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Related Experiment Videos

Two functionally different Na/K pumps in cardiac ventricular myocytes

J Gao1, R T Mathias, I S Cohen

  • 1Department of Physiology and Biophysics, State University of New York at Stony Brook 11794-8661, USA.

The Journal of General Physiology
|November 1, 1995
PubMed
Summary

The study reveals two distinct types of sodium-potassium (Na/K) pumps in heart cells, each responding differently to ions like potassium and hydrogen. This suggests a complex regulation of Na/K pump activity tailored to specific tissues.

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Area of Science:

  • Cardiovascular Physiology
  • Cellular Electrophysiology
  • Membrane Transport

Background:

  • The sodium-potassium (Na/K) pump is crucial for maintaining cellular ion gradients.
  • Understanding its regulation is vital for cardiac function and disease.
  • Previous studies suggested a homogeneous Na/K pump population.

Purpose of the Study:

  • To investigate the functional heterogeneity of the Na/K pump in cardiac myocytes.
  • To characterize the distinct properties of different Na/K pump populations.
  • To elucidate the impact of the ionic environment on Na/K pump activity.

Main Methods:

  • Whole-cell patch-clamp electrophysiology on acutely isolated guinea pig and canine cardiac myocytes.
  • Voltage clamping at -60 mV to isolate Na/K pump current.

Related Experiment Videos

  • Dose-dependent inhibition using dihydro-ouabain (DHO) to differentiate pump types.
  • Systematic variation of intracellular and extracellular ion concentrations (Na+, K+, H+).

    • Main Results:

    • Two Na/K pump populations with distinct dihydro-ouabain (DHO) affinities (high: 0.75 µM, low: 72 µM) were identified.
    • Extracellular potassium (K+) half-maximally activated high-affinity pumps at 0.4 mM and low-affinity pumps at 3.7 mM.
    • Extracellular H+ blocked low-affinity pumps (pH 7.71) but not high-affinity pumps.
    • Both pump types showed similar half-maximal activation by intracellular Na+ (9.6 mM).
    • Canine Purkinje myocytes predominantly expressed high-affinity pumps, while ventricular myocytes showed a mix.

    Conclusions:

    • Mammalian ventricular myocytes possess at least two functionally distinct Na/K pump types.
    • Extracellular pH and K+ levels significantly modulate Na/K pump current via these different populations.
    • Intracellular Na+ concentration is a primary regulator of Na/K pump activity across both types.
    • Tissue-specific expression of Na/K pump variants allows for tailored physiological responses.