Negative cooperativity among beta-adrenergic receptors in frog erythrocyte membranes. 1976

L E Limbird, and R J Lefkowitz

(-)-[3H]Dihydroalprenolol, a potent competitive beta-adrenergic antagonist, has been previously documented to bind to the adenylate cyclase-coupled beta-adrenergic receptor sites in mammalian and non-mammalian tissues. Steady state binding of (-)-[3H]dihydroalprenolol to sites in frog erythrocyte membranes, a model system for adenylate cyclase-coupled beta-adrenergic receptors, displays characteristics consistent with negative cooperativity among the beta-adrenergic receptors: Scatchard plots are curvilinear with upward concavity and slopes of Hill plots are consistently less than 1.0. The existence of site-site interactions of the negatively cooperative type were demonstrated directly by the ability of unlabeled (-)-alprenolol to accelerate the dissociation of (-)-[3H]dihydroalprenolol under conditions were no rebinding of radioligand occurred. The dissociation rate of (-)-[3H]dihydroalprenolol alone is directly related to temperature and increases with increases in temperature from 4-37 degrees. (-)-[3H]Dihydroalprenolol dissociation is enhanced by unlabeled (-)-alprenolol at all temperatures studied; however, at 4 degrees, the time required to observe an enhancement of radioligand dissociated is greater than the time required for unlabeled (-)-alprenolol to occupy the empty receptor sites, suggesting that increased rigidity of the biomembrane at 4 degrees may be responsible for the absence of readily observable site-site interactions. The ability of a number of beta-adrenergic agonists and antagonists to induce negative cooperativity among the beta-adrenergic receptors was directly related to their affinity for the receptor sites rather than their intrinsic activity in the adenylate cyclase-coupled beta-adrenergic system. The ability to induce site-site interactions among the beta-adrenergic receptors occurs at physiological concentrations of beta-adrenergic agents, since occupancy of less than 10% of the receptor sites is sufficient to reduce receptor affinity. Changes in pH from 6.5 to 9.0 did not significantly alter the negatively cooperative site-site interactions among the receptor sites. The negatively cooperative phenomenon was also independent of Mg2+, Ca2+, and NaF concentrations in the buffer medium. The presence of guanyl-5'-yl imidodiphosphate, a nonhydrolyzable nucleotide analog which enhances adenylate cyclase stimulation (Vmax) by beta-adrenergic agonists and decreases the concentration of agonist required to half-maximally stimulate adenylate cyclase, did not alter the ability of either agonists or antagonists to induce negatively cooperative site-site interactions among the beta-adrenergic receptors.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D009638 Norepinephrine Precursor of epinephrine that is secreted by the ADRENAL MEDULLA and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the LOCUS CERULEUS. It is also found in plants and is used pharmacologically as a sympathomimetic. Levarterenol,Levonorepinephrine,Noradrenaline,Arterenol,Levonor,Levophed,Levophed Bitartrate,Noradrenaline Bitartrate,Noradrénaline tartrate renaudin,Norepinephrin d-Tartrate (1:1),Norepinephrine Bitartrate,Norepinephrine Hydrochloride,Norepinephrine Hydrochloride, (+)-Isomer,Norepinephrine Hydrochloride, (+,-)-Isomer,Norepinephrine d-Tartrate (1:1),Norepinephrine l-Tartrate (1:1),Norepinephrine l-Tartrate (1:1), (+,-)-Isomer,Norepinephrine l-Tartrate (1:1), Monohydrate,Norepinephrine l-Tartrate (1:1), Monohydrate, (+)-Isomer,Norepinephrine l-Tartrate (1:2),Norepinephrine l-Tartrate, (+)-Isomer,Norepinephrine, (+)-Isomer,Norepinephrine, (+,-)-Isomer
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
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
D004837 Epinephrine The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS. Adrenaline,4-(1-Hydroxy-2-(methylamino)ethyl)-1,2-benzenediol,Adrenaline Acid Tartrate,Adrenaline Bitartrate,Adrenaline Hydrochloride,Epifrin,Epinephrine Acetate,Epinephrine Bitartrate,Epinephrine Hydrochloride,Epinephrine Hydrogen Tartrate,Epitrate,Lyophrin,Medihaler-Epi,Acetate, Epinephrine
D004912 Erythrocytes Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN. Blood Cells, Red,Blood Corpuscles, Red,Red Blood Cells,Red Blood Corpuscles,Blood Cell, Red,Blood Corpuscle, Red,Erythrocyte,Red Blood Cell,Red Blood Corpuscle
D000526 Alprenolol One of the ADRENERGIC BETA-ANTAGONISTS used as an antihypertensive, anti-anginal, and anti-arrhythmic agent. 1-(o-Allylphenoxy)-3-(isopropylamino)-2-propanol,Alfeprol,Alpheprol,Alprenolol Hydrochloride,Aptin,Aptin-Duriles,Aptina,Aptine,H-56-28,Aptin Duriles,AptinDuriles,H 56 28,H5628
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
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D001667 Binding, Competitive The interaction of two or more substrates or ligands with the same binding site. The displacement of one by the other is used in quantitative and selective affinity measurements. Competitive Binding

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