Abstract:

1. Rapid inward Na current (INa) was studied in isolated cells from rat ventricular myocardium by a double-suction-pipette voltage clamp technique. All experiments were carried out at 20-22 degrees C. 2. INa elicited by single depolarizing voltage steps from a holding potential, VH, of -80 mV had a threshold between -70 and -60 mV and was maximal at -30 to -20 mV. Peak currents in Krebs-Ringer solution containing 145 mM Na were of the order 0.9-1.8 mA cm-2, assuming an average cell surface area of 8000 square micrometers. 3. The reversal potential for INa was predicted by the Nernst equation for external Na in the range 1.45-145 mM with 16 mM-Na solution perfusing the interior of the cell. 4. Instantaneous I-V plots were linear for potentials of -100 to + 10 mV. Maximum Na conductance (-gNa) was calculated to be 25 mS cm-2 in 145 mM-Na solutions and gNa was constant for potentials positive to -10 mV. 5. INa activated with a time constant of 0.7 msec at -55 mV, decreasing to 100 microsec on depolarizations positive to + 10 mV. 6. Two time constants (tau h1, tau h2) were required to describe INa inactivation during a maintained depolarization, with tau h2 three to four times as long as tau h1. tau h1 was about 2 msec at -50 mV, decreasing to 0.9 msec at -10 mV. 7. The time course for recovery of INa from inactivation also exhibited two time constants (tau r1, tau r2), with the longer tau r2 having a maximum value of the order 100 msec in the potential range -60 to -80 mV. 8. INa in isolated rat cardiac cells has a low sensitivity to tetrodotoxin, requiring a concentration of 30 micrometers for complete blockade.

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Sodium current in single rat heart muscle cells.

A Brown

K Lee

T Powell

Abstract

1. Rapid inward Na current (INa) was studied in isolated cells from rat ventricular myocardium by a double-suction-pipette voltage clamp technique. All experiments were carried out at 20-22 degrees C. 2. INa elicited by single depolarizing voltage steps from a holding potential, VH, of -80 mV had a threshold between -70 and -60 mV and was maximal at -30 to -20 mV. Peak currents in Krebs-Ringer solution containing 145 mM Na were of the order 0.9-1.8 mA cm-2, assuming an average cell surface area of 8000 square micrometers. 3. The reversal potential for INa was predicted by the Nernst equation for external Na in the range 1.45-145 mM with 16 mM-Na solution perfusing the interior of the cell. 4. Instantaneous I-V plots were linear for potentials of -100 to + 10 mV. Maximum Na conductance (-gNa) was calculated to be 25 mS cm-2 in 145 mM-Na solutions and gNa was constant for potentials positive to -10 mV. 5. INa activated with a time constant of 0.7 msec at -55 mV, decreasing to 100 microsec on depolarizations positive to + 10 mV. 6. Two time constants (tau h1, tau h2) were required to describe INa inactivation during a maintained depolarization, with tau h2 three to four times as long as tau h1. tau h1 was about 2 msec at -50 mV, decreasing to 0.9 msec at -10 mV. 7. The time course for recovery of INa from inactivation also exhibited two time constants (tau r1, tau r2), with the longer tau r2 having a maximum value of the order 100 msec in the potential range -60 to -80 mV. 8. INa in isolated rat cardiac cells has a low sensitivity to tetrodotoxin, requiring a concentration of 30 micrometers for complete blockade.

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Attwell D, Cohen I, Eisner D, Ohba M, Ojeda C. The steady state TTX-sensitive ("window") sodium current in cardiac Purkinje fibres. Pflugers Arch. 1979 Mar 16;379(2):137–142. [PubMed] [Google Scholar]
Baer M, Best PM, Reuter H. Voltage-dependent action of tetrodotoxin in mammalian cardiac muscle. Nature. 1976 Sep 23;263(5575):344–345. [PubMed] [Google Scholar]
Beeler GW, Jr, Reuter H. Voltage clamp experiments on ventricular myocarial fibres. J Physiol. 1970 Mar;207(1):165–190.[PMC free article] [PubMed] [Google Scholar]
Bezanilla F, Armstrong CM. Inactivation of the sodium channel. I. Sodium current experiments. J Gen Physiol. 1977 Nov;70(5):549–566.[PMC free article] [PubMed] [Google Scholar]
Brown AM, Lee KS, Powell T. Voltage clamp and internal perfusion of single rat heart muscle cells. J Physiol. 1981 Sep;318:455–477.[PMC free article] [PubMed] [Google Scholar]
Chiu SY. Inactivation of sodium channels: second order kinetics in myelinated nerve. J Physiol. 1977 Dec;273(3):573–596.[PMC free article] [PubMed] [Google Scholar]
Cohen CJ, Colatsky TJ, Tsien RW. Tetrodotoxin block of cardiac sodium channels during repetitive or steady depolarizations in the rabbit [proceedings]. J Physiol. 1979 Nov;296:70P–71P. [PubMed] [Google Scholar]
Colatsky JJ, Tsien RW. Sodium channels in rabbit cardiac Purkinje fibres. Nature. 1979 Mar 15;278(5701):265–268. [PubMed] [Google Scholar]
Colatsky TJ. Voltage clamp measurements of sodium channel properties in rabbit cardiac Purkinje fibres. J Physiol. 1980 Aug;305:215–234.[PMC free article] [PubMed] [Google Scholar]
Dudel J, Peper K, Rüdel R, Trautwein W. Excitatory membrane current in heart muscle (Purkinje fibers). Pflugers Arch Gesamte Physiol Menschen Tiere. 1966;292(3):255–273. [PubMed] [Google Scholar]
Dudel J, Peper K, Rüdel R, Trautwein W. The effect of tetrodotoxin on the membrane current in cardiac muscle (Purkinje fibers). Pflugers Arch Gesamte Physiol Menschen Tiere. 1967;295(3):213–226. [PubMed] [Google Scholar]
Dudel J, Rüdel R. Voltage and time dependence of excitatory sodium current in cooled sheep Purkinje fibres. Pflugers Arch. 1970;315(2):136–158. [PubMed] [Google Scholar]
Ebihara L, Shigeto N, Lieberman M, Johnson EA. The initial inward current in spherical clusters of chick embryonic heart cells. J Gen Physiol. 1980 Apr;75(4):437–456.[PMC free article] [PubMed] [Google Scholar]
Gadsby DC, Cranefield PF. Two levels of resting potential in cardiac Purkinje fibers. J Gen Physiol. 1977 Dec;70(6):725–746.[PMC free article] [PubMed] [Google Scholar]
Gettes LS, Reuter H. Slow recovery from inactivation of inward currents in mammalian myocardial fibres. J Physiol. 1974 Aug;240(3):703–724.[PMC free article] [PubMed] [Google Scholar]
Goldman L. Kinetics of channel gating in excitable membranes. Q Rev Biophys. 1976 Nov;9(4):491–526. [PubMed] [Google Scholar]
Haas HG, Kern R, Einwächter HM, Tarr M. Kinetics of Na inactivation in frog atria. Pflugers Arch. 1971;323(2):141–157. [PubMed] [Google Scholar]
HODGKIN AL, HUXLEY AF. Currents carried by sodium and potassium ions through the membrane of the giant axon of Loligo. J Physiol. 1952 Apr;116(4):449–472.[PMC free article] [PubMed] [Google Scholar]
HODGKIN AL, HUXLEY AF. The components of membrane conductance in the giant axon of Loligo. J Physiol. 1952 Apr;116(4):473–496.[PMC free article] [PubMed] [Google Scholar]
HODGKIN AL, HUXLEY AF. The dual effect of membrane potential on sodium conductance in the giant axon of Loligo. J Physiol. 1952 Apr;116(4):497–506.[PMC free article] [PubMed] [Google Scholar]
Kenyon JL, Gibbons WR. Effects of low-chloride solutions on action potentials of sheep cardiac Purkinje fibers. J Gen Physiol. 1977 Nov;70(5):635–660.[PMC free article] [PubMed] [Google Scholar]
Lee KS, Weeks TA, Kao RL, Akaike N, Brown AM. Sodium current in single heart muscle cells. Nature. 1979 Mar 15;278(5701):269–271. [PubMed] [Google Scholar]
Lee KS, Akaike N, Brown AM. Trypsin inhibits the action of tetrodotoxin on neurones. Nature. 1977 Feb 24;265(5596):751–753. [PubMed] [Google Scholar]
Lee KS, Akaike N, Brown AM. Properties of internally perfused, voltage-clamped, isolated nerve cell bodies. J Gen Physiol. 1978 May;71(5):489–507.[PMC free article] [PubMed] [Google Scholar]
McAllister RE, Noble D. The time and voltage dependence of the slow outward current in cardiac Purkinje fibres. J Physiol. 1966 Oct;186(3):632–662.[PMC free article] [PubMed] [Google Scholar]
Meves H. Inactivation of the sodium permeability in squid giant nerve fibres. Prog Biophys Mol Biol. 1978;33(2):207–230. [PubMed] [Google Scholar]
Mobley BA, Page E. The surface area of sheep cardiac Purkinje fibres. J Physiol. 1972 Feb;220(3):547–563.[PMC free article] [PubMed] [Google Scholar]
Narahashi T. Chemicals as tools in the study of excitable membranes. Physiol Rev. 1974 Oct;54(4):813–889. [PubMed] [Google Scholar]
Powell T, Terrar DA, Twist VW. Electrical properties of individual cells isolated from adult rat ventricular myocardium. J Physiol. 1980 May;302:131–153.[PMC free article] [PubMed] [Google Scholar]
Forrester DW, Spence VA, Walker WF. The measurement of colonic mucosal-submucosal blood flow in man. J Physiol. 1980 Feb;299:1–11.[PMC free article] [PubMed] [Google Scholar]
Weidmann S. Electrical constants of trabecular muscle from mammalian heart. J Physiol. 1970 Nov;210(4):1041–1054.[PMC free article] [PubMed] [Google Scholar]

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Abstract

1. Rapid inward Na current (INa) was studied in isolated cells from rat ventricular myocardium by a double-suction-pipette voltage clamp technique. All experiments were carried out at 20-22 degrees C. 2. INa elicited by single depolarizing voltage steps from a holding potential, VH, of -80 mV had a threshold between -70 and -60 mV and was maximal at -30 to -20 mV. Peak currents in Krebs-Ringer solution containing 145 mM Na were of the order 0.9-1.8 mA cm-2, assuming an average cell surface area of 8000 square micrometers. 3. The reversal potential for INa was predicted by the Nernst equation for external Na in the range 1.45-145 mM with 16 mM-Na solution perfusing the interior of the cell. 4. Instantaneous I-V plots were linear for potentials of -100 to + 10 mV. Maximum Na conductance (-gNa) was calculated to be 25 mS cm-2 in 145 mM-Na solutions and gNa was constant for potentials positive to -10 mV. 5. INa activated with a time constant of 0.7 msec at -55 mV, decreasing to 100 microsec on depolarizations positive to + 10 mV. 6. Two time constants (tau h1, tau h2) were required to describe INa inactivation during a maintained depolarization, with tau h2 three to four times as long as tau h1. tau h1 was about 2 msec at -50 mV, decreasing to 0.9 msec at -10 mV. 7. The time course for recovery of INa from inactivation also exhibited two time constants (tau r1, tau r2), with the longer tau r2 having a maximum value of the order 100 msec in the potential range -60 to -80 mV. 8. INa in isolated rat cardiac cells has a low sensitivity to tetrodotoxin, requiring a concentration of 30 micrometers for complete blockade.

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