Dependence of constrictor and dilator humoral responses of arteries and veins in the small intestine on calcium ions entering vascular myocytes

Verapamyl administered to the intestine circulation in the dose evoking no shifts in the arterial and venous resistance or in the vascular capacity, decreased 2- or 3-fold both the constrictor and dilatory responses of the arterial vessels. Against the background of Verapamyl, noradrenaline and isoproterenol did not practically change either capacity or resistance in the veins. Responses of veins to angiotensin II increased 10-fold and more, whereas they were absent after administration of atropine into the intestine circulation. Constrictor and dilatory responses of veins need to a greater extent than the arteries penetration of external calcium ions to their myocytes.