High affinity quinuclidinyl benzilate binding to rat parotid membranes requires muscarinic receptor. G protein interactions.
The binding of the non-selective muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) to rat parotid membranes was characterized. Under equilibrium conditions, [3H]QNB bound to a homogenous population of muscarinic receptors (Kd, 118 +/- 19 pM; Bmax, 572 +/- 42 fmol/mg membrane protein, n = 12). The addition of G protein activators AlF4- or guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) + Mg2+ increased the Kd by 77 +/- 7% (n = 4, P less than 0.05) and 83 +/- 27% (n = 7, P less than 0.05), respectively, without a change in the Bmax or homogeneity of the binding site. GTP gamma S added without exogenous Mg2+ did not affect [3H]QNB binding. Thus, optimal QNB binding requires a muscarinic receptor/G protein interaction.
Horn
V J
VJ
Clinical Investigations and Patient Care Branch, National Institute of Dental Research, NIH, Bethesda, MD 20892.
Ambudkar
I S
IS
Baum
B J
BJ
D000535:Aluminum / Q000494:pharmacology; D017607:Aluminum Compounds; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D010306:Parotid Gland / Q000378:metabolism*; D011813:Quinuclidinyl Benzilate / Q000378:metabolism*; D051381:Rats; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology
D017607:Aluminum Compounds; D011976:Receptors, Muscarinic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011813:Quinuclidinyl Benzilate; D012969:Sodium Fluoride; D000535:Aluminum; D019204:GTP-Binding Proteins; D008274:Magnesium; D005459:Fluorides; C032311:aluminum fluoride