Sarcoplasmic reticulum Ca2+ refilling controls recovery from Ca2+-induced Ca2+ release refractoriness in heart muscle

Peter Szentesi, Christophe Pignier, Marcel Egger, Evangelia G. Kranias, Ernst Niggli

Research output: Article

70 Citations (Scopus)

Abstract

In cardiac muscle Ca2+-induced Ca2+ release (CICR) from the sarcoplasmic reticulum (SR) is initiated by Ca2+ influx via L-type Ca2+ channels. At present, the mechanisms underlying termination of SR Ca2+ release, which are required to ensure stable excitation-contraction coupling cycles, are not precisely known. However, the same mechanism leading to refractoriness of SR Ca2+ release could also be responsible for the termination of CICR. To examine the refractoriness of SR Ca2+ release, we analyzed Na+-Ca2+ exchange currents reflecting cytosolic Ca2+ signals induced by UV-laser flash-photolysis of caged Ca2+. Pairs of UV flashes were applied at various intervals to examine the time course of recovery from CICR refractoriness. In cardiomyocytes isolated from guinea-pigs and mice, β-adrenergic stimulation with isoproterenol-accelerated recovery from refractoriness by ≈2-fold. Application of cyclopiazonic acid at moderate concentrations (< 10 μmol/L) slowed down recovery from refractoriness in a dose-dependent manner. Compared with cells from wild-type littermates, those from phospholamban knockout (PLB-KO) mice exhibited almost 5-fold accelerated recovery from refractoriness. Our results suggest that SR Ca2+ refilling mediated by the SR Ca2+-pump corresponds to the rate-limiting step for recovery from CICR refractoriness. Thus, the Ca 2+ sensitivity of CICR appears to be regulated by SR Ca2+ content, possibly resulting from a change in the steady-state Ca2+ sensitivity and in the gating kinetics of the SR Ca2+ release channels (ryanodine receptors). During Ca2+ release, the concomitant reduction in Ca2+ sensitivity of the ryanodine receptors might also underlie Ca2+ spark termination by deactivation.

Original languageEnglish
Pages (from-to)807-813
Number of pages7
JournalCirculation research
Volume95
Issue number8
DOIs
Publication statusPublished - okt. 15 2004

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ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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