Characterization of the receptor mediating the antianaphylactic effects of beta-adrenoceptor agonists in human lung tissue in vitro.

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