Electrophysiological Determination of Submembrane Na+ Concentration in Cardiac Myocytes

Bence Hegyi, Tamás Bányász, Thomas R. Shannon, Ye Chen-Izu, Leighton T Izu

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

In the heart, Na+ is a key modulator of the action potential, Ca2+ homeostasis, energetics, and contractility. Because Na+ currents and cotransport fluxes depend on the Na+ concentration in the submembrane region, it is necessary to accurately estimate the submembrane Na+ concentration ([Na+]sm). Current methods using Na+-sensitive fluorescent indicators or Na+ -sensitive electrodes cannot measure [Na+]sm. However, electrophysiology methods are ideal for measuring [Na+]sm. In this article, we develop patch-clamp protocols and experimental conditions to determine the upper bound of [Na+]sm at the peak of action potential and its lower bound at the resting state. During the cardiac cycle, the value of [Na+]sm is constrained within these bounds. We conducted experiments in rabbit ventricular myocytes at body temperature and found that 1) at a low pacing frequency of 0.5 Hz, the upper and lower bounds converge at 9 mM, constraining the [Na+]sm value to ∼9 mM; 2) at 2 Hz pacing frequency, [Na+]sm is bounded between 9 mM at resting state and 11.5 mM; and 3) the cells can maintain [Na+]sm to the above values, despite changes in the pipette Na+ concentration, showing autoregulation of Na+ in beating cardiomyocytes.

Original languageEnglish (US)
Pages (from-to)1304-1315
Number of pages12
JournalBiophysical Journal
Volume111
Issue number6
DOIs
StatePublished - Sep 20 2016

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Cardiac Myocytes
Action Potentials
Homeostasis
Electrophysiology
Body Temperature
Muscle Cells
Electrodes
Rabbits

ASJC Scopus subject areas

  • Biophysics

Cite this

Electrophysiological Determination of Submembrane Na+ Concentration in Cardiac Myocytes. / Hegyi, Bence; Bányász, Tamás; Shannon, Thomas R.; Chen-Izu, Ye; Izu, Leighton T.

In: Biophysical Journal, Vol. 111, No. 6, 20.09.2016, p. 1304-1315.

Research output: Contribution to journalArticle

Hegyi, Bence ; Bányász, Tamás ; Shannon, Thomas R. ; Chen-Izu, Ye ; Izu, Leighton T. / Electrophysiological Determination of Submembrane Na+ Concentration in Cardiac Myocytes. In: Biophysical Journal. 2016 ; Vol. 111, No. 6. pp. 1304-1315.
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