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Nuclear ion channels in cardiac myocytes
1Department of Physiology, University of Ottawa Heart Institute, Ontario, Canada.
Pflugers Archiv : European Journal of Physiology
|August 1, 1992
Summary
Nuclear ion channels (NIC) exist in cardiac myocytes, challenging previous transport models. Phosphorylation regulates these channels, suggesting a role in nucleocytoplasmic transport.
Area of Science:
- Cell Biology
- Molecular Biology
- Cardiology
Background:
- Nucleocytoplasmic transport was thought to lack diffusional barriers.
- Recent studies revealed ion channels in the nuclear envelope of other cell types.
Purpose of the Study:
- To demonstrate the existence of nuclear ion channels (NIC) in murine ventricular cardiac myocytes.
- To investigate the properties and regulation of these NIC.
Main Methods:
- Patch-clamp techniques were used on murine ventricular cardiac myocytes.
- Nucleus-attached and excised, inside-out patch configurations were employed.
- Ion substitution, Mg2+, ATP2-, Ca2+, and protein kinase manipulations were performed.
Main Results:
- Nuclear ion channels (NIC) were identified in cardiac myocytes with conductances of 106-532 pS.
- NIC activity was sensitive to cytoplasmic K+ and Na+ concentrations.
- K+ and Na+ showed similar permeability through NIC.
- NIC function was regulated by phosphorylation, dependent on cAMP-dependent protein kinase, Mg2+, and ATP2-.
- Ca2+ played a minor direct role.
Conclusions:
- Nuclear ion channels (NIC) are present in cardiac myocytes.
- Phosphorylation is crucial for NIC function, suggesting a regulatory mechanism.
- NIC may represent a functional component of nucleopore complexes involved in nucleocytoplasmic transport.