Postjunctional alpha 1- and alpha 2-adrenoceptors mediating contraction in isolated human groin arteries and veins.
By means of selective agonists and antagonists for alpha 1- and alpha 2-receptors, the alpha-receptor subtypes in human groin arteries and veins were characterized and compared. In the arteries the alpha 1-receptor blocker prazosin caused a concentration-dependent parallel displacement of the noradrenaline (NA) concentration-response (cr) curve without reduction of maximum (pA2 = 9.86); the selective alpha 2-receptor antagonist rauwolscine in the concentration 10(-8) M caused a right-ward shift of the NA cr-curve without reduction of Emax, but 10(-7) M and 10(-6) M caused little or no further shift. In the veins, the two antagonists had the opposite effects. Rauwolscine caused a concentration-dependent right-ward shift of the NA cr-curve without depression of maximum (pA2 = 9.03); prazosin 10(-9) M significantly displaced the NA cr-curve, whereas 10(-8) M and 10(-7) M caused little or no further shift. The responses to the alpha 2-receptor agonist clonidine in the arteries were too small to allow calculations of pEC50 values; in the veins contractions were elicited in all vessel segments investigated (pEC50 = 6.24). Phenylephrine, selective for alpha 1-receptors, was significantly more potent in arteries than in veins. NA was significantly more potent in veins than in arteries. It is concluded that in human groin vessels, there is a functional predominance of alpha 1-receptors in the arteries and of alpha 2-receptors in the veins.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000328:Adult; D000368:Aged; D001158:Arteries / Q000187:drug effects / Q000294:innervation; D005260:Female; D006119:Groin / Q000098:blood supply*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D011942:Receptors, Adrenergic, alpha / Q000145:classification*; D014661:Vasoconstriction / Q000187:drug effects; D014680:Veins / Q000187:drug effects / Q000294:innervation
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha