Inhibitory effect of valves on endothelium-dependent relaxations to calcium ionophore in canine saphenous vein.
Responsiveness of superficial hand veins to local infusions of noradrenaline was compared in patients with primary varicose veins and in healthy volunteers by use of the dorsal hand vein technique. Patients with varicose veins required significantly higher doses of noradrenaline for half-maximal venoconstriction than the dose required by control subjects (geometric mean, 11.6 ng/min in patients compared with 4.8 ng/min in control subjects; p = 0.006). Noradrenaline responsiveness in varicose veins was not significantly different from hand vein responsiveness in the same patients. Our findings indicate a constitutional decrease in venous alpha-adrenergic receptor responsiveness in patients with varicosities. Dilation of varicose veins does not further affect noradrenaline-induced venoconstriction.