title: The effect of strontium on the drug-receptor interaction on cholinergic drugs.
abstract: The effect of replacing calcium with strontium in the perfusion fluid was qualitatively and quantitatively studied in the isolated longitudinal muscle of the guinea-pig ileum. In the presence of strontium hyoscine could be considered a competitive antagonist of acetylcholine for the acetylcholine receptor of the longitudinal muscle of the guinea-pig ileum; dibenamine still blocked this receptor in an irreversible way. The equilibrium constants for acetylcholine (KA) and hyoscine (KI) were obtained in the presence of calcium (KA = 3.16 +/- 0.63 microM; KI = 0.38 +/- 0.07 nM), and strontium (KA = 7.00 +/- 0.89 microM; KI = 0.93 +/- 0.16 nM). The results show a decrease in the affinity of both drugs for the muscarinic receptor in the presence of strontium.
authors.affiliation: Instituto de Farmacologia, Faculdade de Medicina de Lisboa, Portugal.
authors.forename: B
authors.initials: B
authors.lastname: Macara
authors.forename: J M
authors.initials: JM
authors.lastname: Rico
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003983:Dibenzylchlorethamine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D010277:Parasympathomimetics / Q000494:pharmacology*; D011950:Receptors, Cholinergic / Q000187:drug effects* / Q000378:metabolism; D012601:Scopolamine / Q000494:pharmacology; D013324:Strontium / Q000494:pharmacology*
chemical_list: D010277:Parasympathomimetics; D011950:Receptors, Cholinergic; D003983:Dibenzylchlorethamine; D012601:Scopolamine; D000109:Acetylcholine; D002118:Calcium; D013324:Strontium