title: Differences in alpha-adrenergic responsiveness between human internal mammary arteries and saphenous veins.
abstract: Little is known regarding specific biologic and pharmacologic differences between human internal mammary arteries and saphenous veins. To better define the role of alpha-adrenoceptor-mediated vasoconstriction in human internal mammary arteries and saphenous veins, we obtained fresh specimens of both vessels from 32 patients undergoing coronary artery bypass surgery. Dose-response curves were generated for the relatively selective alpha 1-receptor agonist phenylephrine, the alpha 2-receptor agonist BHT-920, and the alpha 1- and alpha 2-receptor agonist norepinephrine. Phenylephrine elicited similar contractile responses in internal mammary arteries and saphenous veins, with a mean EC50 (the effective concentration necessary to produce 50% of the maximal contraction) of 1.4 X 10(-6) M for internal mammary arteries and 1.8 X 10(-6) M for saphenous veins (p = NS). Selective stimulation of alpha 2-receptors with BHT-920 elicited a marked contractile response only in saphenous veins. Dose-response curves for phenylephrine and BHT-920 were shifted to the right for both vessels in the presence of the alpha 1-receptor antagonist prazosin and the alpha 2-receptor antagonist yohimbine, respectively. Norepinephrine elicited contraction at a lower concentration in saphenous veins than in internal mammary arteries with a mean EC50 of 7.8 X 10(-8) M for saphenous veins and a mean EC50 of 3.4 X 10(-7) M for internal mammary arteries (p less than 0.05). The results suggest that alpha-adrenoceptor-mediated vasoconstriction is caused primarily by alpha 1-receptors in human internal mammary arteries and by alpha 1- and alpha 2-receptors in human saphenous veins.
authors.affiliation: Charles A. Dana Research Institute, Beth Israel Hospital, Boston, MA 02215.
authors.forename: J S
authors.initials: JS
authors.lastname: Weinstein
authors.forename: W
authors.initials: W
authors.lastname: Grossman
authors.forename: R M
authors.initials: RM
authors.lastname: Weintraub
authors.forename: R L
authors.initials: RL
authors.lastname: Thurer
authors.forename: R G
authors.initials: RG
authors.lastname: Johnson
authors.forename: K G
authors.initials: KG
authors.lastname: Morgan
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000368:Aged; D001381:Azepines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008323:Mammary Arteries / Q000294:innervation*; D008875:Middle Aged; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012501:Saphenous Vein / Q000294:innervation*; D013895:Thoracic Arteries / Q000294:innervation*; D014654:Vascular Patency; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D000316:Adrenergic alpha-Agonists; D001381:Azepines; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; C024763:talipexole; D009638:Norepinephrine