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

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 pA 2 values with both agonists. pA 2 values were consistenly at the high end of the range expected for interaction at a β 2 ‐adrenoceptor. 3 Practolol did not antagonize isoprenaline in a competitive manner but was a competitive antagonist of salbutamol with a pA 2 at the high end of the range expected for interaction at a β 2 ‐adrenoceptor. 4 Data obtained with agonists are consistent with the receptor being of the β 2 ‐subtype. Data obtained with antagonists indicate a consistently higher affinity for the receptor than observed for the β 2 ‐subtype in other tissues but do not suggest a novel β‐adrenoceptor subtype on the mast cell of the human lung.