An Immortalized Myocyte Cell Line, HL-1, Expresses a Functional δ -Opioid Receptor |
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| Authors: | |
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| Affiliation: | a Department of Cardiac Surgery, University of Michigan, B558 MSRB II, Ann Arbor, MI 48109-0686, USA;b Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans, LA 70112, USA;c Department of Pharmacology, University of Michigan, 1301 MSRB III, Ann Arbor, MI 48109-0632, USA |
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| Abstract: | The present study characterizes opioid receptors in an immortalized myocyte cell line, HL-1. Displacement of [3H]bremazocine by selective ligands for the mu (μ), delta (δ), and kappa (κ) receptors revealed that only the δ -selective ligands could fully displace specific [3H]bremazocine binding, indicating the presence of only the δ -receptor in these cells. Saturation binding studies with the δ -antagonist naltrindole afforded a Bmaxof 32 fmols/mg protein and a KDvalue for [3H]naltrindole of 0.46 n . The binding affinities of variousδ ligands for the receptor in HL-1 cell membranes obtained from competition binding assays were similar to those obtained using membranes from a neuroblastoma×glioma cell line, NG108-15. Finally, various δ -agonists were found to stimulate the binding of [35S]GTP γ S, confirming coupling of the cardiac δ -receptor to G-protein. DADLE (D-Ala-D-Leu-enkephalin) was found to be the most efficacious in this assay, stimulating the binding of [35S]GTP γ S to 27% above basal level. The above results indicate that the HL-1 cell line contains a functionally coupled δ -opioid receptor and therefore provides an in vitro model by which to study the direct effects of opioids on cardiac opioid receptors. |
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| Keywords: | Cardiac myocytes δ -opioid receptor Radioligand binding [35S]GTP γ S binding. |
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