The influence of the renin-angiotensin system on adrenergic vasoconstrictor responses in the forearm and splanchnic region in sodium deplete man

Abstract

In sodium deplete subjects forearm (FBF) and splanchnic (SBF) blood flows were measured at rest and during lower body negative pressure (LBNP) before and during angiotensin II (ANG II) blockade. Both FBF and SBF were reduced by LBNP. Forearm blood flow and forearm vascular resistance were unaffected by ANG II blockade (intra-arterial saralasin, n = 6; i.v. enalapril, n = 9) both at rest and during LBNP. In contrast, resting SBF increased and splanchnic vascular resistance decreased after i.v. enalapril (n = 10). The low resistance was completely unchanged during the following LBNP. It is concluded that acute ANG II blockade has no influence on the vascular resistance in the human forearm, but increases basal SBF in sodium depleted subjects and 'paralyses' the vasoconstrictor response to LBNP.