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Characterization of rat brain opioid receptors by (Tyr-3,5-/sup 3/H)1, D-Ala2, Leu5-enkephalin binding

Journal Article · · Neurochem. Res.; (United States)
OSTI ID:5220856
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(Tyr-3,5-/sup 3/H)1, D-Ala2, Leu5-enkephalin ((/sup 3/H)DALA) was used for labeling the opioid receptors of rat brain plasma membranes. The labeled ligand was prepared from (Tyr-3,5-diiodo)1, D-Ala2, Leu5-enkephalin by catalytic reductive dehalogenation in the presence of Pd catalyst. The resulting (Tyr-3,5-/sup 3/H)1, D-Ala2, Leu5-enkephalin had a specific activity of 37.3 Ci/mmol. In the binding experiments steady-state level was reached at 24 degrees C within 45 min. The pseudo first order association rate constant was 0.1 min-1. The dissociation of the receptor-ligand complex was biphasic with k-1-s of 0.009 and 0.025 min-1. The existence of two binding sites was proved by equilibrium studies. The high affinity site showed a KD = 0.7 nM and Bmax = 60 fmol/mg protein; the low affinity site had a KD = 5 nM and Bmax = 160 fmol/mg protein. A series of opioid peptides inhibited (/sup 3/H)DALA binding more efficiently than morphine-like drugs suggesting that labeled ligand binds preferentially to the delta subtype of opioid receptors. Modification of the original peptides either at the C or N terminal ends of the molecules resulted in a decrease in their affinity.

Research Organization:
Hungarian Academy of Sciences, Szeged
OSTI ID:
5220856
Journal Information:
Neurochem. Res.; (United States), Journal Name: Neurochem. Res.; (United States) Vol. 5; ISSN NERED
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CHEMICAL BONDS
COMPARATIVE EVALUATIONS
DRUGS
ENDORPHINS
ENKEPHALINS
KINETICS
LABELLED COMPOUNDS
LIGANDS
MAMMALS
MEMBRANES
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANS
PEPTIDES
POLYPEPTIDES
PROTEINS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
TRITIUM COMPOUNDS
VERTEBRATES