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Classification of β‐adrenoceptors in isolated bronchus of the pig
Author(s) -
Goldie Roy G.,
Paterson James W.,
Wale Janet L.
Publication year - 1983
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.1476-5381.1983.tb10510.x
Subject(s) - agonist , atenolol , fenoterol , partial agonist , carbachol , chemistry , isoprenaline , propranolol , endocrinology , schild regression , medicine , potency , pharmacology , receptor , biology , stimulation , biochemistry , in vitro , asthma , blood pressure
1 (±)‐Isoprenaline (Iso), (−)‐adrenaline (Ad), (−)‐noradrenaline (NA), the β 2 ‐selective adrenoceptor agonist (±)‐fenoterol (Fen) and the β 1 ‐selective adrenoceptor agonist (±)‐RO363 caused concentration‐dependent relaxation of preparations of pig bronchus pre‐contracted with carbachol 40 ng/ml (0.22 μ M ). Iso, Ad, NA and Fen caused complete relaxation of carbachol‐induced tone, but RO363 caused relaxation equivalent to only 59% of the maximal response to Iso. 2 When relaxation responses to these amines were plotted as a % of their maximal effects, comparison of EC 50 values showed that the order of potency was RO363 > Iso > NA > Fen > Ad (14.4:4.6:1:0.4:0.3). 3 pA 2 values determined for the β‐adrenoceptor antagonists propranolol (non‐selective) and atenolol (β 1 ‐selective), or the partial agonist salbutamol (β 2 ‐selective) using Iso as agonist were 8.3, 7.3 and 4.4 respectively. The pA 2 value for atenolol using RO363 as the agonist was 7.6. 4 These results indicate that porcine bronchus contains a homogeneous population of β 1 ‐adrenoceptors.