Ca2+ sparks triggered by patch depolarization in rat heart cells

Stephen R. Shorofsky, Leighton T Izu, Withrow Gil Wier, C. William William Balke

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The goal of this study was to examine the relationship between Ca2+ entry through L-type Ca2+ channels and local [Ca2+](i) transients (Ca2+ sparks) in single rat cardiac ventricular cells. L-type Ca2+ channels were activated by depolarization of cell-attached membrane patches, and [Ca2+](i) was measured simultaneously as fluo 3 fluorescence using laser scanning confocal microscopy. Patch depolarization with Ca2+ as the charge career (10 or 110 mmol · L-1) significantly increased the probability of the occurrence of Ca12+ sparks (Ca2+ spark rate) only in the volume of cytoplasm located immediately beneath the membrane patch (basal Ca2+ spark rate, 119 Ca2+ sparks · cell- · s-1; patch depolarization Ca2+ spark rate, 610 Ca2+ sparks · cell-1 · s-1; P<.005). With Ba2+ in the pipette solution (10 mmol · L-1), patch depolarization was not associated with an increased Ca2+ spark rate at the position of the pipette or at any other sites distant from the pipette. Therefore, Ca2+ entry and not voltage per se was a necessary event for the occurrence of Ca2+ sparks. Under identical experimental conditions, patch depolarization experiments opened single L-type Ca2+ channels with a single-channel conductance of 19 pS with Ba2+ as the charge career. Although single-channel openings could not be resolved when Ca2+ was the charge carrier, ensemble averages yielded an inward current of up to 0.75 pA. The results suggest that voltage-activated Ca2+ entry through one or a small number of L type Ca2+ channels triggers the release of Ca2+ only from the sarcoplasmic reticulum in direct proximity to those L-type Ca2+ channels. The relatively low probability of triggering Ca2+ sparks may have resulted from some alteration of excitation-contraction coupling associated with the technique of the cell- attached patch clamp.

Original languageEnglish (US)
Pages (from-to)424-429
Number of pages6
JournalCirculation Research
Volume82
Issue number4
StatePublished - Mar 9 1998
Externally publishedYes

Fingerprint

Excitation Contraction Coupling
Sarcoplasmic Reticulum
Confocal Microscopy
Cytoplasm
Fluorescence
Cell Membrane
Membranes
Fluo-3

Keywords

  • Ca spark
  • Excitation-contraction coupling
  • Heart
  • Single L-type Ca channel

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Shorofsky, S. R., Izu, L. T., Wier, W. G., & William Balke, C. W. (1998). Ca2+ sparks triggered by patch depolarization in rat heart cells. Circulation Research, 82(4), 424-429.

Ca2+ sparks triggered by patch depolarization in rat heart cells. / Shorofsky, Stephen R.; Izu, Leighton T; Wier, Withrow Gil; William Balke, C. William.

In: Circulation Research, Vol. 82, No. 4, 09.03.1998, p. 424-429.

Research output: Contribution to journalArticle

Shorofsky, SR, Izu, LT, Wier, WG & William Balke, CW 1998, 'Ca2+ sparks triggered by patch depolarization in rat heart cells', Circulation Research, vol. 82, no. 4, pp. 424-429.
Shorofsky SR, Izu LT, Wier WG, William Balke CW. Ca2+ sparks triggered by patch depolarization in rat heart cells. Circulation Research. 1998 Mar 9;82(4):424-429.
Shorofsky, Stephen R. ; Izu, Leighton T ; Wier, Withrow Gil ; William Balke, C. William. / Ca2+ sparks triggered by patch depolarization in rat heart cells. In: Circulation Research. 1998 ; Vol. 82, No. 4. pp. 424-429.
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