title: Muscarinic and purinergic Ca2+ mobilizations in the neural retina of early embryonic chick.
abstract: Acetylcholine and adenosine triphosphate (ATP) raise intracellular Ca2+ concentration via muscarinic receptors and P2U purinoceptors by releasing Ca2+ from intracellular Ca2+ stores in the neural retina of early embryonic chick. The signal transduction mechanisms for the muscarinic and purinergic Ca2+ responses were studied with fura-2 fluorescence measurements. Li+ (1 mM), which inhibits phosphatidylinositol metabolism, enhanced both the Ca2+ rises to carbamylcholine (CCh. 30 microM) a muscarinic agonist and ATP (200 microM). Thapsigargin (250 nM), an inhibitor of Ca(2+)-ATPase of inositol trisphosphate (IP3)-sensitive Ca2+ stores, abolished both the Ca2+ rises to CCh (100 microM) and ATP (500 microM). U-73122 (2 microM), an inhibitor of phospholipase C beta, suppressed the Ca2+ rise to ATP (500 microM), but its analog U-73343 (2 microM) did not suppress it. In contrast, both U-73122 and U-73343 suppressed the Ca2+ the Ca2+ rise to CCh (100 microM). Pertussis toxin (250 ng/ml) suppressed the ATP-induced Ca2+ rise at least partly, whereas no inhibition was observed on the CCh-induced Ca2+ rise. Cross-talk occurred between the muscarinic and purinergic Ca2+ mobilizations but they were not occlusive. This study suggests that the muscarinic and purinergic Ca2+ mobilizations utilize IP3-sensitive Ca2+, stores, but different signal transduction pathways are involved in between the muscarinic and purinergic Ca2+ responses.
authors.affiliation: Department of Physiology, Osaka University Medical School, Suita, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Sakaki
authors.forename: Y
authors.initials: Y
authors.lastname: Fukuda
authors.forename: M
authors.initials: M
authors.lastname: Yamashita
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002642:Chick Embryo; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000187:drug effects; D008094:Lithium / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D009474:Neurons / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D037342:Pertussis Toxin; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D058913:Purinergic Agonists; D011760:Pyrrolidinones / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000378:metabolism*; D011983:Receptors, Purinergic / Q000378:metabolism*; D012160:Retina / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019284:Thapsigargin / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D004963:Estrenes; D018721:Muscarinic Agonists; D010726:Phosphodiesterase Inhibitors; D058913:Purinergic Agonists; D011760:Pyrrolidinones; D011976:Receptors, Muscarinic; D011983:Receptors, Purinergic; D010566:Virulence Factors, Bordetella; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C074854:U 73343; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D002217:Carbachol; D008094:Lithium; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000109:Acetylcholine; D002118:Calcium