title: Regulation of [Ca2+]i by secretagogue stimulation of canine gastric parietal cells.
abstract: The ability of gastrin, histamine, and carbachol to stimulate acid secretion by direct action on gastric parietal cells is well established but the role of intracellular Ca2+ concentration ([Ca2+]i) in mediating these effects is the subject of some controversy. To examine this issue further, secretagogue-mediated changes in [Ca2+]i in single isolated canine gastric parietal cells were examined by microspectrofluorometry of fura-2-loaded cells. Resting [Ca2+]i in single parietal cells was 63 +/- 6 (SE) nM. Carbachol, 10(-5) M, induced a maximum elevation in [Ca2+]i with an initial transient rise of 178 +/- 24 (SE) nM, which was maintained in the absence of extracellular Ca2+ and a sustained plateau of 112 +/- 20 (SE) nM, which was abolished by removal of extracellular Ca2+. Both effects were reversed by the muscarinic receptor antagonist atropine. Gastrin (10(-9)-10(-7) M) also induced a bimodal rise in [Ca2+]i with a maximal initial transient rise of 206 +/- 14 nM and a sustained plateau of 94 +/- 9 nM. Both components of the [Ca2+]i response to gastrin were reversed by the gastrin specific antagonist L 365260. Lower concentrations of gastrin (10(-10) M) induced repetitive transient increases (oscillations) in cytosolic Ca2+. The amplitude of the first spike was less than 50% of the transient rise in [Ca2+]i stimulated by 10(-8) M gastrin. The oscillations occurred at a rate of 0.9/min, gradually decreasing in amplitude within 15 min of secretagogue administration. Histamine (10(-4) M) led to a minimal rise in [Ca2+]i (less than 5% of control) in less than 10% of the canine parietal cells tested.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109.
authors.forename: J
authors.initials: J
authors.lastname: Delvalle
authors.forename: Y
authors.initials: Y
authors.lastname: Tsunoda
authors.forename: J A
authors.initials: JA
authors.lastname: Williams
authors.forename: T
authors.initials: T
authors.lastname: Yamada
mesh_terms: D000818:Animals; D001570:Benzodiazepinones / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005755:Gastrins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D010295:Parietal Cells, Gastric / Q000187:drug effects / Q000378:metabolism*; D010671:Phenylurea Compounds; D011817:Rabbits; D015398:Signal Transduction / Q000187:drug effects; D013045:Species Specificity; D013050:Spectrometry, Fluorescence
chemical_list: D001570:Benzodiazepinones; D005755:Gastrins; D010671:Phenylurea Compounds; C058121:L 365260; C013550:gastrin 17; D006632:Histamine; D002217:Carbachol; D002118:Calcium