Abstract
Inactivation of voltage-dependent calcium currents was studied in single, dissociated insulin-secreting HIT cells voltage-clamped by the whole-cell patch-clamp method at room temperature. Na and K currents were suppressed by tetrodotoxin, tetraethylammonium, ATP, 4-aminopyridine and Cs. Ca currents activated in less than 10 ms by depolarizations beyond −50 mV from a holding potential of −100 mV and were identified, as in previous studies, by their sensitivity to divalent cation blockade and permeability to Ba as a charge carrier. Sustained depolarization revealed two kinetically distinct phases of inactivation: a rapid phase inactivated approximately 50% of the current in less than 100 ms while the remaining current was inactivated over the next 10–20 s. Rapid inactivation appeared to be due to Ca2+ influx since it was slowed markedly when Ba2+ was used as the current carrier, while the degree of inactivation mercased and decreased with increasing depolarization in direct parallel with the U-shaped current-voltage relationship for inward Ca current. Slow inactivation appeared to be voltage-dependent since current could be inactivated (by ≈20%) by 10 s long depolarizations to potentials below the threshold for activating Ca current, slow time constants of inactivation were voltage-dependent and slow inactivation persisted when Ca was replaced with Ba. Ca currents with low activation thresholds (in the −50 to −30 mV range) appeared to be preferentially inactivated by the rapid Ca-dependent mechanism. Recovery of slowly inactivated Ca current was very slow and currents inactivated by larger depolarizations required longer recovery time than those elicited by smaller depolarizations. Rapid and slow inactivation mechanisms may be important in understanding the fast spiking and slow plateau depolarizations seen in pancreatic B-cells exposed to stimulatory levels of glucose.
Similar content being viewed by others
References
Atwater I, Dawson CM, Eddlestone GT, Rojas E (1981) Voltage noise measurements across the pancreatic β-cell membrane: calcium channel characteristics. J Physiol 314:195–212
Bean B (1985) Two kinds of Ca channels in canine atrial cells. J Gen Physiol 86:1–30
Brehm P, Eckert R (1978) Calcium entry leads to inactivation of calcium channel inParamecium. Science 202:1203–1206
Brown AM, Morimoto K, Tsuda Y, Wilson DL (1981) Calcium current-dependent and voltage-dependent inactivation of calcium channels inHelix aspersa. J Physiol 320:193–218
Byerly L, Hagiwara S (1982) Calcium currents in internally perfused neurones of the snailLimnaea stagnalis. J Physiol 322:503–528
Byerly L, Meech R, Moody Jr W (1984) Rapidly activating hydrogen ion currents in perfused neurones of the snailLimnaea stagnalis. J Physiol 351:199–216
Carbone E, Lux HD (1984) A low voltage-activated calcium conductance in embryonic chick sensory neurons. Biophys J 46:413–418
Carbone E, Lux HD (1987) Kinetics and selectivity of a low-voltageactivated calcium current in chick and rat sensory neurones. J Physiol 386:547–570
Chad JE, Eckert RO (1986) An enzymatic mechanism for calcium current inactivation in dialyzedHelix neurones. J Physiol 378:31–51
Chay TR, Keizer J (1985) Minimal model for membrane oscillations in the pancreatic islet B-cell. Biophys J 42:181–190
Cook DL (1984) Electrical pacemaker mechanisms of pancreatic islet cells. Fed Proc 43:2386–2392
Cook DL, Hales CN (1984) Intracellular ATP directly blocks K channels in pancreatic islet cells. Nature 311:271–273
Cook DL, Porte Jr D, Crill WE (1981) Voltage dependence of rhythmic plateau potentials of pancreatic islet cells. Am J Physiol 240:E290–296
Cook DL, Ikeuchi M, Fujimoto W (1984) Lowering of pHi inhibits Ca-activated K channels in pancreatic B-cells. Nature 311: 269–271
Dean PM, Matthews EK (1970a) Glucose-induced electrical activity in pancreatic islet cells. J Physiol 210:255–264
Dean PM, Matthews EK (1970b) Electrical activity in pancreatic islet cells: effect of ions. J Physiol 210:265–275
Dupont J-L, Bossu J-L, Feltz A (1986) Effect of internal calcium concentration on calcium currents in rat sensory neurones. Pflügers Arch 406:433–435
Eckert RO, Chad JE (1984) Inactivation of Ca channels. Prog Biophys Mol Biol 44:215–267
Eckert RO, Lux HD (1976) A voltage-sensitive persistant calcium conductance in neuronal somata ofHelix. J Physiol 254:129–151
Eckert RO, Tillotson D (1981) Calcium-mediated inactivation of the calcium conductance in caesium-loaded giant neurones ofAplysia calfornica. J Physiol 314:265–280
Fedulova SA, Kostyuk PG, Veselovsky NS (1985) Two types of Ca channels in the somatic membrane of new-born rat dorsal root ganglion neurones. J Physiol 359:431–446
Findlay I, Dunne MJ (1985) Voltage-activated Ca2+ currents in insulin-secreting cells. FEBS Lett 189:281–285
Findlay I, Dunne MJ (1986) Voltage-activated Ca2+ and K+ currents in an insulin-secreting cell line (RINm5F). In: Atwater I, Rojas E (eds) Biophysics of the B-cell. Raven Press, New York, pp 177–187
Findlay I, Dunne MJ, Ullrich S, Wollheim CB, Petersen O (1985) Quinine inhibits Ca2+-independent K+ channels whereas tetraethylammonium inhibits Ca2+-activated K+ channels in insulin-secreting cells. FEBS Lett 185:4–8
Fox AP, Nowycky MC, Tsien RW (1987a) Kinetic and pharmacological properties distinguishing three types of calcium currents in chick sensory neurones. J Physiol 394:149–172
Fox AP, Nowycky MC, Tsien RW (1987b) Single-channel recordings of three types of calcium channels in chick sensory neurones. J Physiol 394:173–200
Gola M (1978) A model for the production of slow potential waves and associated spiking in molluscan neurons. In: Chalazonitis N, Boisson M (eds) Abnormal neuronal discharges. Raven Press, New York, pp 243–261
Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ (1981) Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflügers Arch 391:85–100
Hennessey TM, Kung C (1985) Slow inactivation of the calcium current ofParamecium is dependent on voltage and not internal calcium. J Physiol 365:165–179
Henquin JC, Meissner HP (1984) Significance of ionic fluxes and changes in membrane potential for stimulus-secretion coupling in pancreatic B-cells. Experientia 40:1043–1052
Henquin JC, Schmeer W, Nenquin M, Meissner HP (1985) Effects of a calcium channel agonist on the electrical, ionic, and secretory events in mouse pancreatic B-cells. Biochem Biophys Res Commun 131:980–986
Hess P, Tsien RW (1984) Mechanism of ion permeation through calcium channels. Nature 309:453–456
Hille B (1984) Ionic channels of excitable membranes. Sinauer Associates Inc., Sunderland, MA
Hiriart M, Matteson DR (1987) Patch clamp study of ionic channels in rat pancreatic B-cells identified with the reverse hemolytic plaque assay. Biophys J 51:250a
Hiriart M, Matteson DR (1988) Na Channels and tow types of Ca channels in rat pancreatic B cells identified with the reverse hemolytic plaque assay. J Gen Physiol 91:617–639
Jmari K, Mironneau C, Mironneau J (1986) Inactivation of calcium channel current in rat uterine smooth muscle: evidence for calcium- and voltage-mediated mechanisms. J Physiol 380: 111–126
Kass RS, Sanguinetti MC (1984) Inactivation of calcium channel current in the calf cardiac Purkinje fiber: Evidence for voltage- and calcium-mediated mechanisms. J Gen Physiol 84:705–726
Kostyuk PA, Veselovsky NS, Fedulova SA (1981) Ionic currents in the somatic membrane of the rat dorsal root ganglion neurons. II. Calcium currents. Neuroscience 6:2431–2437
Lee KS, Marban E, Tsien RW (1985) Inactivation of calcium channels in mammalian heart cells: joint dependence on membrane potential and intracellular calcium. J Physiol 364:395–411
Marty A, Neher E (1985) Potassium channels in cultured bovine adrenal chromaffin cells. J Physiol 367:117–141
Matteson DR, Matschinsky FM (1986) Identification of several types of voltage and/or Ca activated channels in a pancreatic beta cell line. Biophys J 49:432a
Meda P, Kohen C, Rabinovich A, Orci L (1982) Direct communication of homologous and heterologous endocrine islet cells in culture. J Cell Biol 92:221–226
Meissner HP, Schmeer W (1981) The significance of calcium ions for the glucose-induced electrical activity of pancreatic B cells. In: Ohnishi S, Endo M (eds) The mechanism of gated calcium transport across biological membranes. Academic Press, New York, pp 157–165
Meissner HP, Schmelz H (1974) Membrane potential of B-cells in pancreatic islets. Pflügers Arch 351:195–206
Miller RJ (1987) Multiple calcium channels and neuronal function. Science 235:46–52
Nakazawa K, Saito H, Matsuki N (1988) Fast and slowly inactivating components of Ca-channel current and their sensitivities to nicardipine in isolated smooth muscle cells from rat vas deferens. Pflügers Arch 411:289–295
Nowycky M, Fox AP, Tsien RW (1985) Three types of neuronal calcium channels with different agonist sensitivity. Nature 316:440–443
Plant TD (1987) Calcium current inactivation in cultured mouse pancreatic islet cells is calcium-dependent. J Physiol 390:86P
Ribalet B, Beigelman PM (1980) Calcium action potentials and potassium permeability activation in pancreatic B-cells. AM J Physiol 239:C124-C133
Ribalet B, Beigelman PM (1981) Effects of divalent cations on B-cell electrical activity. Am J Physiol 241:C59-C67
Rorsman P, Trube G (1986) Calcium and delayed potassium currents in mouse pancreatic B-cells under voltage-clamp conditions. J Physiol 374:531–550
Santerre RF, Cook RA, Crisel RMD, Sharp JD, Schmidt RJ, Williams DC, Wilson CP (1981) Insulin synthesis in a clonal cell line of simian virus 40-transformed hamster pancreatic beta cells. Proc Natl Acad Sci USA 78:4339–4343
Satin LS, Cook DL (1985) Voltage-gated Ca current in pancreatic islet B-cells. Pflügers Arch 404:385–387
Satin LS, Cook DL (1987) Properties of the calcium current in pancreatic B-cells. Soc Neurosci 13:794
Satin LS, Cook DL (1988) Evidence for two calcium currents in insulin-secreting cells. Pflügers Arch 411:401–409
Tillotson D (1979) Inactivation of Ca conductance dependent on entry of Ca ions in molluscan neurons. Proc Natl Acad Sci USA 76:1499–1500
Wollheim CB, Pozzan T (1984) Correlation between cytosolic free Ca2+ and insulin release in an insulin-secreting cell line. J Biol Chem 259:2262–2267
Wollheim CB, Sharp WG (1981) Regulation of insulin release by calcium. Physiol Rev 61:914–973
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Satin, L.S., Cook, D.L. Calcium current inactivation in insulin-secreting cells is mediated by calcium influx and membrane depolarization. Pflugers Arch. 414, 1–10 (1989). https://doi.org/10.1007/BF00585619
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00585619