title: Muscarinic receptors in isolated smooth muscle cells from gastric antrum.
abstract: Smooth muscle cells from the gastric antrum of the rabbit were isolated using collagenase and pronase. We examined the characteristics of muscarinic receptors that control contraction of the muscle cell: kinetics, stoichiometry and specificity of both contractile response to muscarinic agents and binding of labeled N-methyl-scopolamine. Cells contracted in the presence of muscarinic agents after a short time (30 sec) while binding of (3H)-NMS reached a plateau after 10 min exposure. Specific binding was saturable and Scatchard analysis revealed a single class of high-affinity binding sites (Kd: 0.5 nM). Oxotremorine was the most potent agonist with an ED50 of 0.6 pM; acetylcholine and carbachol were 10 times less potent. Muscarinic antagonists competed with (3H)-NMS for binding with IC50 values in the same range (nanomolar or less) than those obtained for inhibition of acetylcholine-induced contractions. Pirenzepine antagonized contractile effect of muscarinic agonists with EC50 in a micromolar range. Intracellular levels of cyclic AMP were lowered by muscarinic agonists. Monoclonal anti-muscarinic receptor antibodies M-35 displayed agonist-like activities triggering contraction and lowering cyclic AMP levels of the cells. However, although the antagonist inhibits M-35-induced contractions and cAMP decrease, M-35 had no effect on binding of the antagonist to the muscarinic receptor. These data revealed the presence of an M2-muscarinic receptor subtype involved in the contractile response of the isolated smooth muscle cell.
authors.affiliation: Laboratoire de Biochimie des Membranes, CNRS ER 228, Faculté de Pharmacie, Montpelier, France.
authors.forename: C
authors.initials: C
authors.lastname: Moummi
authors.forename: R
authors.initials: R
authors.lastname: Magous
authors.forename: D
authors.initials: D
authors.lastname: Strosberg
authors.forename: J P
authors.initials: JP
authors.lastname: Bali
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001285:Atropine / Q000494:pharmacology; D000242:Cyclic AMP / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*; D019832:N-Methylscopolamine; D011706:Pyloric Antrum / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000276:immunology / Q000502:physiology*; D012602:Scopolamine Derivatives / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D001285:Atropine; D000242:Cyclic AMP; D000109:Acetylcholine; D019832:N-Methylscopolamine