title: Partial purification of an endogenous inhibitor of muscarinic ligand binding.
abstract: An endogenous inhibitory factor (EIF alpha) to the binding of a muscarinic antagonist, [3H]N-methyl scopolamine ([3H]NMS), has been partially (12-fold) purified from the soluble fraction of the ileal longitudinal muscle of guinea-pigs using a heat-treatment, isoelectric fractionation, and DEAE-column chromatography. The EIF alpha inhibited the [3H]NMS binding to the longitudinal muscle membrane with an IC50 of 53.6 micrograms/ml. This was about 230-fold potent than the non-specific inhibition of [3H]NMS binding by bovine serum albumin (BSA). Zn2+ (0.1 mM) almost completely blocked the inhibitory activity of EIF alpha, whereas such the effect of Zn2+ was not observed in the inhibition by BSA. These results suggest that EIF alpha inhibits the [3H]NMS binding to the muscarinic acetylcholine receptor in a different manner from non-specific interaction with the receptor.
authors.affiliation: Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
authors.forename: Y I
authors.initials: YI
authors.lastname: Fang
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Momose
mesh_terms: D000818:Animals; D001685:Biological Factors / Q000302:isolation & purification*; D006168:Guinea Pigs; D006358:Hot Temperature; D018727:Muscarinic Antagonists / Q000302:isolation & purification*; D009124:Muscle Proteins / Q000302:isolation & purification*; D019832:N-Methylscopolamine; D012602:Scopolamine Derivatives / Q000378:metabolism*
chemical_list: D001685:Biological Factors; D018727:Muscarinic Antagonists; D009124:Muscle Proteins; D012602:Scopolamine Derivatives; D019832:N-Methylscopolamine