Abstract
The cell membrane of sheep Purkinje fibres hyperpolarizes transiently on returning to K containing media after several minutes in K free solution. To analyse this ‘K activated response’ voltage clamp experiments and measurements of the internal Na activity (a iNa ) are performed in fibres bathed in solution containing 0.5–2 mM BaCl2. Compared to the response in Tyrode solution the transient hyperpolarization beyond the resting potential is increased in Ba containing media. The response is blocked by 10−4 M dihydroouabain. During the response, in Ba treated fibres, a iNa and a transient outward current decline with the same time constant at all clamp potentials tested. The transient outward current is most probably due to a temporary increase in electrogenic Na pumping. Both the amplitude and the time constant of the pump current show little voltage dependence. The electrogenic fraction of the active Na efflux is estimated to be about 39% and is independent of a iNa . Ba ions facilitate the analysis of the pump current in voltage clamped fibres because K depletion is reduced and changes of the I–V relationship by K depletion are minimized. It is concluded that activation of the electrogenic Na pump is mainly responsible for the K activated response of fibres in Ba containing media.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Aronson RS, Gelles JM, Hoffmann BF (1973) A new method for producing short cardiac Purkinje fibers suitable for voltage clamp. J Appl Physiol 34:527–530
Baumgarten CM, Isenberg G (1977) Depletion and accumulation of potassium in the extracellular clefts of cardiac Purkinje fibers during voltage clamp hyperpolarization and depolarization. Pflügers Arch 368:19–31
Christoffersen GRJ (1972) Steady state contribution of the Na, K-pump to the membrane potential in identified neurons of a terrestrial snail, Helix pomatia. Acta Physiol Scand 86:498–514
Cooke IM, Leblanc G, Tauc L (1974) Sodium pump stoichiometry inAplysia neurones from simultaneous current and tracer measurements. Nature (Lond) 251:254–256
Deck KA, Kern R, Trautwein W (1964) Voltage clamp technique in mammalian cardiac fibres. Pflügers Arch 280:50–62
De Mello WC (1976) Influence of the sodium pump on intercellular communication in heart fibres. Effect of intracellular injection of sodium ion on electrical coupling. J Physiol (Lond) 263:171–197
DiFrancesco D (1980) The pacemaker current ‘iK 2’ in Purkinje fibres is carried by sodium and potassium. J Physiol (Lond) 308:32–33 P
DiFrancesco D (1981) A new interpretation of the pace-maker current in calf Purkinje fibres. J Physiol (Lond) 314:359–376
Eisner DA, Lederer WJ (1980) Characterization of the electrogenic sodium pump in cardiac Purkinje fibres. J Physiol (Lond) 303:441–474
Eisner DA, Lederer WJ, Vaughan-Jones RD (1981) The dependence of sodium pumping and tension on intracellular sodium activity in voltage-clamped sheep Purkinje fibres. J Physiol (Lond) 317:163–187
Gadsby DC (1980) Activation of electrogenic Na+/K+ exchange by extracellular K+ in canine cardiac Purkinje fibers. Proc Natl Acad Sci USA 77:4035–4039
Gadsby DC, Cranefield PF (1979a) Direct measurement of changes in sodium pump current in canine cardiac Purkinje fibers. Proc Natl Acad Sci USA 76:1783–1787
Gadsby DC, Cranefield PF (1979b) Electrogenic sodium extrusion in cardiac Purkinje fibers. J Gen Physiol 73:819–837
Glitsch HG, Pusch H (1980) Correlation between changes in membrane potential and intracellular sodium activity during K activated response in sheep Purkinje fibres. Pflügers Arch 384:189–191
Glitsch HG, Kampmann W, Pusch H (1981 a) Activation of active Na transport in sheep Purkinje fibres by external K or Rb ions. Pflügers Arch 391:28–34
Glitsch HG, Pusch H, Verdonck F (1981 b) Ba2+ facilitate the analysis of the K activated response in sheep Purkinje fibres. Pflügers Arch 391 (Suppl):R8
Güggi M, Oehme M, Pretsch E, Simon W (1976) Neutraler, lonophor für Flüssigmembranelektroden mit hoher Selektivitär für Natriumgegenüber Kalium-Ionen. Helv Chim Acta 59:2417–2420
Isenberg G (1975) Is potassium conductance of cardiac Purkinje fibres controlled by [Ca2+]i? Nature (Lond) 253:273–274
Isenberg G, Trautwein W (1974) The effect of dihydro-ouabain and lithium-ions on the outward current in cardiac Purkinje fibers. Pflügers Arch 350:41–54
Kerkut GA, Thomas RC (1965) An electrogenic sodium pump in snail nerve cells. Comp Biochem Physiol 14:167–183
McAllister RE, Noble D (1966) The time and voltage dependence of the slow outward current in cardiac Purkinje fibres. J Physiol (Lond) 186:632–662
Mobley BA, Page E (1972) The surface area of sheep cardiac Purkinje fibres. J Physiol (Lond) 220:547–563
Noble D, Tsien RW (1968) The kinetics and rectifier properties of the slow potassium current in cardiac Purkinje fibres. J Physiol (Lond) 195:185–214
O'Doherty J, Garcia-Diaz JF, McD Armstrong W (1979) Sodium-selective liquid ion-exchanger microelectrodes for intracellular measurements. Science 203:1349–1351
Rang HP, Ritchie JM (1968) On the electrogenic sodium pump in mammalian non-myelinated nerve fibres and its activation by various external cations. J Physiol (Lond) 196:183–221
Reid JA, Hecht HH (1967) Barium-induced automaticity in right ventricular muscle in the dog. Circ Res 21:849–856
Thomas RC (1969) Membrane current and intracellular sodium changes in a snail neurone during extrusion of injected sodium. J Physiol (Lond) 201:495–514
Thomas RC (1970) New design for sodium sensitive glase microelectrode. J Physiol (Lond) 210:82–83 P
Vaughan-Jones RD, Lederer WJ, Eisner DA (1981) The electrogenic Na−K pump in the sheep cardiac Purkinje fibre. In: Lübbers DW, Acker H, Buck RP, Eisenman G, Kessler M, Simon W (eds) Progress in enzyme and ion-selective electrodes. Springer, Berlin Heidelberg New York, pp 156–163
Verdonck F, Glitsch HG, Pusch H (1981) The electrogenic sodium pump in heart: a comparison between sheep and rabbit Purkinje fibres. Arch Int Physiol Biochim 89:34–35 P
Author information
Authors and Affiliations
Additional information
This work was supported by the Deutsche Forschungsgemeinschaft (SFB 114 “Bionach”)
Rights and permissions
About this article
Cite this article
Glitsch, H.G., Pusch, H., Schumacher, T. et al. An identification of the K activated Na pump current in sheep Prkinje fibres. Pflugers Arch. 394, 256–263 (1982). https://doi.org/10.1007/BF00589101
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00589101