Responses of isolated canine and simian femoral arteries and veins to phenylephrine, xylazine and KCI after removal of endothelium

Using the cannula inserting method, vasoconstrictor responses to phenylephrine (an alpha 1-adrenoreceptor agonist), xylazine (an alpha 2-adrenoreceptor agonist) and KCl after removal of the endothelium by intraluminal treatment with saponin were investigated in isolated and perfused canine and simian femoral arteries and veins. In arteries, vasoconstrictor responses to KCl were markedly potentiated by removal of the endothelium in both species. KCl-induced vasoconstrictions were not modified by treatment with an alpha 1-adrenoreceptor antagonist, bunazosin, which blocked noradrenaline-induced constrictions. The phenylephrine-induced constriction was significantly potentiated by removal of the endothelium in simian arteries but not in canine arteries. In both arteries, responses to xylazine were not influenced by removal of the endothelium. In femoral veins of both species, responses to phenylephrine, xylazine and KCl were not significantly modified by a relatively small dose of saponin but were moderately depressed by a large dose. It is suggested that the endothelium may play an important role for inducing alpha 1-adrenoreceptor-mediated constrictor responses in simian femoral arteries, but not in canine arteries or in either vein tested.