title: Muscarinic M2-receptors enhance polyphosphoinositol release in rat gastric mucosal cells.
abstract: Muscarinic receptor types and their effects on the inositol phosphate second messenger system were studied in enzymatically dispersed rat gastric mucosal cells. Radioreceptor binding studies indicated the presence of a single class of binding sites (4860 +/- 875 sites/cell) and affinities of 0.42 +/- 0.12 nM, 176 +/- 32 nM and 13 microM for N-methylscopolamine, pirenzepine and carbachol, respectively. In cells prelabelled with myo-[3H]inositol carbachol induced a dose-dependent increase in inositol-1-phosphate in the presence of lithium with an ED50 of 10 microM which was antagonized by atropine and pirenzepine (IC50 9 and 700 nM, respectively). Carbachol stimulated amino[14C]pyrine uptake, used as a measure of acid secretion, with an ED50 of 10 microM. The good correlation between these responses suggests a role for inositol phosphates in the muscarinic M2-receptor mediated acid secretion.
mesh_terms: D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001570:Benzodiazepinones / Q000494:pharmacology; D001667:Binding, Competitive; D002217:Carbachol / Q000494:pharmacology; D004357:Drug Synergism; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D010890:Pirenzepine; D051381:Rats; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D013403:Sugar Phosphates / Q000378:metabolism*
chemical_list: D001570:Benzodiazepinones; D007295:Inositol Phosphates; D011976:Receptors, Muscarinic; D013403:Sugar Phosphates; D000632:Aminopyrine; D010890:Pirenzepine; D001285:Atropine; D002217:Carbachol