Therapeutic implications of beta-adrenergic receptor pharmacodynamic properties.

In the last decades new pharmacodynamic properties of beta-adrenoceptors have been discovered that could greatly impact in the use of beta-adrenergic agents in the clinical practice. Concepts such as multiple binding sites, constitutive activity, polymorphism and intracellular signaling of betaadrenoceptors may contribute in the discovery of more efficacious pharmacological agents for treatment of heart failure and asthma. beta-Adrenoceptors show a relative high constitutive activity in both cardiac and pulmonar tissues. Most beta-blockers exert an inverse agonist action that could contribute to their beneficial effects in the treatment of heart failure. Recently, the existence of multiple affinity sites has been described for beta1-adrenoceptor. It was proposed that beta-blockers that show agonist properties at the beta1L-adrenoceptors binding site may exert neutral or harmful effects when used for treatment of heart failure. Considering the cardiac effect of beta1L-adrenoceptors, activation of the low-affinity state of beta1-adrenoceptor could be deleterous in cardiovascular pharmacology. The ability of beta2-adrenoceptor to couple to Gs or Gi-protein gives the possibility that different agonists can activate different signaling cascades. Full beta2-adrenoceptor agonists would be highly useful for improvement bronchodilatation in the acute treatment of asthma. Polymorphic variants of beta-adrenoceptors have profound impact in the understanding of normal physiology and pathophysiology. Genotypic characterization of patients could improve selection of patients during beta-adrenergic pharmacotherapies. The aim of the present review is to describe new insights in pharmacological and biochemical properties of beta-adrenoceptors and their impact on the use of beta-adrenergic agents in the treatment of cardiovascular and respiratory diseases.