The effect of isoprenaline on adrenoceptors in human saphenous vein.
1. The order of potency of sympathomimetic amines in causing contraction of strips of human saphenous vein was (-)-adrenaline>(-)-noradrenaline>(-)-phenylephrine>(+/-)-isoprenaline.2. The competitive alpha-adrenoceptor blocking drugs tolazoline, phentolamine, and thymoxamine and the irreversible blocking drug phenoxybenzamine all blocked noradrenaline and isoprenaline contractions.3. Contractions produced by 5-hydroxytryptamine were also blocked by phentolamine and thymoxamine. Fenfluramine-induced contractions were not blocked by thymoxamine or phenoxybenzamine.4. ED50 contracting doses of isoprenaline did not cause consistent relaxation of noradrenaline-contracted strips.5. It is concluded that human saphenous vein contains a dominant population of alpha-adrenoceptors which can be stimulated by high doses of isoprenaline, but the occurrence of beta-adrenoceptors mediating relaxation is rare.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011955:Receptors, Drug; D012501:Saphenous Vein / Q000187:drug effects*; D013565:Sympatholytics / Q000494:pharmacology; D014043:Tolazoline / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D006873:Hydroquinones; D011955:Receptors, Drug; D013565:Sympatholytics; D010643:Phenoxybenzamine; D010656:Phenylephrine; D014043:Tolazoline; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine; D010646:Phentolamine