Beta-1 adrenergic receptor; Beta-2 adrenergic receptor (ADRB1; ADRB2)

Beta-1 adrenergic receptor and beta-2 adrenergic receptor are closely related **G protein-coupled receptors (GPCRs)** that mediate the physiological effects of catecholamines (primarily epinephrine and norepinephrine) in various tissues. Beta-1 adrenergic receptor is mainly found in the heart, where it regulates heart rate and contractility by coupling to Gs proteins, leading to cAMP production[6]. Beta-2 adrenergic receptor is widely expressed in smooth muscle (notably bronchi and vasculature), where it induces muscle relaxation and bronchodilation, playing a critical role in asthma therapy[1]. Both subtypes have structural similarities, including seven transmembrane domains, but pharmacological and functional differences[2][3]. Polymorphisms in the corresponding genes (ADRB1 and ADRB2) are associated with variations in drug response and susceptibility to disorders such as asthma, obesity, type 2 diabetes, and cardiovascular disease[1][6]. Agonists (e.g., salbutamol) activate these receptors, leading to bronchodilation or increased cardiac output; antagonists (beta-blockers, e.g., propranolol, metoprolol) inhibit sympathetic effects and are used in the management of hypertension, arrhythmias, and heart failure; inverse agonists decrease basal receptor activity[1][5]. Safety concerns primarily relate to inappropriate receptor blockade or stimulation, especially in patients with asthma, heart block, or heart failure.

Other names

β1-adrenergic receptorβ2-adrenergic receptorBeta-1 adrenoreceptorBeta-2 adrenoreceptorADRB1ADRB2

Agonist: stimulates receptor, increases cAMP via Gs protein (e.g., bronchodilation, increased cardiac output) Antagonist (beta-blocker): blocks receptor, decreases sympathetic effect (e.g., reduced heart rate, decreased intraocular pressure) Inverse agonist: stabilizes inactive conformation, reduces basal signaling