Biomaterial Database

In vitro characterization of skeletal muscle beta-adrenergic receptors coupled to adenylate cyclase. 1979

N B Reddy, and W K Engel

[3H]Dihydroalprenolol, a potent beta-adrenergic antagonist, was used to identify the adenylate cyclase-coupled beta-adrenoceptors in isolated membranes of rat skeletal muscle. The receptor sites, as revealed by [3H]dihydroalprenolol binding, were predominantly localized in plasmalemmal fraction. That skeletal muscle fraction may also contain the plasmalemma of other intramuscular cells, especially that of blood vessels. Hence, the [3H]dihydroalprenolol binding observed in that fraction may be due partly to its binding to the plasmalemma of blood vessels. Small but consistent binding was also observed in sarcoplasmic reticulum and mitochondria. The level of [3H]dihydroalprenolol binding in different subcellular fractions closely correlated with the level of adenylate cyclase present in those fractions. The binding of [3H]dihydroalprenolol to plasmalemma exhibited saturation kinetics. The binding was rapid, reaching equilibrium within 5 min, and it was readily dissociable. From the kinetics of binding, association (K1) and dissociation (K2) rate constants of 2.21 . 10(7) M-1 . min-1 and 3.21 . 10(-1) min-1, respectively, were obtained. The dissociation constant (Kd) of 15 mM for [3H]dihydroalprenolol obtained from saturation binding data closely agreed with the Kd derived from the ratio of dissociation and association rate constants (K2/K1). Several beta-adrenergic agents known to be active on intact skeletal muscle also competed for [3H]dihydroalprenolol binding sites in isolated plasmalemma with essentially similar selectivity and stereospecificity. Catecholamines competed for [3H]dihydroalprenolol binding sites with a potency of isoproterenol greater than epinephrine greater than norepinephrine. A similar order of potency was noted for catecholamines in the activation of adenylate cyclase. Effects of catecholamines were stereospecific, (-)-isomers being more potent than (+)-isomers. Phenylephrine, an alpha-adrenergic agonist, showed no effect either on [3H]dihydroalprenolol binding or on adenylate cyclase. Known beta-adrenergic antagonists, propranolol and alprenolol, stereospecifically inhibited the [3H]dihydroalprenolol binding and the isoproterenol-stimulated adenylate cyclase. The Ki values for the antagonists determined from inhibition of [3H]dihydroalprenolol binding agreed closely with the Ki values obtained from the inhibition of adenylate cyclase. The data suggest that the binding of [3H]dihydroalprenolol in skeletal muscle membranes possess the characteristics of a substance binding to the beta-adrenergic receptor.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008297	Male		Males
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011941	Receptors, Adrenergic	Cell-surface proteins that bind epinephrine and/or norepinephrine with high affinity and trigger intracellular changes. The two major classes of adrenergic receptors, alpha and beta, were originally discriminated based on their cellular actions but now are distinguished by their relative affinity for characteristic synthetic ligands. Adrenergic receptors may also be classified according to the subtypes of G-proteins with which they bind; this scheme does not respect the alpha-beta distinction.	Adrenergic Receptors,Adrenoceptor,Adrenoceptors,Norepinephrine Receptor,Receptors, Epinephrine,Receptors, Norepinephrine,Adrenergic Receptor,Epinephrine Receptors,Norepinephrine Receptors,Receptor, Adrenergic,Receptor, Norepinephrine
D011943	Receptors, Adrenergic, beta	One of two major pharmacologically defined classes of adrenergic receptors. The beta adrenergic receptors play an important role in regulating CARDIAC MUSCLE contraction, SMOOTH MUSCLE relaxation, and GLYCOGENOLYSIS.	Adrenergic beta-Receptor,Adrenergic beta-Receptors,Receptors, beta-Adrenergic,beta Adrenergic Receptor,beta-Adrenergic Receptor,beta-Adrenergic Receptors,Receptor, Adrenergic, beta,Adrenergic Receptor, beta,Adrenergic beta Receptor,Adrenergic beta Receptors,Receptor, beta Adrenergic,Receptor, beta-Adrenergic,Receptors, beta Adrenergic,beta Adrenergic Receptors,beta-Receptor, Adrenergic,beta-Receptors, Adrenergic
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D004082	Dihydroalprenolol	Hydrogenated alprenolol derivative where the extra hydrogens are often tritiated. This radiolabeled form of ALPRENOLOL, a beta-adrenergic blocker, is used to label the beta-adrenergic receptor for isolation and study.	1-((Methylethyl)amino)-3-(2-propylphenoxy)-2-propanol
D000262	Adenylyl Cyclases	Enzymes of the lyase class that catalyze the formation of CYCLIC AMP and pyrophosphate from ATP.	Adenyl Cyclase,Adenylate Cyclase,3',5'-cyclic AMP Synthetase,Adenylyl Cyclase,3',5' cyclic AMP Synthetase,AMP Synthetase, 3',5'-cyclic,Cyclase, Adenyl,Cyclase, Adenylate,Cyclase, Adenylyl,Cyclases, Adenylyl,Synthetase, 3',5'-cyclic AMP
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia