Abstract
1. In sodium-free solution electrical constants of short Purkinje fibres were similar to those in Tyrode solution. Alterations in the extracellular calcium concentration ([Ca]o = 0; 1·8; 7·2 mM) had no appreciable effect on these constants, unless the fibres were soaked in calcium-free solution for more than 40 min.
2. In sodium-free solution without calcium there was constant or increasing outward current in response to sudden depolarizations (voltage-clamp technique) over the whole voltage range -85 to +40 mV. In calcium-containing solution initial outward current was followed by a slow change in current towards zero which was sometimes large enough to produce a net inward current. This current had a threshold in the voltage range -60 to -40 mV. It was not affected by alterations in the extracellular chloride or magnesium concentrations. The dependence on [Ca]o suggests that the slow inward current is carried by calcium ions.
3. Negative slopes in the steady-state current—voltage relations were obtained in fibres soaked in calcium-containing solutions but were never observed in calcium-free solution.
4. The calcium equilibrium potential (ECa) was estimated to be about 150 mV, inside positive.
5. In Tyrode solution the slow inward current was smaller than in sodium-free solution and its threshold was shifted to about -20 to -10 mV. It was dependent on [Ca]o as in sodium-free solution. It was increased by adrenaline and not affected by tetrodotoxin.
6. It is concluded that calcium ions carry an appreciable membrane current in the inward direction when the membrane of the Purkinje fibre is depolarized. This calcium current may be involved in excitation—contraction coupling.
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Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- DECK K. A., KERN R., TRAUTWEIN W. VOLTAGE CLAMP TECHNIQUE IN MAMMALIAN CARDIAC FIBRES. Pflugers Arch Gesamte Physiol Menschen Tiere. 1964 Jun 9;280:50–62. doi: 10.1007/BF00412615. [DOI] [PubMed] [Google Scholar]
- DECK K. A., TRAUTWEIN W. IONIC CURRENTS IN CARDIAC EXCITATION. Pflugers Arch Gesamte Physiol Menschen Tiere. 1964 Jun 9;280:63–80. doi: 10.1007/BF00412616. [DOI] [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. doi: 10.1007/BF00362740. [DOI] [PubMed] [Google Scholar]
- Fozzard H. A. Membrane capacity of the cardiac Purkinje fibre. J Physiol. 1966 Jan;182(2):255–267. doi: 10.1113/jphysiol.1966.sp007823. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., HUXLEY A. F. Currents carried by sodium and potassium ions through the membrane of the giant axon of Loligo. J Physiol. 1952 Apr;116(4):449–472. doi: 10.1113/jphysiol.1952.sp004717. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., HUXLEY A. F. The components of membrane conductance in the giant axon of Loligo. J Physiol. 1952 Apr;116(4):473–496. doi: 10.1113/jphysiol.1952.sp004718. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Haas H. G., Kern R. Potassium fluxes in voltage clamped Purkinje fibres. Pflugers Arch Gesamte Physiol Menschen Tiere. 1966;291(1):69–84. doi: 10.1007/BF00362653. [DOI] [PubMed] [Google Scholar]
- Hagiwara S., Nakajima S. Differences in Na and Ca spikes as examined by application of tetrodotoxin, procaine, and manganese ions. J Gen Physiol. 1966 Mar;49(4):793–806. doi: 10.1085/jgp.49.4.793. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LANGER G. A., BRADY A. J. Calcium flux in the mammalian ventricular myocardium. J Gen Physiol. 1963 Mar;46:703–719. doi: 10.1085/jgp.46.4.703. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LUTTGAU H. C., NIEDERGERKE R. The antagonism between Ca and Na ions on the frog's heart. J Physiol. 1958 Oct 31;143(3):486–505. doi: 10.1113/jphysiol.1958.sp006073. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McAllister R. E., Noble D. The time and voltage dependence of the slow outward current in cardiac Purkinje fibres. J Physiol. 1966 Oct;186(3):632–662. doi: 10.1113/jphysiol.1966.sp008060. [DOI] [PMC free article] [PubMed] [Google Scholar]
- NIEDERGERKE R. Movements of Ca in beating ventricles of the frog heart. J Physiol. 1963 Jul;167:551–580. doi: 10.1113/jphysiol.1963.sp007167. [DOI] [PMC free article] [PubMed] [Google Scholar]
- NOBLE D. A modification of the Hodgkin--Huxley equations applicable to Purkinje fibre action and pace-maker potentials. J Physiol. 1962 Feb;160:317–352. doi: 10.1113/jphysiol.1962.sp006849. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Niedergerke R., Orkand R. K. The dual effect of calcium on the action potential of the frog's heart. J Physiol. 1966 May;184(2):291–311. doi: 10.1113/jphysiol.1966.sp007916. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Reuter H. Strom-Spannungsbeziehungen von Purkinje-Fasern bei verschiedenen extracellulären Calcium-Konzentrationen und unter Adrenalineinwirkung. Pflugers Arch Gesamte Physiol Menschen Tiere. 1966;287(4):357–367. [PubMed] [Google Scholar]
- Reuter H. Uber die Wirkung von Adrenalin auf den cellulären Ca-Umsatz des Meerschweinchenvorhofs. Naunyn Schmiedebergs Arch Exp Pathol Pharmakol. 1965 Aug 20;251(4):401–412. [PubMed] [Google Scholar]
- Vassalle M. Analysis of cardiac pacemaker potential using a "voltage clamp" technique. Am J Physiol. 1966 Jun;210(6):1335–1341. doi: 10.1152/ajplegacy.1966.210.6.1335. [DOI] [PubMed] [Google Scholar]
- WEIDMANN S. Effects of calcium ions and local anesthetics on electrical properties of Purkinje fibres. J Physiol. 1955 Sep 28;129(3):568–582. doi: 10.1113/jphysiol.1955.sp005379. [DOI] [PMC free article] [PubMed] [Google Scholar]
- WEIDMANN S. The electrical constants of Purkinje fibres. J Physiol. 1952 Nov;118(3):348–360. doi: 10.1113/jphysiol.1952.sp004799. [DOI] [PMC free article] [PubMed] [Google Scholar]
- WINEGRAD S., SHANES A. M. Calcium flux and contractility in guinea pig atria. J Gen Physiol. 1962 Jan;45:371–394. doi: 10.1085/jgp.45.3.371. [DOI] [PMC free article] [PubMed] [Google Scholar]