EXOSITES - THEIR CURRENT STATUS, AND THEIR RELEVANCE TO THE DURATION OF ACTION OF LONG-ACTING BETA(2)-ADRENOCEPTOR AGONISTS

The four beta(2)-adrenoceptor agonists, clenbuterol, bambuterol, formo terol and salmeterol, are all long-acting bronchodilators, that have d istinct mechanisms for their extended durations of action. Various the ories have been put forward in an attempt to explain these mechanisms. In this respect, there is strong evidence for the existence of specif ic additional binding sites (exosites) for salmeterol and related comp ounds, and that exosites exist on non-ligand recognition regions of th e beta(2)-adrenoceptor protein. Here, Robert Coleman and colleagues co mpare and contrast the profiles of action of these long-acting beta(2) -adrenoceptor agonists, particularly as they relate to the role of exo sites.