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Assessment of Sarcoplasmic Reticulum Calcium Reserve and Intracellular Diastolic Calcium Removal in Isolated Ventricular Cardiomyocytes
Published on: September 18, 2017
Dynamic calcium movement inside cardiac sarcoplasmic reticulum during release.
Eckard Picht1, Aleksey V Zima, Thomas R Shannon
1Department of Pharmacology, University of California-Davis, 451 Health Sciences Drive, Davis, CA 95616, USA.
Circulation Research
|February 12, 2011
Summary
Intra-sarcoplasmic reticulum (SR) calcium dynamics reveal rapid diffusion during normal heartbeats, but spatial gradients emerge during spontaneous calcium release events. These findings impact understanding of heart cell calcium handling and arrhythmias.
Area of Science:
- Cardiovascular Physiology
- Cellular Biology
- Biophysics
Background:
- Intra-sarcoplasmic reticulum (SR) free calcium ([Ca]SR) is crucial for regulating SR calcium release and cardiac function.
- Understanding the spatiotemporal dynamics of [Ca]SR is vital for comprehending normal and arrhythmogenic cardiac events.
- Current knowledge regarding [Ca]SR spatiotemporal dynamics is limited.
Purpose of the Study:
- To directly measure local [Ca]SR with subsarcomeric spatiotemporal resolution.
- To analyze [Ca]SR dynamics during both normal SR calcium release and spontaneous calcium sparks.
- To evaluate the quantitative implications of spatial [Ca]SR gradients.
Main Methods:
- Simultaneous measurement of cytosolic calcium and [Ca]SR using fluorescence recovery after photobleaching (FRAP) in rabbit ventricular myocytes.
- Direct measurement of [Ca]SR and cytosolic calcium.
- Utilized a computational model to interpret findings.
Main Results:
- No significant [Ca]SR gradients were detected between junctional and free SR during normal global calcium release.
- Clear spatiotemporal [Ca]SR gradients were observed during isolated calcium blinks.
- Intra-SR calcium diffusion is faster longitudinally than transversely and slower than in the cytosol.
- Local intra-SR calcium diffusion is influenced by SR connectivity.
Conclusions:
- Rapid intra-SR calcium diffusion limits spatial [Ca]SR gradients during normal excitation-contraction coupling.
- Spatiotemporal [Ca]SR gradients are evident during calcium sparks, providing insights into SR calcium dynamics.
- These findings have significant implications for myocyte SR calcium handling, synchrony, and the potential for spontaneous contractions leading to arrhythmias.
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