title: Na:Ca stoichiometry and cytosolic Ca-dependent activation of NCX in intact cardiomyocytes.
abstract: 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.
authors.affiliation: Department of Physiology, Loyola University Chicago, Stritch School of Medicine, 2160 South First Avenue, Maywood, IL 60153, USA. dbers@lumc.edu
authors.forename: Donald M
authors.initials: DM
authors.lastname: Bers
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Ginsburg
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*
chemical_list: D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium