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Analysis of Tubular Membrane Networks in Cardiac Myocytes from Atria and Ventricles
Published on: October 15, 2014
Coupled gating between individual cardiac ryanodine calcium release channels
1Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Bratislava. umfgonds@kramare.savba.sk
General Physiology and Biophysics
|August 10, 2002
Summary
Researchers investigated ryanodine receptor calcium release (RyR2) channel interactions in cardiac muscle. They discovered coupled RyR2 channels within cardiac sarcoplasmic vesicles, impacting muscle excitation-contraction coupling.
Area of Science:
- Cardiovascular Physiology
- Molecular Biophysics
- Membrane Biology
Background:
- Excitation-contraction coupling in cardiac muscle relies on ryanodine receptor calcium release (RyR2) channels.
- Understanding RyR2 channel interactions is crucial for cardiac function.
- Previous methods for studying RyR2 channel fusion into bilayer lipid membranes (BLMs) had limitations.
Purpose of the Study:
- To investigate interactions between RyR2 channels during cardiac excitation-contraction coupling.
- To improve the method for fusing cardiac sarcoplasmic vesicles into BLMs for studying RyR2 channel behavior.
Main Methods:
- Utilized bilayer lipid membrane (BLM) technology.
- Enhanced cardiac sarcoplasmic vesicle fusion into BLMs by increasing fusion gradient and using chloride ions (up to 1.2 mol/l).
- Fused vesicles directly into forming BLMs, observing channel behavior in varying calcium concentrations.
Main Results:
- Achieved increased probability of fusing vesicles containing 2-7 RyR2 channels into BLMs.
- Observed that approximately 10% of RyR2 channels exhibited coupled gating, not independent gating.
- Coupled RyR2 channels showed double conductance (191 ± 15 pS) compared to non-coupled channels (93 ± 10 pS) in 53 mmol/l calcium.
- Coupled channel activity was sensitive to ryanodine and ruthenium red, similar to single RyR2 channels.
Conclusions:
- Cardiac sarcoplasmic vesicles contain both single and coupled RyR2 channels.
- Coupled RyR2 channels play a role in cardiac excitation-contraction coupling.
- The improved BLM fusion method facilitates the study of RyR2 channel interactions.
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