Intracellular Ca2+ signals in human-derived pancreatic somatostatin-secreting cells (QGP-1N).
Single-cell microfluorimetry techniques have been used to examine the effects of acetylcholine (0.1-100 microM) on the intracellular free calcium ion concentration ([Ca2+]i) in a human-derived pancreatic somatostatin-secreting cell line, QGP-1N. When applied to the bath solution, acetylcholine was found to evoke a marked and rapid increase in [Ca2+]i at all concentrations tested. These responses were either sustained, or associated with the generation of complex patterns of [Ca2+]i transients. Overall, the pattern of response was concentration related. In general, 0.1-10 microM acetylcholine initiated a series of repetitive oscillations in cytoplasmic Ca2+, whilst at higher concentrations the responses consisted of a rapid rise in [Ca2+]i followed by a smaller more sustained increase. Without external Ca2+, 100 microM acetylcholine caused only a transient rise in [Ca2+]i, whereas lower concentrations of the agonist were able to initiate, but not maintain, [Ca2+]i oscillations. Acetylcholine-evoked Ca2+ signals were abolished by atropine (1-10 microM), verapamil (100 microM) and caffeine (20 mM). Nifedipine failed to have any significant effect upon agonist-evoked increases in [Ca2+]i, whilst 50 mM KCl, used to depolarise the cell membrane, only elicited a transient increase in [Ca2+]i. Ryanodine (50-500 nM) and caffeine (1-20 mM) did not increase basal Ca2+ levels, but the Ca(2+)-ATPase inhibitors 2,5-di(tert-butyl)-hydroquinone (TBQ) and thapsigargin both elevated [Ca2+]i levels. These data demonstrate for the first time cytosolic Ca2+ signals in single isolated somatostatin-secreting cells of the pancreas. We have demonstrated that acetylcholine will evoke both Ca2+ influx and Ca2+ mobilisation, and we have partially addressed the subcellular mechanism responsible for these events.
Squires
P E
PE
Department of Biomedical Science, University of Sheffield, Western Bank, UK.
Amiranoff
B
B
Dunne
M J
MJ
D000109:Acetylcholine / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D010179:Pancreas / Q000166:cytology / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D015398:Signal Transduction; D013004:Somatostatin / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D013729:Terpenes; D012433:Ryanodine; D002110:Caffeine; D013004:Somatostatin; D019284:Thapsigargin; D000109:Acetylcholine; D002118:Calcium