In the sodium-replete state (150 m£q sodium intake for 5 days) in eight normal subjects, converting enzyme inhibitor decreased the average mean arterial pressure from 75 ± 4 to 65 ± 5 mm Hg (P < 0.005) because of a decrease in peripheral resistance from 17 ± 1 to 14 ± 1 U (P < 0.025). Cardiac output did not change because of a simultaneous decrease in venous return. Sodium depletion (10 mEq sodium intake for 5 days) in six subjects resulted in an insignificant decrease in blood pressure (from 75±4to69± 2 mm Hg), whereas cardiac output decreased from 5.15 ± 0.29 to 3.91 ± 0.22 liters/min (P < 0.05). Plasma renin activity increased with sodium depletion from 2.13 ± 0.38 to 7.3 ± 1.3 ng/ml per hour (P< 0.005). Converting enzyme inhibitor administration in the sodium-depleted state (n » 8) decreased mean arterial pressure from 69 ± 2 to 53 ± 5 mm Hg (P < 0.005) because of a decrease in peripheral resistance from 18 ± 1 to 12 ± 1 U (P < 0.005), whereas cardiac output increased from 3.91 ± 0.33 to 4.40 ± 0.30 liters/min (P < 0.005). The maximum decrease in diastolic blood pressure caused by the inhibitor correlated to the control plasma renin activity (r = 0.76, P < 0.01, n =· 14 measurements). These results indicate that the renin-angiotensin system participates in the regulation of blood pressure and cardiac function in normal subjects, even in the sodium-replete state. This role of the renin-angiotensin system in cardiovascular homeostasis in normal subjects becomes more crucial during sodium depletion when plasma renin (angiotensin II) is markedly increased. Cux Res 45:839-837, 1979