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May 1, 1997The Journal of PhysiologyOpen Access

Measurement of sarcoplasmic reticulum Ca2+ content and sarcolemmal Ca2+ fluxes in isolated rat ventricular myocytes during spontaneous Ca2+ release

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Key result

Spontaneous release of calcium in overloaded rat ventricular myocytes effectively activates Ca2+ efflux and minimizes increases in diastolic tension, despite being potentially arrhythmogenic.

Population

Isolated rat ventricular myocytes loaded with the Ca(2+)-sensitive fluorescent indicator indo-1

Comparison

Raising external calcium concentration and… vs Baseline/lower external calcium concentration or…

Design

Preclinical

Authors

MDM.E. DíazUniversity of EdinburghATAndrew W. TraffordElectrophysiologySOStephen O’NeillQueen's University Belfast

Discussion

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Implication

Highlights potential protective role of spontaneous Ca2+ release against diastolic dysfunction; leaves open translation to human HF therapies.

Key Points

  • To measure sarcoplasmic reticulum (SR) calcium content and sarcolemmal calcium fluxes during spontaneous calcium release in calcium-overloaded cardiac myocytes.
  • Measured intracellular calcium concentration using the fluorescent indicator indo-1 alongside membrane currents in isolated, voltage-clamped rat ventricular myocytes.
  • Quantified SR calcium content using the integral of caffeine-evoked sodium-calcium exchange currents across varying extracellular calcium levels.
  • Elevating extracellular calcium increased the frequency of spontaneous releases without expanding SR calcium content beyond a defined threshold level.
  • Spontaneous calcium oscillations mediated a major portion of total calcium efflux via sodium-calcium exchange, while high extracellular calcium simultaneously reduced clearance rates.
  • Inhibition of spontaneous SR release increased resting intracellular calcium but maintained identical total calcium efflux, confirming spontaneous release acts to limit diastolic tension.

Structured PICO

P
Population
Isolated rat ventricular myocytes loaded with the Ca(2+)-sensitive fluorescent indicator indo-1
I
Intervention
Raising external calcium concentration ([Ca2+]o) and inhibiting spontaneous SR Ca2+ release
C
Comparator
Baseline/lower external calcium concentration or presence of spontaneous SR Ca2+ release
O
Outcome
Sarcoplasmic reticulum (SR) Ca2+ content, intracellular calcium concentration ([Ca2+]i), and Na(+)-Ca2+ exchange currentssurrogate

Spontaneous release of calcium in overloaded conditions is an effective mechanism to activate Ca2+ efflux and minimize increases in diastolic tension, despite being potentially arrhythmogenic.

Cite This Study

Díaz et al. (1997) studied Calcium overload in ventricular myocytes. Raising external calcium concentration ([Ca2+]o) and inhibiting spontaneous SR Ca2+ release vs. Baseline/quiescent cells was evaluated on Sarcoplasmic reticulum Ca2+ content and sarcolemmal Ca2+ fluxes. Spontaneous release of calcium in overloaded rat ventricular myocytes effectively activates Ca2+ efflux and minimizes increases in diastolic tension, despite being potentially arrhythmogenic.

synapsesocial.com/papers/6a158b1dd64fa333899fcacdhttps://doi.org/10.1111/j.1469-7793.1997.003bo.x
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Also Consider

Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1Spontaneous Ca2+ release from the sarcoplasmic reticulum limits Ca2+-dependent twitch potentiation in individual cardiac myocytes. A mechanism for maximum inotropy in the myocardium.1988 · 77 citations
  2. 2The role of [Ca2+]i and [Ca2+] sensitization in the caffeine contracture of rat myocytes: measurement of [Ca2+]i and [caffeine]i.1990 · 154 citations
  3. 3Spontaneous sarcoplasmic reticulum calcium release in rat and rabbit cardiac muscle: relation to transient and rested-state twitch tension.1988 · 34 citations
  4. 4Cellular and Subcellular Heterogeneity of [Ca 2+ ] i in Single Heart Cells Revealed by Fura-21987 · 347 citations
  5. 5Calcium Sparks: Elementary Events Underlying Excitation-Contraction Coupling in Heart Muscle1993 · 1,959 citations