Characterization of rat cerebral cortical beta adrenoceptor subtypes using (-)-( sup 125 I)-iodocyanopindolol

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Journal of Receptor Research; (USA)

OSTI ID:6532386

Tiong, A H; Richardson, J S ^[1]

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1. Univ. of Saskatchewan, Saskatoon (Canada)

(-)-(125I)-Iodocyanopindolol (-(ICYP)), used to characterize beta adrenoceptors on membrane preparations from rat cerebral cortex, was shown to have affinity for both beta adrenoceptors and serotonin receptors. Therefore, 10 microM serotonin was added to the assays to prevent (-)ICYP binding to serotonin receptors. Under these conditions, (-)ICYP binding to the cortical membrane preparation was reversible and saturable, and the association reaction was very slow. The dissociation reaction was also very slow, and revealed two affinity states corresponding to a high and a low affinity state. Scatchard analysis showed a single class of binding sites with an equilibrium dissociation constant (KD) of 20.7 pM, and a maximal density of binding sites (Bmax) of 95.1 fmol/mg membrane protein. Displacement binding analyses revealed a potency series of (-) isoproterenol greater than (-) epinephrine equal to (-) norepinephrine, suggesting a predominance of the beta 1 adrenoceptor subtype. Detailed competition ligand binding studies with the selective beta 1 adrenoceptor antagonist ICI-89406 and the selective beta 2 adrenoceptor antagonist ICI-118551, showed that about 70% of the beta adrenoceptor population in the rat cortex is of the beta 1 subtype with the remainder being of the beta 2 subtype. We conclude that since (-)ICYP binds to both beta adrenoceptors and serotonin receptors, it is important to prevent the binding of (-)ICYP to serotonin receptors by adding a suppressing ligand like excess cold serotonin when assaying beta adrenoceptors. We have presented the first such characterization of rat cerebral cortical beta adrenoceptors with (-)ICYP in this study.

• OSTI ID: 6532386
• Journal Information: Journal of Receptor Research; (USA), Journal Name: Journal of Receptor Research; (USA) Vol. 9:6; ISSN 0197-5110; ISSN JRERD
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CARDIOVASCULAR AGENTS
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CEREBRAL CORTEX
CEREBRUM
CYCLASES
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INDOLES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGANDS
LYASES
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PARASYMPATHOMIMETICS
PROTEINS
PYRROLES
RADIOISOTOPES
RADIOPROTECTIVE SUBSTANCES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SEROTONIN
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRYPTAMINES
VASODILATORS
VERTEBRATES