Uniform action potential repolarization within the sarcolemma of in situ ventricular cardiomyocytes

Guixue Bu, Heather Adams, Edward J. Berbari, Michael Rubart

Research output: Contribution to journalArticle

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Abstract

Previous studies have speculated, based on indirect evidence, that the action potential at the transverse (t)-tubules is longer than at the surface membrane in mammalian ventricular cardiomyocytes. To date, no technique has enabled recording of electrical activity selectively at the t-tubules to directly examine this hypothesis. We used confocal line-scan imaging in conjunction with the fast response voltage-sensitive dyes ANNINE-6 and ANNINE-6plus to resolve action potential-related changes in fractional dye fluorescence (ΔF/F) at the t-tubule and surface membranes of in situ mouse ventricular cardiomyocytes. Peak ΔF/F during action potential phase 0 depolarization averaged -21% for both dyes. The shape and time course of optical action potentials measured with the water-soluble ANNINE-6plus were indistinguishable from those of action potentials recorded with intracellular microelectrodes in the absence of the dye. In contrast, optical action potentials measured with the water-insoluble ANNINE-6 were significantly prolonged compared to the electrical recordings obtained from dye-free hearts, suggesting electrophysiological effects of ANNINE-6 and/or its solvents. With either dye, the kinetics of action potential-dependent changes in ΔF/F during repolarization were found to be similar at the t-tubular and surface membranes. This study provides what to our knowledge are the first direct measurements of t-tubule electrical activity in ventricular cardiomyocytes, which support the concept that action potential duration is uniform throughout the sarcolemma of individual cells.

Original languageEnglish (US)
Pages (from-to)2532-2546
Number of pages15
JournalBiophysical Journal
Volume96
Issue number6
DOIs
StatePublished - Jan 1 2009

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Sarcolemma
Cardiac Myocytes
Action Potentials
Coloring Agents
Fluorescence
Membranes
Water
Microelectrodes

ASJC Scopus subject areas

  • Biophysics

Cite this

Uniform action potential repolarization within the sarcolemma of in situ ventricular cardiomyocytes. / Bu, Guixue; Adams, Heather; Berbari, Edward J.; Rubart, Michael.

In: Biophysical Journal, Vol. 96, No. 6, 01.01.2009, p. 2532-2546.

Research output: Contribution to journalArticle

Bu, Guixue ; Adams, Heather ; Berbari, Edward J. ; Rubart, Michael. / Uniform action potential repolarization within the sarcolemma of in situ ventricular cardiomyocytes. In: Biophysical Journal. 2009 ; Vol. 96, No. 6. pp. 2532-2546.
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