Lack of [3H]quinuclidinyl benzylate binding to biologically relevant binding sites on mononuclear cells.
We analyzed the binding characteristics of [3H]quinuclidinyl benzylate ([3H]QNB), a muscarinic cholinergic ligand, to rat and human mononuclear cells (MNC). Under various assay conditions, atropine-sensitive, saturable binding occurred with an apparent Kd of 10 nM. Conditions which disrupted the MNC membrane reduced total binding and eliminated specific binding. Muscarinic agonists were unable to inhibit [3H]QNB binding to MNC at concentrations up to 10(-2) M. Stereoisomers dexetimide and levetimide were equipotent inhibitors of binding (IC50 2 x 10(-5) M). We conclude that, although atropine-sensitive binding of [3H]QNB to MNC occurs, the binding is not consistent with the presence of a biologically relevant muscarinic cholinergic receptor.
Adams
E M
EM
Research Service, Hines V.A. Hospital, Illinois 60141.
Lubrano
T M
TM
Gordon
J
J
Fields
J Z
JZ
D000328:Adult; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D002738:Chloroquine / Q000378:metabolism; D006801:Humans; D007461:Iodoacetates / Q000378:metabolism; D019807:Iodoacetic Acid; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D010276:Parasympatholytics / Q000378:metabolism; D010277:Parasympathomimetics / Q000378:metabolism; D011813:Quinuclidinyl Benzilate / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013045:Species Specificity
D007461:Iodoacetates; D010276:Parasympatholytics; D010277:Parasympathomimetics; D011976:Receptors, Muscarinic; C028484:quinuclidinyl benzilate receptor; D011813:Quinuclidinyl Benzilate; D002738:Chloroquine; D019807:Iodoacetic Acid