Salmeterol inhibition of mediator release from human lung mast cells by β‐adrenoceptor‐dependent and independent mechanisms

1 The long‐acting β2‐adrenoceptor agonist, salmeterol (10−9–10−5 M), inhibited the IgE‐mediated release of histamine from human lung mast cells (HLMC) in a dose‐dependent fashion. Additional β‐adrenoceptor agonists were studied and the rank order of potency for the inhibition of histamine release from HLMC was isoprenaline>salmeterol>salbutamol. Approximate EC50 values for the inhibition of histamine release were 10 nM for isoprenaline and 100 nM for salbutamol. An EC50 value for salmeterol could not be calculated because maximal responses to salmeterol were not observed over the concentration range employed. 2 Both salmeterol and isoprenaline inhibited the generation of sulphopeptidoleukotrienes (sLT) more potently and more efficaciously than the release of histamine from immunologically‐activated HLMC. Salmeterol (EC50