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(—)‐CGP 12177‐induced increase of human atrial contraction through a putative third β‐adrenoceptor
Author(s) -
Kaumann Alberto J.
Publication year - 1996
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.1476-5381.1996.tb15159.x
Subject(s) - contraction (grammar) , adrenergic receptor , medicine , endocrinology , muscle contraction , pharmacology , receptor , chemistry
1 The inotropic effects of (−)−4‐(3‐ t ‐butylamino‐2‐hydroxypropoxy)benzimidazol‐2‐one ((−)−CGP 12177), an antagonist for β 1 ‐ and β 2 ‐adrenoceptors as well as an agonist for β 3 ‐adrenoceptors, were investigated on paced preparations of isolated right atrial appendages obtained from patients without advanced heart failure undergoing open heart surgery. 2 In the presence of (−)−propranolol (200 nM), (−)−CGP 12177 increased contractile force with a ‐log EC 50 , M, of 7.3. The maximum effects of (−)−CGP 12177 amounted to 15% and 11% of the effects of (−)−isoprenaline (400 μ m ) and of CaCl 2 (6.75 mM) respectively. 3 (—)‐Bupranolol 1 μ m , an antagonist with a p K B of ∼7.5 for β 3 ‐adrenoceptors, antagonized surmountably the positive inotropic effects of (—)‐CGP 12177 (in the presence of 200 nM (−)−propranolol) with an apparent p K B of 7.3. 4 The potent positive inotropic effects of (−)−CGP 12177 and their resistance to blockade by (−)−propranolol but antagonism by (−)−bupranolol are consistent with the existence in human atrial myocardium of a minor third β‐adrenoceptor population, possibly related to β 3 ‐adrenoceptors.