title: A beta-adrenergic partial agonist (befunolol) discriminates two different affinity sites.
abstract: Interactions of beta-adrenergic partial agonists with the beta-adrenoceptor were studied in isolated guinea-pig taenia caecum. The competitive inhibition curve for specific binding of a high concentration (50 nM) of [3H]-befunolol by befunolol showed a biphasic shape, although the curve for specific binding of a low concentration (1 nM) was monophasic. All the competitive inhibition curves for specific binding of [3H]-befunolol (1 nM and 50 nM) by isoprenaline and propranolol showed monophasic shapes. These results suggest that befunolol may be able to discriminate two different binding sites of the beta-adrenoceptor: the high affinity site and the low affinity site.
mesh_terms: D000318:Adrenergic beta-Agonists / Q000378:metabolism*; D000319:Adrenergic beta-Antagonists / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002354:Carteolol / Q000494:pharmacology; D002432:Cecum; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000378:metabolism; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D011412:Propanolamines / Q000378:metabolism* / Q000494:pharmacology; D011433:Propranolol / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000145:classification / Q000378:metabolism*
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C006034:befunolol; D002354:Carteolol; D011433:Propranolol; D007545:Isoproterenol