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Na:Ca Stoichiometry and Cytosolic Ca‐Dependent Activation of NCX in Intact Cardiomyocytes
Author(s) -
BERS DONALD M.,
GINSBURG KENNETH S.
Publication year - 2007
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1387.060
Subject(s) - stoichiometry , cytosol , chemistry , biophysics , sodium calcium exchanger , subcellular localization , myocyte , microbiology and biotechnology , calcium , cytoplasm , biochemistry , biology , enzyme , organic chemistry
We are studying both Na:Ca exchange stoichiometry and cytosolic [Ca] ([Ca] i )‐dependent regulation of Na–Ca exchange (NCX) in intact rabbit ventricular myocytes. Analysis of NCX fluxes in subcellular systems strongly supports a dominant 3Na:1Ca exchange, and our measurements in intact cells confirm this. However, in intact native cells, local ion gradients and other factors complicate the process of inferring stoichiometry. From a functional viewpoint, NCX stoichiometry is near 3:1 but is affected by ion accumulation/depletion as well as non‐NCX fluxes. We and others have viewed [Ca] i ‐dependent NCX regulation as a static process (dependent on instantaneous local [Ca] i ). However, evidence from subcellular and expression systems shows the process to be dynamic, and our observations confirm this to be the case in intact cardiac cells as well.