Human Vascular Renin-Angiotensin System and Its Functional Changes in Relation to Different Sodium Intakes

Abstract —A growing body of evidence supports the existence of a tissue-based renin-angiotensin system (RAS) in the vasculature, but the functional capacity of vascular RAS was not investigated in humans. In 28 normotensive healthy control subjects, the metabolism of angiotensins through vascular tissue was investigated in normal, low, and high sodium diets by the measurement of arterial-venous gradient of endogenous angiotensin (Ang) I and Ang II in two different vascular beds (forearm and leg), combined with the study of 125 I-Ang I and 125 I-Ang II kinetics. In normal sodium diet subjects, forearm vascular tissue extracted 36±6% of 125 I-Ang I and 30±5% of 125 I-Ang II and added 14.9±5.1 fmol · 100 mL −1 · min −1 of de novo formed Ang I and 6.2±2.8 fmol · 100 mL −1 · min −1 of Ang II to antecubital venous blood. Fractional conversion of 125 I-Ang I through forearm vascular tissue was about 12%. Low sodium diet increased ( P 125 I-Ang I decreased from 12% to 6% ( P −1 · min −1 , respectively ( P 125 I-Ang I increased from 12% to 20% ( P