Pflügers Archiv

, Volume 404, Issue 2, pp 190–196 | Cite as

Sodium current in single myocardial mouse cells

  • Klaus Benndorf
  • Wolfgang Boldt
  • Bernd Nilius
Excitable Tissues and Central Nervous Physiology


Morphologically intact single myocardial cells of the adult mouse show a length of 132±20 μm, a width of 21±5 μ, and a height of 10±4 μm (all mean ± SD) and are brick-like in shape. A one suction pipette method is used for voltage clamp of those single cells. The determined time constant of capacitive current τ=35±14 μs is very short. Series resistancers, membrane resistancerm, and membrane capacitycm are calculated to be 192±48 kΩ, 6.1±1.1 MΩ, and 186±92 pF (all mean ± SD), respectively. Assuming the specific unit membrane capacitance of 1 μF/cm2, a total membrane area of 1.86×10−4 cm2 is determined yielding a specific membrane resistanceRm of 1,134 Ωcm2. Settling time of voltage clamp is 30 μs. TTX-block of sodium current is described by 1:1 binding with aKD value of 1.4×10−6M. Using a reduced extracellular sodium concentration the maximum Na current is between 25 and 40 nA at voltages between −40 and −30 mV. Currents of between +20 and +30 mV reverse in an outward direction. Inward currents are approximated by a m3h model. The time constant of activation decreases from 0.7 ms at −60 mV to 0.12 ms at +20 mV. The time constant of inactivation falls from 9.1 ms at −60 mV to 0.6 ms at +20 mV.

Steady state inactivationh is characterized by the half maximum valueVH=−76.1±4.3 mV and the slope parameters=−6.3±1.1 mV (mean ± SD). A prepulse duration of 500 ms is essential for real steady state inactivation. Steady state activationm and inactivationh overlap each other defining a maximum window current at −65 mV.

Key words

Single myocardial mouse cells Sodium current Current voltage relation m h 


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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Klaus Benndorf
    • 1
  • Wolfgang Boldt
    • 1
  • Bernd Nilius
    • 1
  1. 1.Julius Bernstein Institute for PhysiologyMartin Luther University Halle WittenbergHalle (Saale)German Democratic Republic

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