Abstract |
A dimeric pentapeptide enkephalin ( DPE2) consisting of two molecules of [D-Ala 2, Leu 5] enkephalin linked at C-terminal leucine with ethylenediamine, (H-Tyr-D-Ala-Gly-Phe-Leu-NH-Ch2)2 is a bivalent ligand for the delta enkephalin receptors of rat brain and neuroblastoma- glioma hybrid (NG108-15) cells. This new enkephalin analog shows dramatically increased affinity in radioligand assays using whole brain membranes when delta but not mu specific radioligands are employed. When membranes from NG108-15 cells are used, the dimer shows greatly increased activity irrespective of the mu or delta specificity of the tracer. The dimer DPE2 shows a four-fold, " sodium shift" in its IC50 for competition with [3H] naloxone, suggestive of agonist behavior. Agonist activity was confirmed by demonstrating that DPE2 inhibits cyclic AMP production in prostaglandin E1 stimulated NG108-15 cells, and by demonstrating very high potency in the mouse vas deferens bioassay. DPE2 binds to the same delta sites as the delta-selective monomer [D-Ala2, D-Leu5] enkephalin, since the two ligands show complete crossdisplacement. Radiolabeled 3H-DPE2 shows a five-fold higher affinity constant, a 2.5-fold higher association rate constant, and a two-fold lower dissociation rate than the monomer. These results are consistent with the hypothesis that the dimeric pentapeptide enkephalin can bridge two delta receptors. This enkephalin dimer provides a valuable new probe of opiate receptors and their organization in cell membranes.
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Authors | T Costa, Y Shimohigashi, S A Krumins, P J Munson, D Rodbard |
Journal | Life sciences
(Life Sci)
Vol. 31
Issue 15
Pg. 1625-32
(Oct 11 1982)
ISSN: 0024-3205 [Print] Netherlands |
PMID | 6292643
(Publication Type: Journal Article)
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Chemical References |
- Receptors, Opioid
- Naloxone
- Manganese
- Enkephalin, Leucine
- Enkephalin, Leucine-2-Alanine
- enkephalinamide-Leu, Ala(2)-aminoethyl dimer-
- Sodium
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Topics |
- Animals
- Binding, Competitive
- Brain
(metabolism)
- Cell Line
- Cell Membrane
(metabolism)
- Enkephalin, Leucine
(analogs & derivatives, metabolism)
- Enkephalin, Leucine-2-Alanine
(analogs & derivatives)
- Hybrid Cells
- Manganese
(pharmacology)
- Naloxone
(metabolism)
- Radioligand Assay
- Rats
- Receptors, Opioid
(analysis, metabolism)
- Sodium
(pharmacology)
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