Upregulation refers to an increase in the density of beta-adrenoceptors on the surface membranes and is modulated by a multitude of pharmacologic and pathophysiologic factors. Beta-blockers cause subtype-specific upregulation such that nonselective beta-blockers increase the density of both beta1- and beta2-adrenoceptors whereas beta1-selective antagonists upregulate only beta1-adrenoceptors. As a consequence of increased sympathetic tone, cardiac beta-receptors are down-regulated in the failing ventricle and dilated cardiomyopathy. However, in the presence of acute myocardial ischemia there is rapid upregulation of beta-receptors in the presence of elevated circulating catecholamines, which forms the basis of beta blockade therapy for treatment of ACS.
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