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The affinity of betaxolol, a β 1 ‐adrenoceptor‐selective blocking agent, for β‐adrenoceptors in the bovine trachea and heart
Author(s) -
Satoh Eisaku,
Narimatsu Akihiro,
Hosohata Yoshiaki,
Tsuchihashi Hiroshi,
Nagatomo Takafumi
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb12829.x
Subject(s) - betaxolol , atenolol , propranolol , medicine , endocrinology , beta (programming language) , antagonist , adrenergic receptor , pindolol , chemistry , beta 1 adrenergic receptor , timolol , receptor , blood pressure , surgery , intraocular pressure , computer science , programming language
1 The specificity of betaxolol, a β‐adrenoceptor antagonist, for β 1 and β 2 ‐adrenoceptors was compared with that of other β‐antagonists, atenolol, ICI‐118551, butoxamine and (±)‐propranolol, in the bovine trachea and heart by competitive interaction with [ 3 H]‐CGP12177 as a radioligand. 2 The radioligand K d values were 0.75 ±0.12 and 1.60 ± 0.11 n m in the trachea and heart, respectively, and the B max values were 34.00 ± 4.41 and 21.54 ± 2.94 fmol mg −1 protein, respectively. 3 Using ICI‐118551, we determined the ratio of β 1 :β 2 ‐adrenoceptors in the trachea and heart to be approximately 29:71 and 56:44, respectively. 4 In the trachea, a β 2 ‐predominant tissue, betaxolol and atenolol were more selective for β 1 ‐adrenoceptor binding sites than β 2 ‐adrenoceptor binding sites, whereas ICI‐118551 and butoxamine were more selective for β 2 ‐adrenoceptor binding sites. 5 The β 1 ‐selectivity of betaxolol was 2.2 and 2.7 fold higher than that of atenolol in the bovine trachea and heart. These findings suggest that betaxolol may be useful in the treatment of hypertension, cardiac arrhythmia and angina pectoris.