Binding of specific ligands to muscarinic receptors alters the fluidity of membrane fragments from rat brain. A fluorescence polarization study with lipid-specific probes.
The previously suggested method of following ligand-receptor interactions by measuring ligand-induced changes in membrane fluidity [(1986) FEBS Lett. 194, 313-316] was employed to study the binding of specific ligands of the muscarinic receptor to rat brain membrane fragments containing a fluorescent analogue of phosphatidylcholine (APC) as a membrane probe. Upon addition of carbachol and atropine in low concentrations the fluorescence polarization of the APC-labeled membranes decreased significantly demonstrating that binding of these ligands to the muscarinic receptor increases the fluidity of its lipid environment. The fluidity changes were specific, concentration-dependent and saturable. In comparison with radioligand assays the fluorescent lipid probe method proved to be much more sensitive but the Kd values obtained by the two methods differed considerably.
Manevich
E M
EM
Tartu State University, Estonian SSR.
Köiv
A
A
Järv
J
J
Molotkovsky
J G
JG
Bergelson
L D
LD
D000818:Animals; D001285:Atropine / Q000378:metabolism*; D002217:Carbachol / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism* / Q000648:ultrastructure; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D008024:Ligands; D008560:Membrane Fluidity; D051381:Rats; D011976:Receptors, Muscarinic / Q000378:metabolism*
D005456:Fluorescent Dyes; D008024:Ligands; D011976:Receptors, Muscarinic; D001285:Atropine; D002217:Carbachol