The β-Adrenergic Receptors and Their Mode of Interaction with Adenylate Cyclase
The classification into α- and β-receptors has been extended in recent years as a result of extensive detailed studies of structure-activity relationships; thus, β-adrenergic responses can be divided into two subclasses: βl and β2. Epinephrine and norepinephrine are approximately equipotent agonists for β1-receptors which are preferentially blocked by practolol. Epinephrine is more potent than norepinephrine in activating β2-receptors which are inhibited by butoxamine. A variety of antagonists such as propranolol, alprenolol and pindolol inhibit the catecholamine response of both βl- and β2-receptors. βl and β2 are functionally similar as both of them are coupled to and activate the enzyme adenylate cyclase as the signal system, and will therefore be discussed as a single family of β-receptors.
KeywordsAdenylate Cyclase Cyclase Activation Affinity Label Catecholamine Receptor Guanyl Nucleotide
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