Augmentation of sympathetic venoconstriction by angiotensin II in human dorsal hand veins

The constriction produced by a single deep breath was measured simultaneously in two adjacent hand veins in normal subjects. One vein was infused with saline or angiotensin II; the other acted as a control. A dose of angiotensin II (1 pmol/min) that did produce venous constriction directly significantly augmented the constriction caused by deep breath in eight subjects (P less than .01). In a further six subjects the same dose had no effect on venoconstriction caused by infused noradrenaline. We conclude that angiotensin II causes venoconstriction indirectly by augmenting sympathetically mediated responses, possibly by a presynaptic mechanism.