title: The guinea-pig trachea O-methylating system is more effective in modulating beta 2- than beta 1-adrenoceptor-mediated responses to isoprenaline.
abstract: Assuming that responses of the guinea-pig trachea to isoprenaline in the presence of atenolol (10 mumol L-1) are exclusively, or at least predominantly, beta 2-adrenoceptor mediated and that responses to isoprenaline in the presence of ICI 118,551 (erythro-DL-1(7-methylindan-4-yloxyl)-3-isopropylaminobut an-2-ol) (1 nmol L-1) are exclusively, or at least predominantly beta 1-adrenoceptor mediated, the influence of inhibition of COMT by U-0521 (dehydroxy-2-methyl propiophenone) (50 mumol L-1) has been compared in both conditions. U-0521 enhanced beta 2-adrenoceptor mediated responses to isoprenaline 3.3-fold, while those mediated by beta 1-adrenoceptors were enhanced only 2.2-fold. It is concluded that in guinea-pig trachea COMT activity is functionally more effective in modulating responses which are mediated by beta 2-adrenoceptors than responses mediated by beta 1-adrenoceptors.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008745:Methylation; D009126:Muscle Relaxation / Q000187:drug effects; D011412:Propanolamines / Q000494:pharmacology; D011427:Propiophenones / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D014132:Trachea / Q000378:metabolism / Q000502:physiology*
chemical_list: D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011427:Propiophenones; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; D001262:Atenolol; C006104:U 0521; D007545:Isoproterenol