Investigations of the subtype of alpha 2-adrenoceptor mediating contractions of the human saphenous vein.
1. We have examined the effects of a series of alpha 2-adrenoceptor antagonists against isometric contractions to noradrenaline in human saphenous vein, and correlated these potencies with affinities for the alpha 2A-ligand binding site of human platelet and the alpha 2B-ligand binding site of rat kidney. 2. The alpha 2B-selective adrenoceptor antagonists, prazosin, ARC 239 and HV 723 showed high, and the alpha 2A-selective antagonist BRL 44408 showed low, potency in human saphenous vein. 3. Potency in human saphenous vein correlated better with affinity for the alpha 2B-ligand binding site (r = 0.71, n = 12, P less than 0.01) than with affinity for the alpha 2A-ligand binding site (r = 0.56, n = 12, non significant). 4. It is concluded that the postjunctional alpha 2-adrenoceptor of human saphenous vein resembles an alpha 2B-ligand binding site more than an alpha 2A-ligand binding site.
Department of Clinical Pharmacology, Royal College of Surgeons in Ireland, Dublin.
K
K
Smith
S
S
Connaughton
J R
JR
Docherty
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000328:Adult; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012501:Saphenous Vein / Q000187:drug effects / Q000502:physiology
D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha