Effect of sodium on [3H]ethylketocyclazocine binding to opioid receptors in frog brain membranes.
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 degree C and at room temperature. The optimal NaCl concentration was 25 mM at 0 degree C and 50 mM at 24 degrees 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 degree C than at 24 degrees C. The KD 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.
Benyhe
S
S
Institute of Biochemistry, Szeged, Hungary.
Farkas
T
T
Wollemann
M
M
D000818:Animals; D001921:Brain / Q000378:metabolism*; D003496:Cyclazocine / Q000031:analogs & derivatives* / Q000378:metabolism; D016314:Ethylketocyclazocine; D011898:Ranidae; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*; D013347:Subcellular Fractions / Q000378:metabolism; D013696:Temperature
D011957:Receptors, Opioid; D016314:Ethylketocyclazocine; D012964:Sodium; D003496:Cyclazocine