An Immortalized Myocyte Cell Line, HL-1, Expresses a Functional δ -Opioid Receptor

• Published in: Journal of molecular and cellular cardiology Vol. 32; no. 12; pp. 2187 - 2193
• Main Authors: Neilan, Claire L., Kenyon, Erin, Kovach, Melissa A., Bowden, Kristin, Claycomb, William C., Traynor, John R., Bolling, Steven F.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-12-2000
• Subjects: [35S]GTP γ S binding; Analgesics - pharmacology; Benzomorphans - pharmacology; Binding, Competitive; Cardiac myocytes; Cell Line; Cells, Cultured; Dose-Response Relationship, Drug; Enkephalin, Leucine-2-Alanine - pharmacology; Guanosine 5'-O-(3-Thiotriphosphate) - metabolism; Kinetics; Ligands; Myocardium - cytology; Myocardium - metabolism; Naltrexone - analogs & derivatives; Naltrexone - pharmacology; Narcotic Antagonists - pharmacology; Radioligand binding; Receptors, Opioid, delta - antagonists & inhibitors; Receptors, Opioid, delta - biosynthesis; Time Factors; Tumor Cells, Cultured; δ -opioid receptor; [35S]GTP γ S binding; δ -opioid receptor; Radioligand binding; Cardiac myocytes
• ISSN: 0022-2828; 1095-8584
• DOI: 10.1006/jmcc.2000.1241

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 M. 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.