Vasoconstrictor responses induced by alpha-adrenoreceptor agonists before and after removal of the endothelial cells of dog mesenteric arteries.

The stainless cannula inserting method was used to investigate the effects of alpha-adrenoreceptor agonists (phenylephrine, alpha 1-agonist and xylazine alpha 2-agonist) and calcium chloride on isolated and perfused dog mesenteric arteries with and without saponin treatment. By intraluminal administration, phenylephrine and calcium chloride caused vasoconstriction in a dose-related manner whilst xylazine was without significant effect. After intraluminal treatment with 3 mg of saponin, the endothelia of the arteries were completely removed as confirmed by pathological examinations. Phenylephrine- and xylazine-induced responses were not influenced by saponin treatment whereas calcium chloride-induced constriction was significantly enhanced.