Effect of sodium on [3H]ethylketocyclazocine binding to opioid receptors in frog brain membranes |
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Authors: | Sandor Benyhe Tibor Farkas Maria Wollemann |
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Affiliation: | (1) Institute of Biochemistry, Biological Research Center of Hungarian, P.O. Box 521, 6701 Szeged, Hungary;(2) Academy of Sciences, P.O. Box 521, 6701 Szeged, Hungary |
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Abstract: | The specific binding of (3H)ethylketocyclazocine to frog brain membrane preparation was enhanced in the presence of sodium ions administered as NaCl, both at 0 °C and at room temperature. The optimal NaCl concentration was 25 mM at 0 °C and 50 mM at 24 °C. MgCl2 inhibited the [3H]ethylketocyclazocine binding. Two binding sites (high and low affinity) were established with [3H]ethylketocyclazocine as ligand by equilibrium binding studies. Addition of NaCl increased the Bmax of the low-affinity site more than that of the high-affinity site at both temperatures. Affinities were higher at 0 °C than at 24 °C. TheKD values were not significantly influenced by sodium ions. The dissimilarities between the rat and frog brain opioid receptors in [3H]ethylketocyclazocine binding are attributed to the different lipid composition of the two membranes.Abbreviations used DAGO D-Ala2-(Me)Phe4-Gly-ol5-enkephalin - DALE d-Ala2-l-Leu5-enkephalin - DADLE d-Ala2-d-Leu5-enkephalin - EKC Ethylketocyclazocine - DHM Dihydromorphine - BIT 2-(p-ethoxybenzyl)1-diethylaminoethyl-5-isothiocyanobenzimidazole isothiocyanate - FIT Fentanyl isothiocyanate |
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Keywords: | Kappa opioid receptor frog brain sodium ion effect [3H]ethylketocyclazocine binding |
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