Molecular pharmacology of beta-adrenoceptors

The development of radioligand-binding studies has greatly advanced our knowledge of the molecular pharmacology of beta-adrenoceptors. With this technique it is possible for the first time to directly determine the tissue concentration of beta-adrenoceptors, and by this, the responsiveness of tissues to beta-adrenergic stimulation. One major insight into the molecular pharmacology of beta-adrenoceptors to come from radioligand-binding studies was that the tissue concentration of beta-adrenoceptors is not a fixed number, but is rather dynamically regulated by a variety of drugs, hormones, physiological and pharmacological conditions. Since changes in beta-adrenoceptors assessed in circulating lymphocytes of man mirror changes in density and functional responsiveness of the corresponding myocardial beta-adrenoceptors, alterations in beta-adrenoceptor function can be also studied in human beings. In addition, by means of radioligand-binding studies the coexistence of beta 1- and beta 2-adrenoceptors has been demonstrated in numerous tissues of various species, including human heart and lung. The detailed knowledge of distribution and regulation of beta-adrenoceptors should help to improve the individual effectiveness of drug treatment.