Abstract
Elementary Ca2+ and Ba2+ currents were recorded from cell-attached membrane patches of ventricular myocytes from adult guinea pig hearts using the improved patch-clamp technique (Hamill et al. 1981). High concentrations of Ba2+ or Ca2+ (50 or 90 mM) were used in the pipettes to increase the signal-to-noise ratio. All data were derived from elementary current analyses in patches containing only one channel.
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1)
In response to voltage steps, channel openings occurred singly or in bursts of closely spaced unitary current pulses separated by wider shut intervals. During depolarizations of small amplitude from the resting potential, channel openings occurred almost randomly, whereas during larger depolarizations the events were grouped preferentially at the beginning.
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2)
Channel openings became more probable with increased depolarization; simultaneously, unitary current amplitudes declined in an ohmic manner. Elementary current amplitudes were slightly larger, when 50 mM Ba2+ replaced 50 mM Ca2+ in the pipettes (slope conductances 9 and 10 pS, respectively), but more than doubled, when Ba2+ was increased to 90 mM (slope conductance 18 pS). Clear outward currents through Ca2+ channels were not observed under these conditions.
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3)
Peak amplitudes of reconstructed mean currents doubled when 50 mM Ba2+ replaced 50 mM Ca2+ and were larger still when 90 mM Ba2+ was used in the pipettes. The current-volrage relations of the reconstructed mean currents showed a positive shift along the voltage axis as Ba2+ was increased or substituted equimolarly by Ca2+. Correspondingly, the open state probability-voltage relations (activation curves) showed a parallel shift as Ba2+ was increased, which was less pronounced when Ba2+ was replaced equimolarly by Ca2+.
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4)
Determination of Ca2+ channel inactivation using 90 mM Ba2+ in the pipettes indicated an overlap with channel activation in a limited voltage range, resulting in a steadystate “window” current. Inactivation can occur without divalent cation influx.
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5)
Formation of an inside-out patch resulted in a fast rundown of elementary Ca2+ channel currents.
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6)
Channel openings were often grouped in bursts. The lifetimes of the open state, the bursts, and the closed states were estimated for Ba2+ and Ca2+ as permeating ions. At least two exponentials were needed to fit the histogram of the lifetimes of all closed states. The lifetimes of the individual openings and bursts were mono-exponentially distributed. The kinetics of the Ca+ channel depended on the voltage and the permeating ion. During +30 mV depolarizations, no significant effect of the permeating ion on channel gating could be detected. The significant increase in burst length (t b) during +50 mV depolarizations, however, seemed to be only due to an increase in the lifetime of the open state (t o) for Ba2+, whereas for Ca2+,t o was only moderately prolonged but simultaneously, the number of openings per burst increased.
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A three-state sequential scheme is peoposed to model the activation pathway of Ca2+ channels. The latency-to-first-event histogram is also consistent with a process in which multiple closed states precede the open state.
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References
Adams DJ, Gage PW (1980) Divalent ion currents and the delayed potassium conductance in an Aplysia neurone. J Physiol (Lond) 304:297–313
Akaike N, Lee KS, Brown AM (1978) The calcium current of Helix neurone. J Gen Physiol 71:509–531
Almers W, Palade PT (1981) Slow calcium and potassium currents across frog muscle membrane: measurements with a vasiline-gap technique. J Physiol (Lond) 312:159–176
Armstrong CM, Bezanilla F (1975) Currents associated with the ionic gating structures in nerve membrane. Ann NY Acad Sci 264:265–277
Armstrong CM, Gilly WF (1979) Fast and slow steps in the activation of sodium channels. J Gen Physiol 74:691–711
Ashcroft FM, Stanfield PR (1981) Calcium dependence of the inactivation of calcium currents in skeletal muscle fibers of an insect. Science 213:224–226
Brehm P, Eckert R (1978) Calcium entry leads to inactivation of calcium channel in Paramecium. Science 202:1203–1206
Brown AM, Morimoto K, Tsuda Y, Wilson DL (1981) Calcium current-dependent and voltage-dependent inactivation of calcium channels in Helix aspersa. J Physiol (Lond) 320:193–218
Brown AM, Camerer H, Kunze DL, Lux HD (1982) Similarity of unitary Ca2+ currents in three different species. Nature (Lond) 299:156–158
Byerly L, Hagiwara S (1982) Calcium currents in internally perfused nerve cell bodies of Limnea stagnalis. J Physiol (Lond) 322:503–528
Cavalié A, Trautwein W (1983) Single calcium channels in heart —elementary and reconstructed mean currents. Naunyn-Schmiedeberg's Arch Pharmacol 322:R64
Ciani S, Krasne S, Miyazaki S, Hagiwara S (1978) A model for anomalous rectification: electrochemical-potential-dependent gating of membrane channels. J Membr Biol 44:103–134
Colquhoun D, Hawkes AG (1981) On the stochastic properties of single ion channels. Proc R Soc Lond B211:205–235
Dow JW, Harding NGL, Powell T (1981) Isolated cardiac myocytes. I. Preparation of adult myocytes and their homology with the intact tissue. Cardiovasc Res 15:483–514
Fenwick EM, Marty A, Neher E (1982) Sodium and calcium channels in bovine chromaffin cells. J Physiol (Lond) 331:599–635
Gilbert DL (1971) Fixed surface charges. In: Adelman WJ Jr (ed) Biophysics and physiology of excitable membranes. Van Nostrand Reinhold, New York
Hagiwara S, Miyazaki S, Krasne S, Ciani S (1977) Anomalous permeabilities of the egg cell membrane of a starfish in K+−TI+ mixtures. J Gen Physiol 70:269–281
Hagiwara S, Byerly L (1981) Calcium channel. Ann Rev Neurosci 4:69–125
Hagiwara S, Ohmori H (1982) Studies of calcium channels in rat clonal pituitary cells with patch electrode voltage clamp. J Physiol (Lond) 331:231–252
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
Hescheler J, Pelzer D, Trube G, Trautwein W (1982) Does the organic calcium channel blocker D600 act from inside or outside on the cardiac cell membrane? Pflügers Arch 393:287–291
Hino N, Ochi R (1980) Effect of acetylcholine on membrane currents in guinea-pig papillary muscle. J Physiol (Lond) 307:183–197
Horn R, Patlak J, Stevens CF (1981) Sodium channels need not open before they inactivate. Nature (Lond) 291:426–427
Irisawa H, Yanagihara K (1980) The slow inward current of the rabbit sino-atrial nodal cells. In: Zipes DP, Bailey JC, Elharrar V (eds) The slow inward current and cardiac arrhythmias. Martinus Nijhoff Publishers The Hague, pp 265–284
Isenberg G, Klöckner U (1981) Ca currents of isolated bovine ventricular myocytes. In: Ohnishi ST, Endo M (eds) The mechanism of gated calcium transport across biological membranes. Academic Press, New York, London, pp 25–33
Isenberg G, Klöckner U (1982a) Calcium tolerant ventricular myocytes prepared by preincubation in a “KB-medium”. Pflügers Arch 395:6–18
Isenberg G, Klöckner U (1982b) Calcium currents of isolated bovine ventricular myocytes are fast and of large amplitude. Pflügers Arch 395:30–41
Kohlhardt M, Krause H, Kübler M, Herdey A (1975) Kinetics of inactivation and recovery of the slow inward current in the mammalian ventricular myocardium. Pflügers Arch 355:1–17
Kostyuk PG, Krishtal OA, Shakhovalov YA (1977) Separation of sodium and calcium currents in the somatic membrane of mollusc neurones. J Physiol (Lond) 270:545–568
Kostyuk PG (1981) Calcium channels in the neuronal membrane. Biochim Biophys Acta 650:128–150
Kostyuk PG, Krishtal OA, Pidoplichko VI (1981) Calcium inward current and related charge movements in the membrane of snail neurones. J Physiol (Lond) 310:403–421
Lee KS, Lee EW, Tsien RW (1981) Slow inward current carried by Ca2+ or Ba2+ in single isolated heart cells. Biophys J 33:143a
Lee KS, Tsien RW (1982) Reversal of current through calcium channels in dialysed single heart cells. Nature (Lond) 297:498–501
Leech CA, Stanfield PR (1981) Inward rectification in frog skeletal muscle fibres and its dependence on membrane potential and external potassium. J Physiol (Lond) 319:295–309
Llinas R, Steinberg IZ, Walton K (1981) Presynaptic calcium currents in squid giant synapse. Biophys J 33:289–322
Lux HD, Nagy K (1981) Single channel Ca2+ currents in Helix pomatia neurones. Pflügers Arch 391:252–254
McDonald TF, Trautwein W (1978) Membrane currents in cat myocardium: separation of inward and outward components. J Physiol (Lond) 274:193–216
McDonald TF (1982) The slow inward calcium current in the heart. Ann Rev Physiol 44:425–434
Meves H (1976) The effect of zinc on the late displacement current in squid giant axons. J Physiol (Lond) 254:787–801
Noma A, Kotake H, Irisawa H (1980) Slow inward current and its role mediating the chronotropic effect of epinephrine in the rabbit sinoatrial node. Pflügers Arch 388:1–9
Ohmori H, Yoshii M (1977) Surface potential reflected in both gating and permeation mechanisms of sodium and calcium channels of the tunicate egg cell membrane. J Physiol (Lond) 267:429–463
Okamoto H, Takahashi K, Yoshii M (1976) Two components of the calcium current in the egg cell membrane of the tunicate. J Physiol (Lond) 255:527–561
Osterrieder W, Pelzer D, Yang Q-f, Trautwein W (1981) The electrophysiological basis of the bradycardic action of AQA 39 in the sinoatrial node. Naunyn-Schmiedeberg's Arch Pharmacol 317:233–237
Osterrieder W, Yang Q-F, Trautwein W (1982a) Effects of barium on the membrane currents in the rabbit S-A node. Pflügers Arch 394:78–84
Osterrieder W, Yang Q-F, Trautwein W (1982b) Conductance of the slow inward channel in the rabbit sinotrial node. Pflügers Arch 394:85–89
Osterrieder W, Brum G, Hescheler J, Trautwein W, Flockerzi V, Hofmann F (1982c) Injection of subunits of cyclic AMP-dependent protein kinase into cardiac myocytes modulates Ca2+ current. Nature (Lond) 298:576–578
Patlak J, Horn R (1982) Effect of N-Bromoacetamide on single sodium channel currents in excised membrane patches. J Gen Physiol 79:333–351
Pelzer D, Trautwein W, McDonald TF (1982) Calcium channel block and recovery from block in mammalian ventricular muscle treated with organic channel inhibitors. Pflügers Arch 394:97–105
Pelzer D, Ochi R (1983) Single calcium channels in heart — kinetic properties of elementary currents. Naunyn-Schmiedeberg's Arch Pharmacol 322:R64
Reuter H (1973) Divalent cations as charge carriers in excitable membranes. Prog Biophys Mol Biol 26:1–43
Reuter H, Scholz H (1977) A study of the ion selectivity and the kinetic properties of the calcium dependent slow inward current in mammalian cardiac muscle. J Physiol (Lond) 264:17–47
Reuter H, Stevens CF, Tsien RW, Yellen G (1982) Properties of single calcium channels in cardiac cell culture. Nature (Lond) 297:501–504
Reuter H (1983) Calcium channel modulation by neurotransmitters, enzymes and drugs. Nature (Lond) 301:569–574
Saimi Y, Kung C (1982) Are ions involved in the gating of calcium channels? Science 218:153–156
Sakmann B, Trube G (1983) Voltage-dependent inactivation of potassium single channel currents in the heart cel membrane showing inward rectification. J Physiol (Lond) submitted
Standen NB (1981) Ca2+ channel inactivation by intracellular Ca2+ injection into Helix neurones. nature (Lond) 293:158–159
Standen NB, Stanfield PR (1982) A binding-site model for calcium channel inactivation that depends on calcium entry. Proc R Soc Lond B217:101–110
Swenson RP Jr, Armstrong CM (1981) K+ channels close more slowly in the presence of external K+ and Rb+. Nature (Lond) 291:427–429
Taniguchi J, Kokubun S, Noma A, Irisawa H (1981) Spontaneously active cells isolated from the sino-atrial and atrio-ventricular nodes of rabbit heart. Jpn J Physiol 31:547–558
Trautwein W, McDonald TF, Tripathi O (1975) Calcium conductance and tension in mammalian ventricular muscle. Pflügers Arch 354:55–74
Trautwein W, Taniguchi J, Noma A (1982) The effect of intracellular cyclic nucleotides and calcium on the action potential and acetylcholine response of isolated cardiac cells. Pflügers Arch 392:307–314
Tillotson D, Horn R (1978) Inactivation without facilitation of calcium conductance in caesium-loaded neurones of Aplysia. Nature (Lond) 273:312–314
Tillotson D (1979) Inactivation of Ca conductance dependent on entry of Ca ions in molluscan neurones. Proc Natl Acad Sci USA 76:1497–1500
Tsuda Y, Wilson DL, Brown AM (1982) Calcium tail currents in snail neurones. Biophys J 37:181a
Zipes DP, Bailey JC, Elharrar V (1980) The slow inward current and cardiac arrhythmias. Martinus Nijhoff Publishers, The Hague
Wilson DL, Tsuda Y, Brown AM (1982) Activation of calcium channels in snail neurones. Biophys J 37:181a
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Supported by the DFG, SFB 38, project G1
Supported by the DAAD, German Academic Exchange Service
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Cavalié, A., Ochi, R., Pelzer, D. et al. Elementary currents through Ca2+ channels in Guinea pig myocytes. Pflugers Arch. 398, 284–297 (1983). https://doi.org/10.1007/BF00657238
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DOI: https://doi.org/10.1007/BF00657238