title: A difference in mode of antagonism between optical isomers of a potent selective alpha 1-adrenoceptor blocker (YM-12617) and norepinephrine in isolated rabbit iris dilator and aorta.
abstract: Optical isomers of YM-12617, a potent and selective alpha 1-adrenoceptor blocker, were tested on the rabbit iris dilator and aorta. The order of potency was R(-)-isomer greater than racemate greater than S(+)-isomer. The R(-)-isomer and racemate behaved as an essentially irreversible antagonist to norepinephrine in the iris dilator where the efficacy of norepinephrine was small, although the S(+)-isomer was a competitive antagonist. These drugs behaved as a competitive antagonist of norepinephrine in the aorta where the efficacy of norepinephrine was large.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007498:Iris / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D011817:Rabbits; D013237:Stereoisomerism; D013449:Sulfonamides / Q000494:pharmacology*; D000096926:Benzenesulfonamides
chemical_list: D000317:Adrenergic alpha-Antagonists; D009638:Norepinephrine; D013449:Sulfonamides; C044648:YM 12617; D000096926:Benzenesulfonamides