Vasopressin Induces Opposite Changes in Blood Flow in the Skin and the Muscular Circulation

Abstract

Arginine vasopressin (AVP) is a potent vasoconstrictor and antidiuretic neurohormone. that exerts biphasic effects on forearm blood flow. At low concentration, namely < 0.05 ng/kg/min, it induces a vasoconstriction whereas at higher concentration it produces a forearm vasodilation ¹. The mechanisms mediating forearm vasodilation are not fully understood. However, recent evidence strongly supports that V2 receptors are necessary because patients with nephrogenic diabetes insipidus do not exhibit forearm vasodilation following AVP administration into the brachial artery². More recently we reported an heterogeneous vascular response to AVP when two different methods of blood flow measurements were compared ³.Indeed, venous occlusion plethysmography revealed global forearm blood flow increase following high dose intraarterial AVP administration whereas a dose-dependent vasoconstriction was observed when radial artery blood flow was measured by combining high resolution echotracking radial artery diameter with continuous flow velocity measures. Skin blood flow measured by Laser Doppler flowmetry (LDF) paralleled the results obtained at the radial artery level. It was thus hypothesised that the discrepant data could result from opposing AVP responses between the muscular and the skin circulations. The purpose of this study was thus to test whether high dose AVP exhibit vasodilatory effects in the muscle and vasoconstriction in the skin by measuring simultaneous blood flow in both vascular beds following administration into the brachial artery. Vasoconstrictor (Angiotensin II) and vasodilator (DDAVP and nitroglycerin) drugs served as control.