Opioid binding site in EL-4 thymoma cell line.
Using EL-4 thymoma cell-line we found a binding site similar to the k opioid receptor of the nervous system. The Scatchard analysis of the binding of [3H] bremazocine indicated a single site with a KD = 60 +/- 17 nM and Bmax = 2.7 +/- 0.8 pmols/10(6) cells (51 pmols/mg total cell proteins). To characterize this binding site, competition studies were performed using selective compounds for the various opioid receptors. The k agonist U-50,488H was the most potent displacer of [3H] bremazocine with an IC50 value = 0.57 microM. The two stereoisomers levorphanol and dextrorphan showed the same affinity for this site (IC50 = 2.9 microM and 1.9 microM respectively). While morphine, [D-Pen2, D-Pen5] enkephalin and beta-endorphin failed to displace, except at very high concentrations, codeine demonstrated a IC50 = 60 microM, that was similar to naloxone (IC50 = 69 microM).
Fiorica
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Department of Neurosciences, Roche Institute of Molecular Biology, Nutley, New Jersey 07110.
Spector
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D000700:Analgesics / Q000378:metabolism; D000818:Animals; D001575:Benzomorphans / Q000378:metabolism; D001667:Binding, Competitive; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D011957:Receptors, Opioid / Q000378:metabolism*; D013945:Thymoma / Q000378:metabolism*; D013953:Thymus Neoplasms / Q000378:metabolism*
D000700:Analgesics; D001575:Benzomorphans; D011957:Receptors, Opioid; C027248:bremazocine