Effects of Acetylstrophanthidin on Isolated Veins of the Dog

Acetylstrophanthidin, 1.0 to 10.0 µg/ml, caused contraction of strips of the lateral saphenous vein of the dog in an organ bath at 37°C. The superior mesenteric vein, which exhibited spontaneous activity in the organ bath, responded to acetylstrophanthidin with an almost immediate increase in tension and an increased frequency of contractions; this was followed by a sustained contraction which had the same time lag as the contraction of a saphenous vein strip from the same dog. In strips from both veins, the contraction was depressed by cooling and augmented by warming, an effect opposite to that seen with norepinephrine-induced contractions. A latent period of 10 to 60 minutes preceded the contraction of the saphenous vein; during this time, the vein showed increased reactivity to added norepinephrine, 5-hydroxytryptamine, acetylcholine, barium chloride, increased bath concentration of K + , and decreased bath concentration of Na + . The increased reactivity and contraction still occurred after catecholamine depletion of the vein by chronic lumbar sympathectomy and in umbilical veins, which are devoid of adrenergic nerves. In addition to its direct constrictor action on cutaneous and mesenteric veins, acetylstrophanthidin sensitized cutaneous veins to vasoactive agents and to changes in ionic environment. These actions did not depend on the presence of norepinephrine in the veins.