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Effects of β‐adrenoceptor agonists in human bronchial smooth muscle
Author(s) -
Nials A.T.,
Coleman R.A.,
Johnson M.,
Magnussen H.,
Rabe K.F.,
Vardey C.J.
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.tb13929.x
Subject(s) - isoprenaline , agonist , formoterol , clenbuterol , potency , endocrinology , fenoterol , medicine , guinea pig , salbutamol , salmeterol , chemistry , practolol , intrinsic activity , schild regression , atenolol , pharmacology , terbutaline , receptor , propranolol , stimulation , copd , in vitro , asthma , biochemistry , blood pressure , budesonide
1 We have investigated the potency and duration of action of isoprenaline and a range of β‐adrenoceptor agonists as relaxants of inherent tone in human superfused, isolated bronchial smooth muscle, a tissue reported to contain a homogeneous population of β 2 ‐adrenoceptors. 2 All of the β‐adrenoceptor agonists caused concentration‐related inhibition of inherent tone, with isoprenaline having an EC 50 of 27 n m . The rank order of agonist potency was: formoterol ≥‐salmeterol ≥ clenbuterol > fenoterol = isoprenaline > terbutaline ≥ salbutamol > quinprenaline. 3 Relaxant responses to salmeterol were fully reversed by the selective β 2 ‐adrenoceptor blocking drug, ICI 118551, demonstrating the involvement of β 2 ‐adrenoceptors. 4 Rt 50 , i.e. the time taken for 50% recovery from the effects of an EC 50 concentration of agonist, differed considerably between the different β 2 ‐adrenoceptor agonists. Most agonists were short‐acting, having Rt 50 values less than 13 min. Quinprenaline was of moderate duration, with an Rt 50 value of ≥ 20 min. In contrast, salmeterol was extremely long‐acting, with no sign of recovery within 4 h. 5 Estimates of relative potency and duration of action were similar to those previously determined for these agonists in the guinea‐pig isolated trachea. These results suggest, therefore, that guinea‐pig trachea is a suitable alternative to human bronchus for the evaluation of the actions of β‐adrenoceptor agonists on airways smooth muscle.