Angiotensin II augments sympathetically induced venoconstriction in man.
1. The constriction produced by a single deep breath was measured simultaneously in two adjacent hand veins in normal volunteers. One vein was infused with angiotensin II (ANG II) while the other acted as a control. 2. At a dose lower than that required to produce direct venous constriction (1 pmol/min), ANG II significantly augmented the constriction caused by a deep breath in eight subjects (P less than 0.01). The same dose had no effect on the venoconstriction caused by infused noradrenaline (NA) in a further six subjects. 3. It is concluded that ANG II at low doses may cause venoconstriction indirectly by augmenting sympathetically induced venous tone via a presynaptic mechanism. This observation may help to explain the apparent venodilating property of angiotensin-converting enzyme inhibitors in clinical situations where the renin-angiotensin system is stimulated.
Benjamin
N
N
Department of Medicine, St George's Hospital Medical School, London.
Collier
J G
JG
Webb
D J
DJ
D000328:Adult; D000804:Angiotensin II / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006225:Hand / Q000098:blood supply; D006801:Humans; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D012018:Reflex / Q000187:drug effects; D012119:Respiration; D013564:Sympathetic Nervous System / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects*; D014680:Veins / Q000502:physiology
D000804:Angiotensin II; D009638:Norepinephrine; D010646:Phentolamine