Alteration of the physicochemical properties of triphosphoinositide by nicotinic ligands.
The concentrations of nicotinic drugs required to effect a 50% transfer of triphosphol[3H]isositide from an aqueous phase to a nonaqueous phase closely approximated their concentrations for both in vivo neuromuscular blocking activity and binding to purified nicotinic receptors, and correlated well (correlation coefficient = 0.95)) with their biological activities measured by other workers in an Electrophorus electroplax preparation. The triphospho[3H]inositide transfer induced by nicotinic ligands was dependent on the lipid concentration and was potentiated by Ca2+. The affinity constants of 45Ca2+ for triphosphoinositide were similar to those for the purified nicotinic receptor. These and other findings suggest the possibility that triphosphoinositide (phosphatidylinositol bisphosphate) is a binding site of the nicotinic receptor.
D001665:Binding Sites; D002118:Calcium; D005731:Ganglionic Stimulants; D007811:Lanthanum; D008024:Ligands; D010716:Phosphatidylinositols; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic
D005731:Ganglionic Stimulants; D008024:Ligands; D010716:Phosphatidylinositols; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; D007811:Lanthanum; D002118:Calcium