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PMID: 10620296 Published · ppublish English Journal Article Research Support, U.S. Gov't, P.H.S.

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

Biophysical journal ·Vol. 78 ·No. 1 ·2000-01-00 ·Pages 322-33

Shannon TR, Ginsburg KS, Bers DM

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.

MeSH Terms
Animals Calcium/metabolism Calcium-Transporting ATPases/metabolism Cells, Cultured Cytosol/metabolism Heart/physiology Heart Ventricles Intracellular Membranes/physiology,ultrastructure Kinetics Myocardium/metabolism Patch-Clamp Techniques Rabbits Sarcoplasmic Reticulum/enzymology,ultrastructure Troponin/metabolism
Chemicals
Troponin Calcium-Transporting ATPases Calcium
Authors & Affiliations
3 authors, click to expand affiliations / ORCID
Shannon T R
Department of Physiology, Loyola University Chicago, Maywood, Illinois, 60153, USA.
Ginsburg K S
Bers D M
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Article Info
Journal
Biophysical journal
Abbr.
Biophys J
ISSN
0006-3495
DOI
10.1016/S0006-3495(00)76595-7
Published
2000-01-00
Pages
322-33
Language
English
Region
United States
NLM ID
0370626
PMCID
PMC1300640
Subset
IM
Grants
NHLBI NIH HHS · HL09412 · United States
NHLBI NIH HHS · HL30077 · United States
External Links
PubMed source DOI: 10.1016/S0006-3495(00)76595-7 PMC Full Text View journal details
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