Abstract
Barium currents flowing through single Ca2+ channels were recorded from outside-out patches isolated from mouse pancreatic B-cells. Only one type of Ca2+ channel was observed. In 110 mM Ba2+, the single channel conductance was 24 pS (at negative membrane potentials) and the current amplitude at 0 mV was−0.7 pA. Channel openings were activated by depolarisations more positive than −30 mV and showed little inactivation during 200 ms pulses. Open times were increased by BAY K 8644 an decreased by micromolar Cd2+. Channel activity was subject to rundown in excised patches and little activity remained after 10 min. These properties resemble those of L-type Ca2+ channels in other tissues. It is suggested that this Ca2+ channel participates in the generation of the B-cell action potential and mediates the increase in Ca2+ influx required for insulin secretion.
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References
Almers W, McCleskey EW (1984) Non-selective conductance in calcium channels in frog muscle: calcium selectivity in a single file pore. J Physiol 353: 586–608
Armstrong D, Eckert R (1987) Voltage-activated calcium channels that must be phosphorylated to respond to membrane depolarisation. Proc Natl Acad Sci USA 84: 2518–2522
Ashcroft FM, Ashcroft SJH, Harrison DE (1987) Effects of 2-ketoisocaproate on the insulin release and single channel activity in dispersed rat pancreatic β-cells. J Physiol 385: 517–529
Atwater I, Dawson CM, Eddlestone GT, Rojas E (1981) Voltage noise measurements across the pancreatic b-cell membrane: calcium channel characteristics. J Physiol 314: 195–212
Carbone E, Lux HD (1984) A low voltage-activated fully inactivating Ca channel in vertebrate sensory neurons. Nature 310: 501–502
Cook DL, Hales N (1984) Intracellular ATP directly blocks K+ channels in pancreatic B-cells. Nature 311: 271–273
Fenwick EM, Marty A, Neher E (1982) Sodium and calcium channels in bovine chromaffin cells. J Physiol 331: 599–635
Fernandez JM, Fox AP, Krasne S (1984) Membrane patches and whole-cell membranes: a comparison of electrical properties in rat clonal pituitary (GH3) cells. J Physiol 356: 565–585
Findlay I, Dunne MJ (1985) Voltage activated Ca2+ currents in insulin secreting cells. FEBS Lett 189: 281–285
Flockerzi V, Oeken HJ, Hoffman F, Pelzer D, Cavalie A, Trautwein W (1986) Purified dihydropyridine-binding site from skeletal t-tubules is a functional calcium channel. Nature 323: 66–68
Fox AP, Nowycky MC, Tsien RW (1987) Single-channel recordings of three type of calcium channels in chick sensory neurones. J Physiol 394: 173–200
Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ (1981) Improved patch clamp techniques for high resolution current recordings from cells and cell-free membrane patches. Pflügers Arch 391: 85–100
Hellman B, Gylfe E (1986) Calcium and the control of insulin secretion. In: Cheung WY (ed) Calcium and cell function, vol VI. Academic Press Inc, Orlando, FL, pp 253–326
Hess P, Tsien RW (1984) Mechanism of ion permeation through calcium channels. Nature 309: 453–456
Hess P, Lansman JB, Tsien RW (1984) Different modes of Ca channel gating behaviour favoured by dihydropyridine Ca agonists and antagonists. Nature 311: 538–544
Lansman JB, Hess P, Tsien RW (1986) Blockade of current through single calcium channels Cd2+, Mg2+, and Ca2+. J Gen Physiol 88: 321–347
Malaisse-Lagae F, Mathias PCF, Malaisse WJ (1984) Gating and blocking of calcium channels by dihydropyridines in the pancreatic B-cell. Biophys Biochem Res Commun 123: 1062–1068
Matteson DR, Matschinsky FM (1986) Identification of several types of voltage and/or Ca activated channels in a pancreatic β-cell line. Biophys J 49: 432a
McCleskey EW, Fox AP, Feldman D, Tsien RW (1986) Different types of calcium channels. J Exp Biol 124: 177–190
McDonald TF, Cavalie A, Trautwein W, Pelzer D (1986) Voltage-dependent properties of macroscopic and elementary calcium channel currents in guinea-pig ventricular myocytes. Pflügers Arch 406: 437–448
Nowycky MC, Fox AP, Tsien RW (1985) Three type of neuronal calcium channel with different calcium agonist sensitivity. Nature 316: 440–443
Ozawa O, Sand O (1986) Electrophysiology of excitable endocrine cells. Physiol Rev 66: 887–952
Petersen OH, Findlay I (1987) Electrophysiology of the pancreas. Physiol Rev 67: 1054–1116
Plant TD (1987) Calcium current inactivation in cultured mouse pancreatic islet cells is calcium-dependent. J Physiol 390:86P
Prentki M, Matschinsky FM (1987) Ca2+, cAMP, and phospholipid-derived messengers in coupling mechanisms of insulin secretion. Physiol Rev 67: 1185–1249
Ribalet B, Beigelman PM (1981) Effects of divalent cations on β-cell electrical activity. Am J Physiol 241: C59-C67
Rorsman P (1988) Two types of calcium currents with different sensitivities to organic Ca2+ channel antagonists in guinea pig. J Gen Physiol 91: 243–254
Rorsman P, Trube G (1986) Calcium and delayed potassium currents in mouse pancreatic β-cells under voltage clamp conditions. J Physiol 374: 531–550
Rorsman P, Arkhammar P, Berggren PO (1986) Voltage-activated Na+ currents and their suppression by phorbol ester in clonal insulin-producing RINm5F cells. Am J Physiol 251: c912-c919
Sanguinetti MC, Krafte DS, Kass RS (1986) Voltage-dependent modulation of Ca channel current in heart cells by Bay K 8644. J Gen Physiol 88: 369–392
Satin LS, Cook DL (1985) Voltage gated Ca2+ current in pancreatic B-cells. Pflügers Arch 404: 385–387
Satin LS, Cook DL (1986) Voltage-gated Ca current in pancreatic islet b-cells. In: Atwater I, Rojas E, Sorias B (eds) Biophysics of the pancreatic b-cells. Plenum Press, New York, pp 189–193
Velasco JM (1987) Calcium channels in insulin-secreting RINm5F cell line. J Physiol 398:15P
Velasco JM, Petersen JUH, Petersen OH (1988) Single-channel Ba2+ currents in insulin-secreting cells are activated by glyceraldehyde stimulation. FEBS Lett 231: 366–370
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Rorsman, P., Ashcroft, F.M. & Trube, G. Single Ca channel currents in mouse pancreatic B-cells. Pflugers Arch. 412, 597–603 (1988). https://doi.org/10.1007/BF00583760
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DOI: https://doi.org/10.1007/BF00583760