Betaadrenergisiin

Betaadrenergisiin (beta-adrenergic) refers to the family of beta-adrenergic receptors, a subset of adrenergic receptors that mediate the actions of catecholamines such as epinephrine and norepinephrine. These receptors are G protein-coupled receptors that predominantly couple to the stimulatory G protein (Gs). Activation increases adenylate cyclase activity, raises intracellular cAMP, and activates PKA, producing tissue-specific responses.

There are three classical subtypes: β1, β2, and β3. β1 receptors are mainly in the heart and kidneys, increasing heart rate and contractility, and renin release. β2 receptors are abundant in smooth muscle and liver, mediating bronchodilation, vasodilation, glycogenolysis, and smooth muscle relaxation. β3 receptors are primarily in adipose tissue, promoting lipolysis, and are also found in the bladder detrusor muscle, affecting storage and voiding reflexes.

Pharmacology: agonists selectively targeting β1 (e.g., dobutamine) or β2 (e.g., salbutamol) receptors are used to treat heart failure and asthma/COPD, respectively. Nonselective β-agonists (e.g., isoproterenol) have broader effects. Antagonists (beta blockers) inhibit β receptors and are used for hypertension, angina, and arrhythmias; cardioselective agents (e.g., metoprolol) preferentially block β1, reducing cardiac risk with fewer pulmonary side effects. Nonselective blockers (e.g., propranolol) block both β1 and β2.

Clinical note: β-adrenergic signaling influences metabolic rate, lipolysis, and glucose homeostasis; excessive stimulation can contribute to arrhythmias, tremor, and bronchoconstriction in susceptible individuals. The concept of beta-adrenergic receptors has been central to cardiovascular and pulmonary pharmacotherapy.