Article,

Na:Ca stoichiometry and cytosolic Ca-dependent activation of NCX in intact cardiomyocytes.

, and .
Ann. N. Y. Acad. Sci., (March 2007)
DOI: 10.1196/annals.1387.060

Abstract

We are studying both Na:Ca exchange stoichiometry and cytosolic Ca (Cai)-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 Cai-dependent NCX regulation as a static process (dependent on instantaneous local Cai). 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.

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