Ca 2+ ‐activated K + current is essential for maintaining excitability and gene transcription in early embryonic cardiomyocytes
Abstract Aim Activity of early embryonic cardiomyocytes relies on spontaneous Ca 2+ oscillations that are induced by interplay between sarcoplasmic reticulum ( SR ) – Ca 2+ release and ion currents of the plasma membrane. In a variety of cell types, Ca 2+ ‐activated K + current (I K(Ca) ) serves as...
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Published in | Acta Physiologica Vol. 216; no. 1; pp. 101 - 111 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
01.01.2016
|
Online Access | Get full text |
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Summary: | Abstract
Aim
Activity of early embryonic cardiomyocytes relies on spontaneous Ca
2+
oscillations that are induced by interplay between sarcoplasmic reticulum (
SR
) – Ca
2+
release and ion currents of the plasma membrane. In a variety of cell types, Ca
2+
‐activated K
+
current (I
K(Ca)
) serves as a link between Ca
2+
signals and membrane voltage. This study aimed to determine the role of
I
K
(Ca)
in developing cardiomyocytes.
Methods
Ion currents and membrane voltage of embryonic (E9‐11) mouse cardiomyocytes were measured by patch clamp; [Ca
2+
]
i
signals by confocal microscopy. Transcription of specific genes was measured with
RT
‐
qPCR
and Ca
2+
‐dependent transcriptional activity using
NFAT
‐luciferase assay. Myocyte structure was assessed with antibody labelling and confocal microscopy.
Results
E9‐11 cardiomyocytes express small conductance (
SK
) channel subunits
SK
2 and
SK
3 and have a functional apamin‐sensitive K
+
current, which is also sensitive to changes in cytosolic [Ca
2+
]
i
. In spontaneously active cardiomyocytes, inhibition of
I
K
(Ca)
changed action and resting potentials, reduced
SR
Ca
2+
load and suppressed the amplitude and the frequency of spontaneously evoked Ca
2+
oscillations. Apamin caused dose‐dependent suppression of
NFAT
‐luciferase reporter activity, induced downregulation of a pattern of genes vital for cardiomyocyte development and triggered changes in the myocyte morphology.
Conclusion
The results show that apamin‐sensitive
I
K
(Ca)
is required for maintaining excitability and activity of the developing cardiomyocytes as well as having a fundamental role in promoting Ca
2+
‐ dependent gene expression. |
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ISSN: | 1748-1708 1748-1716 |
DOI: | 10.1111/apha.12540 |