CHARACTERIZATION OF THE RECEPTOR MEDIATING THE ANTI‐ANAPHYLACTIC EFFECTS OF β‐ADRENOCEPTOR AGONISTS IN HUMAN LUNG TISSUE in vitro

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Abstract
1 The rank order of potency of six β-adrenoceptor agonists as inhibitors of the anaphylactic release of histamine from fragments of passively sensitized human lung in vitro was (-)-isoprenaline > (-)-adrenaline > (±)-salbutamol > (-)-noradrenaline > R0363 > H133/22. 2 The β-adrenoceptor antagonists, propranolol, atenolol and H35/25, blocked the response to both (-)-isoprenaline and (±)-salbutamol competively. Each antagonist gave similar pA2 values with both agonists. pA2 values were consistenly at the high end of the range expected for interaction at a β2-adrenoceptor. 3 Practolol did not antagonize isoprenaline in a competitive manner but was a competitive antagonist of salbutamol with a pA2 at the high end of the range expected for interaction at a β2-adrenoceptor. 4 Data obtained with agonists are consistent with the receptor being of the β2-subtype. Data obtained with antagonists indicate a consistently higher affinity for the receptor than observed for the β2-subtype in other tissues but do not suggest a novel β-adrenoceptor subtype on the mast cell of the human lung.