title: Muscarinic acetylcholine receptor-mediated phosphoinositide turnover in cultured human retinal pigment epithelium cells.
abstract: Cultured retinal pigment epithelium cells prepared from post-mortem adult human eyes are shown to contain muscarinic receptors associated with phosphoinositide turnover. Carbachol at a concentration of 100 microM induced a four-fold increase in 3H-inositol phosphates (more than 76% is in the form of 3H-inositol-1-phosphate) accumulation within 45 min in cells prelabelled with 3H-myoinositol and exposed to 5 mM LiCl. The EC50 of carbachol was approx. 70 microM and the saturation concentration was about 1 mM. The carbachol-induced response was blocked by both atropine and pirenzepine, the former being most effective. Pre-exposure of cells to carbachol resulted in desensitization and a drastic reduction in the subsequent carbachol-induced stimulation of 3H-inositol phosphates. The carbachol response could be attenuated by the biologically active phorbol ester, 4 beta-phorbol 12-myristate 13-acetate, and this was nullified by the protein kinase C inhibitor, staurosporine. The biologically inactive phorbol ester, 4 alpha-phorbol 12,13 dideconoate, did not attenuate the carbachol-induced stimulation of 3H-inositol phosphates. Pertussis toxin failed to influence the carbachol receptor-mediated phosphoinositide turnover. These studies provide clear evidence for the occurrence of muscarinic receptors coupled to phosphoinositide hydrolysis on human retinal pigment epithelium cells.
authors.affiliation: Nuffield Laboratory of Ophthalmology, University of Oxford, U.K.
authors.forename: N N
authors.initials: NN
authors.lastname: Osborne
authors.forename: F
authors.initials: F
authors.lastname: FitzGibbon
authors.forename: G
authors.initials: G
authors.lastname: Schwartz
mesh_terms: D000328:Adult; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D037342:Pertussis Toxin; D010716:Phosphatidylinositols / Q000378:metabolism*; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D010890:Pirenzepine / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013268:Stimulation, Chemical; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D011976:Receptors, Muscarinic; D010566:Virulence Factors, Bordetella; D010890:Pirenzepine; D001285:Atropine; D002217:Carbachol; D037342:Pertussis Toxin; D013755:Tetradecanoylphorbol Acetate