Na+/K+ ATPase and its functional coupling with Na+/Ca2+ exchanger in mouse embryonic stem cells during differentiation into cardiomyocytes

Keishi Otsu, Akinori Kuruma, Eri Yanagida, Satoshi Shoji, Takafumi Inoue, Yoshiyuki Hirayama, Hiroshi Uematsu, Yukichi Hara, Seiko Kawano

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15 Citations (Scopus)

Abstract

Cardiomyocytes derived from mouse embryonic stem (mES) cells have been demonstrated to exhibit a time-dependent expression of ion channels and signal transduction pathways in electrophysiological studies. However, ion transporters, such as Na+/K+ ATPase+ pump) or Na+/Ca2+ exchanger, which play crucial roles for cardiac function, have not been well studied in this system. In this study, we investigated the functional expression of Na+/K+ ATPase and Na+/Ca2+ exchanger in mES cells during in vitro differentiation into cardiomyocytes, as well as the functional coupling between the two transporters. By measuring [Na+]i and Na+ pump current (Ip), it was shown that an ouabain-high sensitive Na+/K+ ATPase was expressed functionally in undifferentiated mES cells and these activities increased during a time course of differentiation. Using RT-PCR, the expression of mRNA for α1-subunit and α3-subunit of the Na+/K+ ATPase could be detected in both undifferentiated mES cells and derived cardiomyocytes. In contrast α2-subunit mRNA could be detected only in derived cardiomyocytes but not in undifferentiated mES cells. mRNA for the Na+/Ca2+ exchanger 1 isoform (NCX1) could be detected in undifferentiated mES cells and its expression levels seemed to gradually increase throughout the differentiation accompanied by increasing its Ca2+ extrusion function. At the middle stages of differentiation (after 10-day induction), more than 75% derived cardiomyocytes exhibited [Ca2+]i oscillations by blocking of Na+/K+ ATPase, suggesting the functional coupling with Na+/Ca2+ exchanger. From these results and RT-PCR analysis, we conclude that α2-subunit Na+/K+ ATPase mainly contributes to establish the functional coupling with NCX1 at the middle stages of differentiation of cardiomyocytes.

Original languageEnglish
Pages (from-to)137-151
Number of pages15
JournalCell Calcium
Volume37
Issue number2
DOIs
Publication statusPublished - 2005 Feb
Externally publishedYes

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Keywords

  • Cardiomyocytes
  • Ion transporters
  • Mouse embryonic stem cells
  • Na/Ca exchanger
  • Na/K ATPase

ASJC Scopus subject areas

  • Cell Biology
  • Endocrinology

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