title: Complex ionic control of [3H]GBR 12783 binding to the dopamine neuronal carrier.
abstract: At 20 degrees C, [3H]GBR 12783, {1-[2-(diphenylmethoxy)ethyl]4-(3-phenyl-2-([1-3H]propenyl)-pip era zine} dissociated from the dopamine neuronal carrier present in rat striatal membranes with a t1/2 value of 27 min. At this temperature, KCI, CaCl2 and MgCl2 increased the binding dissociation, revealing that they recognize a binding site which is not mutually exclusive with that of [3H]GBR 12783. The comparison of the ability of KCl to increase the binding dissociation (by 160% at 30 mM KCl) with its potency as a binding inhibitor (Ki-2.6 +/- 0.3 mM) suggests an involvement of two recognition sites for K+ in binding inhibition, a not mutually exclusive site and another, mutually exclusive, site. Divalent cations mainly inhibited the binding via a mutually exclusive site since 3 mM Ca2+ and 10 mM Mg2+ increased the binding dissociation by 90% at 20 degrees C whereas their Ki values were 0.049 +/- 0.006 and 0.141 +/- 0.035 mM, respectively. Involvement of this mutually exclusive site was also supported by the persistence of the binding inhibition elicited by Ca2+ and Mg2+ at 0 degree C, a temperature at which they reduced the binding dissociation. At 20 degrees C, 100 mM NaCl did not modify [3H]GBR 12783 binding but it antagonized the binding dissociation elicited by inhibitory cations. Ca2+ reduced the off-rate of [3H]GBR 12783 binding at 0 degree C and in the presence of 100 mM Na+. Finally, [3H]GBR 12783-binding dissociation was increased by high 'cytosolic' K+ while 'synaptic' concentrations of Na+, K+, Ca2+, Mg2+ and Cl- were ineffective. A reduction of H2PO4-/HCO3- from 10 to 5 mM and a substitution of 5 mM H2PO4-/HCO3- by 5 mM Cl- increased the binding dissociation, suggesting that an anion-binding site could also regulate the binding.
authors.affiliation: URA 1969, CNRS, UFR de Médecine et Pharmacle, Saint Etienne du Rouvray, France. p4
authors.forename: C
authors.initials: C
authors.lastname: Héron
authors.forename: G
authors.initials: G
authors.lastname: Billaud
authors.forename: J
authors.initials: J
authors.lastname: Costentin
authors.forename: J J
authors.initials: JJ
authors.lastname: Bonnet
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D010879:Piperazines / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature
chemical_list: D002352:Carrier Proteins; D002412:Cations; D002712:Chlorides; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D010879:Piperazines; C039737:1-(2-(diphenylmethoxy)ethyl)-4-(3-phenyl-2-propenyl)piperazine; D004298:Dopamine