Reverse mode of the sarcoplasmic reticulum calcium pump and load- dependent cytosolic calcium decline in voltage-clamped cardiac ventricular myocytes

T. R. Shannon, Kenneth S Ginsburg, Donald M Bers

Research output: Contribution to journalArticle

97 Scopus citations

Abstract

We have characterized [Ca](i) decline in voltage-clamped rabbit ventricular myocytes with progressive increases in sarcoplasmic reticulum (SR) calcium load. 'Backflux' through the SR calcium pump is a critical feature which allows realistically small values for SR calcium leak fluxes to be used. Total cytosolic calcium was calculated from the latter part of [Ca](i) decline using rate constants for cellular calcium buffers. Intra-SR calcium buffering characteristics were also deduced. We found that the net SR calcium pump flux and rate of [Ca](i) decline decreased as the SR free [Ca] rose, with pump parameters held constant. We have therefore characterized for the first time in intact myocytes both forward and reverse SR calcium pump kinetics as well as intra-SR calcium buffering and SR calcium leak. We conclude that the reverse flux through the SR calcium pump is an important factor in comprehensive understanding of dynamic SR calcium fluxes.

Original languageEnglish (US)
Pages (from-to)322-333
Number of pages12
JournalBiophysical Journal
Volume78
Issue number1
StatePublished - 2000
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics

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